Publications

Research Papers

Researchmap:Link
  • Yusuke Oteki, Yasushi Shoji, Naoya Miyashita, Yoshitaka Okada, “Dependence of the radiative lifetime on the type-II band offset in GaAsxSb1−x/GaAs quantum dots including effects of photoexcited carriers”, Journal of Applied Physics 132, 134402 (2022)
  • Myeongok Kim, Maxime Giteau, Nazmul Ahsan, Naoya Miyashita, Logu Thirumalaisamy, Chen Chen, Joan M Redwing, Yoshitaka Okada, “Co-deposition of MoS2 films by reactive sputtering and formation of tree-like structures” Nanotechnology 33, 345708(2022)
  • Haibin Wang, Shoichiro Nakao, Naoya Miyashita, Yusuke Oteki, Maxime Giteau, Yoshitaka Okada, Tatsuya Takamoto, Hidenori Saito, Shinichi Magaino, Katsuhiko Takagi, Tetsuya Hasegawa, Takaya Kubo, Takumi Kinoshita, Jotaro Nakazaki, Hiroshi Segawa, “Spectral Splitting Solar Cells Constructed with InGaP/GaAs Two-Junction Subcells and Infrared PbS Quantum Dot/ZnO Nanowire Subcells”
    ACS Energy Letters 7, 2477-2485 (2022)
  • Yaxing Zhu, Shigeo Asahi, Naoya Miyashita, Yoshitaka Okada, Takashi Kita, “Diffusion photocurrent influenced by intraband excitation in an intermediate band solar cell with type-I band alignment”
    Japanese Journal of Applied Physics 61, 074002  (2022)
  • S. Suba Viveka, T. Logu, N. Ahsan, K. Asokan, S. Kalainathan, K. Sethuraman, Y. Okada, “Study of sub-band states formation in the optical band gap of CuGaS2 thin films by electronic excitations”
    Journal of Physics and Chemistry of Solids 164, 110636 (2022)
  • Karthikeyan Vijayan, S. P. Vijayachamundeeswari, Kalainathan Sivaperuman, Nazmul Ahsan, Thirumalaisamy Logu, Yoshitaka Okada, “A review on advancements, challenges, and prospective of copper and non-copper based thin-film solar cells using facile spray pyrolysis technique”
    Solar Energy 234, 81-102 (2022)
  • Myeongok Kim, Nazmul Ahsan, Zacharie Jehl, Yudania Sánchez, Yoshitaka Okada, “Properties of sputter-grown CuGaS2 absorber and CuGaS2/Cd1-xZnxS buffer heterointerface for solar cell application”
    Thin Solid Films 139063-139063 (2021)
  • S. Suba Viveka, T. Logu, N. Ahsan, J. Karthikeyan, P. Murugan, M. Sampath, S. Kalainathan, Arunava Gupta, Y. Okada, K. Sethuraman, “Fe-doped CuGaS2 (CuGa1-xFexS2) – Detailed analysis of the intermediate band optical response of chalcopyrite thin films based on first principle calculations and experimental studies”
    Materials Science in Semiconductor Processing 136 (2021)
  • Tetsuya Nakamura, Warakorn Yanwachirakul, Mitsuru Imaizumi, Masakazu Sugiyama, Hidefumi Akiyama, Yoshitaka Okada, “Reducing Shockley-Read-Hall recombination losses in the depletion region of a solar cell by using a wide-gap emitter layer”
    Journal of Applied Physics 130(15) (2021)
  • Yaxing Zhu, Shigeo Asahi, Naoya Miyashita, Yoshitaka Okada, Takashi Kita, “Two-photon photocurrent spectra of InAs quantum dot-in-well intermediated-band solar cells at room temperature”
    Journal of Applied Physics 130(12) (2021)
  • Tomoya Koga, Ryo Tamaki, Xiang Meng, Yushin Numazawa, Yosuke Shimura, Nazmul Ahsan, Yoshitaka Okada, Akihiro Ishida, Hirokazu Tatsuoka, “Fine structural and photoluminescence properties of Mg2Si nanosheet bundles rooted on Si substrates”
    Japanese Journal of Applied Physics 60(SB) (2021)
  • Tomah Sogabe, Chao-Yu Hung, Ryo Tamaki, Stanko Tomić, Koichi Yamaguchi, Ned Ekins-Daukes, Yoshitaka Okada, “Experimental demonstration of energy-transfer ratchet intermediate-band solar cell”
    Communications Physics 4(1) (2021)
  • Yaxing Zhu, Shigeo Asahi, Kohei Watanabe, Naoya Miyashita, Yoshitaka Okada, Takashi Kita, “Two-step excitation induced photovoltaic properties in an InAs quantum dot-in-well intermediate-band solar cell”
    Journal of Applied Physics 129(7) (2021)
  • Yasushi Shoji, Ryo Tamaki, Yoshitaka Okada, “Temperature dependence of carrier extraction processes in gasb/algaas quantum nanostructure intermediate-band solar cells”
    Nanomaterials 11(2) 1-13 (2021)
  • Maxime Giteau, Edouard De Moustier, Daniel Suchet, Hamidreza Esmaielpour, Hassanet Sodabanlu, Kentaroh Watanabe, Stéphane Collin, Jean François Guillemoles, Yoshitaka Okada, “Identification of surface and volume hot-carrier thermalization mechanisms in ultrathin GaAs layers”
    Journal of Applied Physics 128(19) (2020)
  • Iván Lombardero, Mario Ochoa, Naoya Miyashita, Yoshitaka Okada, Carlos Algora, “Theoretical and experimental assessment of thinned germanium substrates for III–V multijunction solar cells”
    Progress in Photovoltaics: Research and Applications 28(11) 1097-1106 (2020)
  • Bernice Mae Yu Jeco-Espaldon, Haibin Wang, Achilles E. Espaldon, Takaya Kubo, Hiroshi Segawa, Nazmul Ahsan, Yoshitaka Okada, “Application of perovskite quantum dots in carrier redistribution in III-V multijunction solar cells with luminescent coupling effect”
    Journal of Photonics for Energy 10(4) (2020)
  • Logu Thirumalaisamy, Nazmul Ahsan, Kalainathan Sivaperuman, Myeongok Kim, Sethuraman Kunjithapatham, Yoshitaka Okada, “Engineering of sub-band in CuGaS2 thin films via Mo doping by chemical spray pyrolysis route”
    Thin Solid Films 709 138252-138252 (2020)
  • Meita Asami, Kasidit Toprasertpong, Kentaroh Watanabe, Yoshiaki Nakano, Yoshitaka Okada, Masakazu Sugiyama, “Comparison of Effective Carrier Mobility between Wire on Well and Planar Superlattice Using Time-of-Flight Measurement”
    IEEE Journal of Photovoltaics 10(4) 1008-1014 (2020)
  • Bernice Mae F. Yu Jeco, Hao Xu, Masakazu Sugiyama, Yoshitaka Okada, “Luminescence imaging of III-V multijunction solar cells with luminescent coupling effect”
    2020 47th IEEE Photovoltaic Specialists Conference (PVSC) 0584-0586 (2020)
  • Tetsuya Nakamura, Mitsuru Imaizumi, Hidefumi Akiyama, Yoshitaka Okada, “Practical target values of Shockley–Read–Hall recombination rates in state‐of‐the‐art triple‐junction solar cells for realizing conversion efficiencies within 1% of the internal radiative limit”
    Progress in Photovoltaics: Research and Applications 28(5) 417-424 (2020)
  • Maxime Giteau, Kentaroh Watanabe, Naoya Miyashita, Hassanet Sodabanlu, Fabien Atlan, Daniel Suchet, Stéphane Collin, Jean-François Guillemoles, Yoshitaka Okada, “Fabrication and optical characterization of ultrathin III-V transferred heterostructures for hot-carrier absorbers”
    Proceedings of SPIE – The International Society for Optical Engineering, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IX (SPIE OPTO) 11275 (2020)
  • Ryo Tamaki, Yasushi Shoji, Laurent Lombez, Jean-François Guillemoles, Yoshitaka Okada, “Quasi-Fermi level splitting in InAs quantum-dot solar cells from photoluminescence measurements”
    Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IX (2020)
  • M. Giteau, K. Watanabe, N. Miyashita, H. Sodabanlu, D. Suchet, S. Collin, J.-F. Guillemoles, Y. Okada, “Designing better absorbers for hot-carrier solar cells”
    Proceedings of SPIE – The International Society for Optical Engineering 11275 (2020)
  • Hamidreza Esmaielpour, Maxime Giteau, Amaury Delamarre, François Gibelli, Dac Trung Nguyen, Nicolas Cavassilas, Yoshitaka Okada, Jean François Guillemoles, Laurent Lombez, Daniel Suchet, “Advanced analysis for hot-carriers photoluminescence spectrum”
    Proceedings of SPIE – The International Society for Optical Engineering 11275 (2020)
  • Y. Shoji, K. Watanabe, Y. Okada, “Photoabsorption improvement in multi-stacked InGaAs/GaAs quantum dot solar cell with a light scattering rear texture”
    Solar Energy Materials and Solar Cells 204 (2020)
  • N. Miyashita, Yilun He, N. Ahsan, and Y. Okada, “Anneal mediated deep-level dynamics in GaInNAsSb dilute nitrides lattice-matched to GaAs”, Journal of Applied Physics, 126, 143104 (2019); DOI: 10.1063/1.5111588
  • Hao Xu, Amaury Delamarre, Bernice Mae F. Yu Jeco, Hugh Johnson, Kentaroh Watanabe, Yoshitaka Okada, Jean François Guillemoles, Yoshiaki Nakano, Masakazu Sugiyama, “Current transport efficiency analysis of multijunction solar cells by luminescence imaging”
    Progress in Photovoltaics: Research and Applications 27(10) 835-843 (2019)
  • B. Behaghel, R. Tamaki, H.-L. Chen, P. Rale, L. Lombez, Y. Shoji, A. Delamarre, A. Cattoni, S. Collin, Y. Okada, J.-F. Guillemoles, “A hot-carrier assisted InAs/AlGaAs quantum-dot intermediate-band solar cell”
    Semiconductor Science and Technology 34 084001 (2019)
  • Naoya Miyashita, Yilun He, Takaaki Agui, Hiroyuki Juso, Tatsuya Takamoto, Yoshitaka Okada, “Inverted Lattice-Matched Triple Junction Solar Cells with 1.0 eV GaInNAsSb Subcell by MOCVD/MBE Hybrid Growth”
    IEEE Journal of Photovoltaics 9(3) 666-672 (2019)
  • Muriel Bouttemy, Damien Aureau, Mathieu Frégnaux, Yasushi Shoji, Zacharie Jehl, Daniel Suchet, Jean François Guillemoles, Arnaud Etcheberry, Yoshitaka Okada, “Nanoscale Wet Chemical Engineering of III-V Quantum Dots for Emerging Solar Applications”
    ECS Transactions 89(4) 37-46 (2019)
  • Bernice Mae F Yu Jeco, Elias Veinberg-Vidal, Laura Vauche, Katsuhisa Yoshida, Ryo Tamaki, Nazmul Ahsan, Yoshitaka Okada, “Luminescent coupling effect in wafer-bonded III-V on silicon multijunction solar cells”Journal of Photonics for Energy 9(1) 015504 (2019)
  • Bernice Mae F Yu Jeco, Elias Veinberg-Vidal, Laura Vauche, Nazmul Ahsan, Yoshitaka Okada, “Temperature dependence of wafer-bonded III-V on silicon multijunction solar cells with luminescent coupling effect”
    Journal of Photonics for Energy 9(1) 015503 (2019)
  • Tomohiro Hirata, Dinesh Bahadur Malla, Katsuyoshi Sakamoto, Koichi Yamaguchi, Yoshitaka Okada, Tomah Sogabe, “Smart Grid Optimization by Deep Reinforcement Learning over Discrete and Continuous Action Space”
    Bulletin of Networking, Computing, Systems, and Software 8(1) 19-22 (2019)
  • Yalei Huang, Ryo Tamaki, Peiling Yuan, Yuki Kumazawa, Nanae Atsumi, Vimal Saxena, Nazmul Ahsan, Yoshitaka Okada, Yasuhiro Hayakawa, Hirokazu Tatsuoka, “Synthesis, structural and photoluminescence properties of Mg<inf>2</inf>Si/Si nanocomposites consisting of Si nanosheet bundles and Mg<inf>2</inf>Si deposits”
    Japanese Journal of Applied Physics 58(SB) (2019)
  • Maxime Giteau, Daniel Suchet, Stéphane Collin, Jean-François Guillemoles, Yoshitaka Okada, “Detailed balance calculations for hot-carrier solar cells: coupling high absorptivity with low thermalization through light trapping”
    EPJ Photovoltaics 10 1 (2019)
  • Maxime Giteau, Kentaroh Watanabe, Naoya Miyashita, Hassanet Sodabanlu, Julie Goffard, Amaury Delamarre, Daniel Suchet, Ryo Tamaki, Zacharie Jehl, Laurent Lombez, Masakazu Sugiyama, Andrea Cattoni, Stéphane Collin, Jean-François Guillemoles, Yoshitaka Okada, “Light absorption enhancement in ultra-thin layers for hot-carrier solar cells: first developments towards the experimental demonstration of an enhanced hot-carrier effect with light trapping”
    SPIE Proceedings, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VIII 10913 109130D (2019)
  • Hiroji Hosokawa, Ryo Tamaki, Takuya Sawada, Akinori Okonogi, Haruyuki Sato, Yuhei Ogomi, Shuzi Hayase, Yoshitaka Okada, and Toshihiro Yano , “Solution-processed intermediate-band solar cells with lead sulfide quantum dots and lead halide perovskites”, Nature Communicationsvolume 10, Article number: 43 (2019); DOI: https://doi.org/10.1038/s41467-018-076-3
  • Y. Shoji, K. Watanabe, Y. Okada, “Photoabsorption improvement in multi-stacked InGaAs/GaAs quantum dot solar cell with a light scattering rear texture”, Solar Energy Materials and Solar Cells, 204, 110216 (2019)
  • Yilun He, Naoya Miyashita, and Yoshitaka Okada, “N–H-related deep-level defects in dilute nitride semiconductor GaInNAs for four-junction solar cells”, Japanese Journal of Applied Physics 57, 08RD11 (2018);
  • Naoya Miyashita, Yilun He, Nazmul Ahsan, Takaaki Agui, Hiroyuki Juso, Tatsuya Takamoto, and Yoshitaka Okada, “Incorporation of hydrogen into MBE-grown dilute nitride GaInNAsSb layers in a MOCVD growth ambient”, Solar Energy Materials and Solar Cells 185, 359-363 (2018);
  • Tatsuya Nakata, Kentaroh Watanabe, Naoya Miyashita, Hassanet Sodabanlu, Maxime Giteau, Yoshiaki Nakano, Yoshitaka Okada, and Masakazu Sugiyama, “Thin-film multiple-quantum-well solar cells fabricated by epitaxial lift-off process”, Japanese Journal of Applied Physics 57, 08RF03 (2018);
  • Naoya Miyashita, Benoît Behaghel, Jean-François Guillemoles, and Yoshitaka Okada, “Enhancement of photocurrent in epitaxial lift-off thin-film GaInNAsSb solar cells due to light-confinement structure”, Applied Physics Express 11, 072301 (2018);
  • Daniel Suchet, Amaury Delamarre, Nicolas Cavassilas, Zacharie Jehl, Yoshitaka Okada, Masakazu Sugiyama, and Jean-Francois Guillemoles, “Analytical optimization of intermediate band systems: Achieving the best of two worlds”, Prog Photovolt Res Appl. 2018;1–8. DOI: 10.1002/pip.3020 (2018);
  • Bernice Mae F. Yu Jeco, Tomah Sogabe, Nazmul Ahsan, and Yoshitaka Okada, “Temperature dependence of luminescence coupling effect in InGaP/GaAs/Ge triple junction solar cells”, J. of Photonics for Energy 8(2), 022602 (2018); https://doi.org/10.1117/1.JPE.8.022602
  • Md. Dulal Haque, Norihiko Kamata, Takeshi Fukuda, Zentaro Honda, Shuhei Yagi, Hiroyuki Yaguchi, and Yoshitaka Okada, “Nonradiative recombination centers in GaAs:N δ-doped superlattice revealed by two-wavelength-excited photoluminescence”, Journal of Applied Physics 123, 161426 (2018); https://doi.org/10.1063/1.5011311
  • Samy Almosni, Amaury Delamarre, Zacharie Jehl, Daniel Suchet, Ludmila Cojocaru, Maxime Giteau, Benoit Behaghel, Anatole Julian, Camille Ibrahim, Léa Tatry, Haibin Wang, Takaya Kubo, Satoshi Uchida, Hiroshi Segawa, Naoya Miyashita, Ryo Tamaki, Yasushi Shoji, Katsuhisa Yoshida, Nazmul Ahsan, Kentaro Watanabe, Tomoyuki Inoue, Masakazu Sugiyama, Yoshiaki Nakano, Tomofumi Hamamura, Thierry Toupance, Céline Olivier, Sylvain Chambon, Laurence Vignau, Camille Geffroy, Eric Cloutet, Georges Hadziioannou, Nicolas Cavassilas, Pierre Rale, Andrea Cattoni, Stéphane Collin, François Gibelli, Myriam Paire, Laurent Lombez, Damien Aureau, Muriel Bouttemy, Arnaud Etcheberry, Yoshitaka Okada, and Jean-François Guillemoles, “Material challenges for solar cells in the twenty-first century: directions in emerging technologies”, Science and Technology of Advanced Materials 19(1), 336–369 (2018); https://doi.org/10.1080/14686996.2018.1433439
  • Peiling Yuan, Ryo Tamaki, Shinya Kusazaki, Nanae Atsumi, Yuya Saito, Yuki Kumazawa, Nazmul Ahsan, Yoshitaka Okada, Akihiro Ishida, and Hirokazu Tatsuoka, “Structural and photoluminescence properties of Si-based nanosheet bundles rooted on Si substrates”, Japanese Journal of Applied Physics 57, 04FJ01 (2018);
  • Amaury Delamarre, Daniel Suchet, Nicolas Cavassilas, Yoshitaka Okada, Masakazu Sugiyama, and Jean-François Guillemoles, “Non-ideal nanostructured intermediate band solar cells with an electronic ratchet”, SPIE OPTO Proceedings 10527, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VII; 105270R (2018); https://doi.org/10.1117/12.2287716
  • Ryo Tamaki, Yasushi Shoji, Laurent Lombez, Jean-François Guillemoles, and Yoshitaka Okada, “Quantitative analysis of InAs quantum dot solar cells by photoluminescence spectroscopy”, SPIE OPTO Proceedings 10527, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VII; 105270S (2018) https://doi.org/10.1117/12.2291465
  • Daniel Suchet, Amaury Delamarre, Nicolas Cavassilas, Zacharie Jehl, Yoshitaka Okada, Masakazu Sugiyama, and Jean-François Guillemoles, “Voltage preservation in Intermediate Band Solar Cells”, Applied Physics, arXiv:1802.05238v1 (2018);
  • Daniel Suchet, Zacharie Jehl, Yoshitaka Okada, and Jean-Francois Guillemoles, “Influence of Hot-Carrier Extraction from a Photovoltaic Absorber: An Evaporative Approach”, Phys. Rev. Applied 8 (3), 034030 (2017); DOI:https://doi.org/10.1103/PhysRevApplied.8.034030
  • Ryo Tamaki, Takeshi Toyoda, Yoichi Tamura, Akinari Matoba, Toshiharu Minamikawa, Masayuki Tokuda, Megumi Masui, and Yoshitaka Okada, “Hybrid Photovoltaic and Thermoelectric Module for High Concentration Solar System”, AIP Conference Proceedings 1881, 100002 (2017); DOI: 10.1002/pip.2641
  • Bernice Mae F. Yu Jeco, Tomah Sogabe, Ryo Tamaki, Nazmul Ahsan, and Yoshitaka Okada, “Impact of optically nonuniform luminescence coupling effect to the limiting cell conversion efficiency in InGaP/GaAs/Ge triple junction solar cell”, Journal of Photonics for Energy 7, 035501 (2017); DOI: 10.1002/pip.2641
  • T. Kada, S. Asahi, T. Kaizu, Y. Harada, R. Tamaki, Y. Okada, and T. Kita, “Efficient two-step photocarrier generation in bias-controlled InAs/GaAs quantum dot superlattice intermediate-band solar cells”, Scientific Reports 7, 5865 (2017); DOI: 10.1002/pip.2641
  • Shunya Naito, Katsuhisa Yoshida, Naoya Miyashita, Ryo Tamaki, Takuya Hoshii, and Yoshitaka Okada, “Effect of Si doping and sunlight concentration on the performance of InAs/GaAs quantum dot solar cells”, Journal of Photonics for Energy 7, 025505 (2017); DOI: 10.1002/pip.2641
  • Yasushi Shoji, Ryo Tamaki, and Yoshitaka Okada, “Multi-stacked GaSb/GaAs type-II quantum nanostructures for application to intermediate band solar cells”, AIP Advances 7, 065305 (2017); DOI: 10.1002/pip.2641
  • Peiling Yuan, Ryo Tamaki, Hiroaki Suzuki, Kenta Sasaki, Makoto Nakayama, Yuya Saito, Shinya Kusazaki, Yuki Kumazawa, Xiang Meng, Nazmul Ahsan, Yoshitaka Okada, and Hirokazu Tatsuoka, “Synthesis of flowerlike Si nanostructures on Si substrates”, Japanese Journal of Applied Physics 56, 05DE05 (2017); DOI: 10.1002/pip.2641
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Improvement of 1.0 eV GaInNAsSb solar cell performance upon optimal annealing”, Physica Status Solidi A, 214, 1600586 (2017);
  • Zacharie Jehl, Daniel Suchet, Anatole Julian, Cyril Bernard, Naoya Miyashita, Francois Gibelli, Yoshitaka Okada, and Jean-Francois Guillemoles, “Modeling and characterization of double resonant tunneling diodes for application as energy selective contacts in hot carrier solar cells”, Proceedings of SPIE 10099, 100990N (2017);
  • A. Julian, Z. Jehl, N. Miyashita, Y. Okada, and J.-F. Guillemoles, “Insights on energy selective contacts for thermal energy harvesting using double resonant tunneling contacts and numerical modeling”, Superlattices and Microstructures 100, 749 (2016); DOI: 10.1002/pip.2641
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Generation and collection of photocarriers in dilute nitride GaInNAsSb solar cells”, Progress in Photovoltaics: Research and Applications 24, 28-37 (2016); DOI: 10.1002/pip.2641
  • Chao-Yu Hung, Tomah Sogabe, Naoya Miyashita, and Yoshitaka Okada, “Growth of ErAs nanodots by molecular beam epitaxy for application to tunneling junctions in multijunction solar cells”, Japanese Journal of Applied Phyisics 55, 021201 (2016);
  • E. López, A. Datas, I. Ramiro, P.G. Linares, E. Antolín, I. Artacho, A. Martí, A. Luque, Y. Shoji, T. Sogabe, A. Ogura, and Y. Okada, “Demonstration of the operation principles of intermediate band solar cells at room temperature”, Solar Energy Materials and Solar Cells 149, 15 (2016);
  • Daniel J. Farrell, Hassanet Sodabanlu, Yunpeng Wang, Masakazu Sugiyama, and Yoshitaka Okada, “A hot-electron thermophotonic solar cell demonstrated by thermal up-conversion of sub-bandgap photons”, NATURE COMMUNICATIONS 6, 8685 (2015);
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Evaluation of concentrator photovoltaic properties of GaInNAsSb solar cells for multijunction solar cell applications”, Japanese Journal of Applied Physics 54, 08KE06 (2015); http://dx.doi.org/10.7567/JJAP.54.08KE06
  • Tomoya Suzuki, Kazuki Osada, Shuhei Yagi, Shunya Naitoh, Yasushi Shoji, Yasuto Hijikata, Yoshitaka Okada, and Hiroyuki Yaguchi, “Molecular beam epitaxial growth of intermediate-band materials based on GaAs: N δ-doped superlattices”, Japanese Journal of Applied Physics 54, 08KA07 (2015); http://dx.doi.org/10.7567/JJAP.54.08KA07
  • Kazuki Osada, Tomoya Suzuki, Shuhei Yagi, Shunya Naitoh, Yasushi Shoji, Yasuto Hijikata, Yoshitaka Okada, and Hiroyuki Yaguchi, “Control of intermediate-band configuration in GaAs: N δ-doped superlattice”, Japanese Journal of Applied Physics 54, 08KA04 (2015),http://dx.doi.org/10.7567/JJAP.54.08KA04
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Generation and collection of photocarriers in dilute nitride GaInNAsSb solar cells”, Progress in Photovoltaics: Research and Applications (2015); DOI: 10.1002/pip.2641
  • Y. Okada, N. J. Ekins-Daukes, T. Kita, R. Tamaki, M. Yoshida, A. Pusch, O. Hess, C. C. Phillips, D. J. Farrell, K. Yoshida, N. Ahsan, Y. Shoji, T. Sogabe, and J-F. Guillemoles, “Intermediate band solar cells: Recent progress and future directions”, Applied Physics Reviews 2, 021302 (2015); http://dx.doi.org/10.1063/1.4916561
  • T. Kada, S. Asahi, T. Kaizu, Y. Harada, T. Kita, R. Tamaki, Y. Okada, and K Miyano, “Two-step photon absorption in InAs/GaAs quantum-dot superlattice solar cells”, Physical Review B 91, 201303 (2015);http://dx.doi.org/10.1103/PhysRevB.91.201303
  • Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “Electron Barrier Engineering in a Thin-Film Intermediate-Band Solar Cell”, IEEE Journal of Photovoltaics 5, 878 (2015); DOI: 10.1109/JPHOTOV.2015.2412451
  • A. Datas, E. López, I. Ramiro, E. Antolín, A. Martí, A. Luque, R. Tamaki, Y. Shoji, T. Sogabe, and Y. Okada, “Intermediate band solar cell with extreme broadband spectrum quantum efficiency”, Physical Review Letters 114, 157701 (2015);http://dx.doi.org/10.1103/PhysRevLett.114.157701
  • R. Tamaki, Y. Shoji, S. Naitoh, Y. Okada, and K. Miyano, “Extreme broadband photocurrent spectroscopy on InAs quantum dot solar cells”, Proceedings of SPIE 9358, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV, 93580V (2015); DOI: 10.1117/12.2081084
  • Daniel J Farrell, Hassanet Sodabanlu, Yunpeng Wang, Masakazu Sugiyama, and Yoshitaka Okada, “Can a Hot-Carrier Solar Cell also be an Efficient Up-converter?”, IEEE Journal of Photovoltaics 5, 571 (2015); DOI: 10.1109/JPHOTOV.2014.2373817
  • Ryo Tamaki, Yasushi Shoji, Yoshitaka Okada, and Kenjiro Miyano, “Spectrally resolved interband and intraband transitions by two-step photon absorption in InGaAs/GaAs quantum dot solar cells”, IEEE Journal of Photovoltaics 5, 229 (2015); DOI: 10.1109/JPHOTOV.2014.2368712
  • Pierre Rale, Amaury Delamarre, Gilbert El-Hajje, Ryo Tamaki, Kentaroh Watanabe, Yasushi Shoji, Yoshitaka Okada, Masakazu Sugiyama, Laurent Lombez, and Jean-François Guillemoles, “Quantitative optical measurement of chemical potentials in intermediate band solar cells”, Journal of Photonics for Energy 5, 053092 (2015); DOI: 10.1117/1.JPE.5.053092
  • P. G. Linares, E. López, I. Ramiro, A. Datas, E. Antolín, Y. Shoji, T. Sogabe, Y. Okada, A. Martí, and A. Luque, “Voltage limitation analysis in strain-balanced InAs/GaAsN quantum dot solar cells applied to the intermediate band concept”, Solar Energy Materials & Solar Cells 132, 178 (2015); http://dx.doi.org/10.1016/j.solmat.2014.08.041
  • B. Behaghel, R. Tamaki, N. Vandamme, K. Watanabe, C. Dupuis, N. Bardou, H. Sodabanlu, A. Cattoni, Y. Okada, M. Sugiyama, S. Collin, and J.-F. Guillemoles, “Absorption enhancement through Fabry-Pérot resonant modes in a 430 nm thick InGaAs/GaAsP multiple quantum wells solar cell”, Applied Physics Letters 106, 081107 (2015); http://dx.doi.org/10.1063/1.491346
  • Stanko Tomić, Tomah Sogabe, and Yoshitaka Okada, “In-plane coupling effect on absorption coefficients of InAs/GaAs quantum dots arrays for intermediate band solar cell”, Progress in Photovoltaics: Research and Applications 23, 546 (2015); doi 10.1002/pip.2455
  • Tomah Sogabe, Akio Ogura, Mitsuyoshi Ohba, and Yoshitaka Okada, “Self-consistent electrical parameter extraction from bias dependent spectral response measurements of III-V multi-junction solar cells”, Progress in Photovoltaics: Research and Applications 23, 37 (2015); doi: 10.1002/pip.2392
  • Shunya Naitoh and Yoshitaka Okada, “Efficiency Estimations for Multijunction and Intermediate Band Solar Cells Using Actual Measured Solar Spectra in Japan”, Journal of Solar Energy Engineering 137, 034504 (2015); doi: 10.1115/1.4029382
  • Tomah Sogabe, Yasushi Shoji, Mitsuyoshi Ohba, Naito Shunya, Naoya Miyashita, Chao-Yu Hung, Akio Ogura, and Yoshitaka Okada, “Fabrication and Characterization of GaAs Tunnel Diode and ErAs Nanoparticles Enhanced GaAs Tunnel Diode for Multijunction Solar Cell”, Materials Research Society Symposium Proceedings 1602 (2014); DOI: 10.1557/opl.2014.4
  • M. M. Islam, N. Miyashita, N. Ahsan, T. Sakurai, K. Akimoto, and Y. Okada, “Effect of antimony on the deep-level traps in GaInNAsSb thin films”, Applied Physics Letters 105, 112103 (2014); http://dx.doi.org/10.1063/1.4895940.
  • Efrain E. Tamayo R., K. Watanabe, R. Tamaki, T. Hoshii, M. Sugiyama, Y. Okada, K. Miyano, A. Cvetkovic, R. Mohedano, and M. Hernandez, “Plasma etching antireflection nanostructures on optical elements in concentrator photovoltaic systems”, Journal of Photonics for Energy, 5, 057006 (2014); doi:10.1117/1.JPE.5.057006.
  • Shuhei Yagi, Shunsuke Noguchi, Yasuto Hijikata, Shigeyuki Kuboya, Kentaro Onabe, Yoshitaka Okada, and Hiroyuki Yaguchi, “Enhanced optical absorption due to E+-related band transition in GaAs:N δ-doped superlattices”, Applied Physics Express 7, 102301 (2014); http://dx.doi.org/10.7567/APEX.7.102301
  • Ryo Tamaki, Yasushi Shoji, Yoshitaka Okada, and Kenjiro Miyano, “Spectrally resolved intraband transitions on two-step photon absorption in InGaAs/GaAs quantum dot solar cell”, Applied Physics Letters 105, 073118 (2014); http://dx.doi.org/10.1063/1.4893879
  • Tomah Sogabe, Yasushi Shoji, Peter Mulder, John Schermer, Efrain Tamayo, and Yoshitaka Okada, “Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study”, Applied Physics Letters 105, 113904 (2014); http://dx.doi.org/10.1063/1.4896114
  • Tomah Sogabe, Yasushi Shoji, Mitsuyoshi Ohba, Katsuhisa Yoshida, Ryo Tamaki, Hwen-Fen Hong, Chih-Hung Wu, Cherng-Tsong Kuo, Stanko Tomić, and Yoshitaka Okada, “Intermediate-band dynamics of quantum dots solar cell in concentrator photovoltaic modules”, Scientific Reports (Nature Publishing Group), 4, 2014/4/25. doi:10.1038/srep04792 (OPEN ACCESS)
  • Akio Ogura, Tomah Sogabe, Mitsuyoshi Ohba, and Yoshitaka Okada, “Extraction of electrical parameters in multi-junction solar cells from voltage dependent spectral response without light bias”, Japanese Journal of Applied Physics 53, 066601 (2014); doi:10.7567/JJAP.53.066601
  • Yukiko Kamikawa-Shimizu, Robert Patterson, Alexander Milekhin, Kouichi Akahane, Yasushi Shoji, Dietrich R.T. Zahn, Yoshitaka Okada, and Gavin Conibeer, “Study of phonons in self-assembled InAs quantum dots embedded in an InGaAlAs matrix”, Physica E 57, 1 (2014. doi: 10.1016/j.physe.2013.10.023
  • Tomah Sogabe, Akio Ogura, Yoshitaka Okada, “Analysis of bias voltage dependent spectral response in Ga0.51In0.49P/Ga0.99In0.01As/Ge triple junction solar cell”, Journal of Applied Physics 115, 7, 074503 (2014)
  • Tomah Sogabe, Toshiyuki Kaizu, Yoshitaka Okada, and Stanko Tomić, “Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell”, Journal of Renewable Sustainable Energy, 6, 011206 (2014); doi: 10.1063/1.4828359
  • Tomah Sogabe, Akio Ogura, Chao-Yu Hung, Valery Evstropov, Mikhali Mintairov, Maxim Shvarts, and Yoshitaka Okada, “Experimental characterization and self-consistent modeling of luminescence coupling effect in III-V multijunction solar cells”, Applied Physics Letters 103, 263907 (2013) http://dx.doi.org/10.1063/1.4858970
  • Y. Tamura, T. Kaizu, T. Kiba, M. Igarashi, R. Tsukamoto, A. Higo, W. Hu, C. Thomas, M. Erman Fauzi, T. Hoshii, I. Yamashita, Y. Okada, A. Murayama, and S. Samukawa, “Quantum size effects in GaAs nanodisks fabricated using a combination of the bio-template technique and neutral beam etching”, Nanotechnology 24, 285301 (2013).
  • Naoya Miyashita, Nazmul Ahsan, Muhammad Monirul Islam, and Yoshitaka Okada, “Composition control of quinary GaInNAsSb alloy grown by molecular beam epitaxy”, Physica Status Solidi C, 10, 1369 (2013); DOI 10.1002/pssc.201300283
  • F. K. Tutu, J. Wu, P. Lam, M. Tang, N. Miyashita, Y. Okada, J. Wilson, R. Allison, and H. Liu, “Antimony mediated growth of high-density InAs quantum dots for photovoltaic cells”, Applied Physics Letters, 103, 043901 (2013); http://dx.doi.org/10.1063/1.4816503
  • Yoshitaka Okada, Katsuhisa Yoshida, Yasushi Shoji, Tomah Sogabe, “Recent progress on quantum dot intermediate band solar cells”, IEICE Electronics Express, 10, 1 (2013); DOI: 10.1587/elex.10.20132007
  • N. Ahsan, N. Miyashita, M. M. Islam, K. M. Yu, W. Walukiewicz, and Y. Okada, “Effect of Sb on GaNAs Intermediate Band Solar Cells”, IEEE Journal of Photovoltaics, 3, 730 (2013): DOI 10.1109/JPHOTOV.2012.2228296
  • F. K. Tutu, P. Lam, J. Wu, N. Miyashita, Y. Okada, K-H. Lee, N. J. Ekins-Daukes, J. Wilson, and H. Liu, “InAs/GaAs quantum dot solar cell with an AlAs cap layer”, Applied Physics Letters, 102, 163907 (2013): DOI: 10.1063/1.4803459
  • Muhammad Monirul Islam, Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Defect study of molecular beam epitaxy grown undoped GaInNAsSb thin film using junction-capacitance spectroscopy”, Applied Physics Letters 102, 074104 (2013); http://dx.doi.org/10.1063/1.4793430
  • Muhammad Monirul Islam, Naoya Miyashita, Nazmul Ahsan, Takeaki Sakurai, Katsuhiro Akimoto, and Yoshitaka Okada, “Photocapacitance study of MBE grown GaInNAsSb thin film solar cells”, Journal of Crystal Growth 378, 57 (2013). http://dx.doi.org/10.1016/j.jcrysgro.2012.12.150
  • Yasushi Shoji, Katsuhiro Akimoto, and Yoshitaka Okada, “(INVITED PAPER) Self-organized InGaAs/GaAs quantum dot arrays for use in high-efficiency intermediate-band solar cells”, Journal of Physics D: Applied Physics 46, 024002 (2013); doi:10.1088/0022-3727/46/2/024002
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Effect of antimony on uniform incorporation of nitrogen atoms in GaInNAs films for solar cell application”, Solar Energy Materials and Solar Cells, 111, 127–132 (2013); http://dx.doi.org/10.1016/j.solmat.2012.12.036
  • Yoshitaka Okada, Katsuhisa Yoshida, Yasushi Shoji, Akio Ogura, Pablo Garcia-Linares, Antonio Marti, and Antonio Luque, “The effect of concentration on the performance of quantum dot intermediate-band solar cells”, AIP Conference Proceedings 1477, pp. 10-13 (2012); doi:http://dx.doi.org/10.1063/1.4753822
  • 岡田 至崇，「量子ドット太陽電池の現状と将来展望」，Journal of Vacuum Society of Japan, 55, 556 (2012)
  • Daisuke Sato, Junya Ota, Kazutaka Nishikawa, Yasuhiko Takeda, Naoya Miyashita, and Yoshitaka Okada, “Extremely long carrier lifetime at intermediate states in wall-inserted type II quantum dot absorbers”, Journal of Applied Physics, 112, 094305 (2012); http://dx.doi.org/10.1063/1.4764030
  • Muhammad Monirul Islam, Naoya Miyashita, Nazmul Ahsan, Takeaki Sakurai, Katsuhiro Akimoto, and Yoshitaka Okada, “Identification of defect types in moderately Si-doped GaInNAsSb layer in p- GaAs/n- GaInNAsSb/n-GaAs solar cell structure using admittance spectroscopy”, Journal of Applied Physics 112, 114910 (2012); http://dx.doi.org/10.1063/1.4768716
  • Naoya Miyashita, Nazmul Ahsan, Makoto Inagaki, Muhammad Monirul Islam, Masafumi Yamaguchi, and Yoshitaka Okada, “High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy”, Applied Physics Letters 101, 222112 (2012); http://dx.doi.org/10.1063/1.4768949
  • Katsuhisa Yoshida, Yoshitaka Okada and Nobuyuki Sano, “Device simulation of intermediate band solar cells: Effects of doping and concentration”, Journal of Applied Physics 112, 0814510 (2012); http://link.aip.org/link/japiau/v112/i8/p084510/s1
  • Yasushi Shoji, Katsuhiro Akimoto, and Yoshitaka Okada, “Optical properties of multi-stacked InGaAs/GaNAs quantum dot solar cell fabricated on GaAs (311)B substrate”, Journal of Applied Physics 112, 064314 (2012); http://dx.doi.org/10.1063/1.4752733
  • Toshiyuki Kaizu, Yosuke Tamura, Makoto Igarashi, Weiguo Hu, Rikako Tsukamoto, Ichiro Yamashita, Seiji Samukawa, and Yoshitaka Okada, “Photoluminescence from GaAs nanodisks fabricated by using combination of neutral beam etching and atomic hydrogen-assisted molecular beam epitaxy regrowth”, Applied Physics Letters 101, 113108 (2012); http://dx.doi.org/10.1063/1.4752233
  • Nazmul Ahsan, Naoya Miyashita, Muhammad Monirul Islam, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “Two-photon excitation in an intermediate band solar cell structure”, Applied Physics Letters 100 (2012) 172111; http://dx.doi.org/10.1063/1.4709405
  • Yoshitaka Okada, “High-efficiency Quantum Nanostructure Solar Cells: Present and Future Opportunities (Special article)”, Journal of the Japan Institute of Energy 91 (2012) 382
  • Yasushi Shoji, Kohei Narahara, Hideharu Tanaka, Takashi Kita, Katsuhiro Akimoto, and Yoshitaka Okada, “Effect of spacer layer thickness on multi-stacked InGaAs quantum dots grown on GaAs (311)B substrate for application to intermediate band solar cells” Journal of Applied Physics, 111, 074305 (2012)
  • Kazutaka Nishikawa, Yasuhiko Takeda, Tomoyoshi Motohiro, Daisuke Sato, Junya Ota, Naoya Miyashita, and Yoshitaka Okada, “Extremely long carrier lifetime over 200 ns in GaAs wall-inserted type II InAs quantum dots” Applied Physics Letters, 100, 113105 (2012)
  • Kazutaka Nishikawa, Yasuhiko Takeda, Ken-ichi Yamanaka, Tomoyoshi Motohiro, Daisuke Sato, Junya Ota, Naoya Miyashita, and Yoshitaka Okada, “Over 100 ns intrinsic radiative recombination lifetime in type-II InAs/GaAs1－xSbx quantum dots” Journal of Applied Physics, 111, 044325 (2012)
  • Mohd Fairuz Budiman, Weiguo Hu, Makoto Igarashi, Rikako Tsukamoto, Taiga Isoda, Kohei M Itoh, Ichiro Yamashita, Akihiro Murayama, Yoshitaka Okada and Seiji Samukawa, “Control of optical bandgap energy and optical absorption coefficient by geometric parameters in sub-10 nm silicon-nanodisc array structure” Nanotechnology, 23, 065302 (2012)
  • Kouichi Akahane, Naokatsu Yamamoto, Tetsuya Kawanishi, Sergio Bietti, Ayami Takata, and Yoshitaka Okada, “Stacking-layer-number dependence of highly stacked InAs quantum dot laser diodes fabricated using strain-compensation technique” Proceedings of SPIE, 8277, 827703 (2012)
  • C-H. Huang, X-Y. Wang, M. Igarashi, A. Murayama, Y. Okada, I. Yamashita, and S. Samukawa “Optical absorption characteristic of highly ordered and dense two-dimensional array of silicon nanodisks” Nanotechnology, 22 (2011) 105301
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji, Kouichi Akahane, and Yoshitaka Okada “Evaluation of multi-stacked InAs/GaNAs self-assembled quantum dots on GaAs (001) grown using different As species” Journal of Crystal Growth 324 (2011) 158
  • Ayami Takata, Kouichi Akahane, Naoki Yamamoto, and Yoshitaka Okada “Optical gain of multi-stacked InAs quantum dots grown on InP (311)B substrate by strain-compensation technique” physica status solidi (c) 8 (2011) 254
  • Ryuji Oshima, Yoshitaka Okada, Ayami Takata, Shuhei Yagi, Kouichi Akahane, Ryo Tamaki, and Kenjiro Miyano “High-density quantum dot superlattice for application to high-efficiency solar cells” physica status solidi (c) 8 (2011) 619
  • Takayuki Morioka and Yoshitaka Okada “Dark current characteristics of InAs/GaNAs strain-compensated quantum dot solar cells” Physica E 44 (2011) 390
  • R. Oshima, J. Y. Huang, N. Miyashita, K. Matsubara, Y. Okada, and F. A. Ponce “Transmission electron microscopy study of GaInNAs(Sb) thin films grown by atomic hydrogen-assisted molecular beam epitaxy” Applied Physics Letters 99 (2011) 191907
  • Yoshitaka Okada, Takayuki Morioka, Katsuhisa Yoshida, Ryuji Oshima, Yasushi Shoji, Tomoya Inoue, and Takashi Kita “Increase in photocurrent by optical transitions via intermediate quantum states in direct-doped InAs/GaNAs strain-compensated quantum dot solar cell” Journal of Applied Physics 109 (2011) 024301
  • Katsuhisa Yoshida, Yoshitaka Okada, and Nobuyuki Sano “Self-consistent simulation of intermediate band solar cells: Effect of occupation rates on device characteristics” Applied Physics Letters. 97 (2010) 133503
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji, Kouichi Akahane, and Yoshitaka Okada “Growth of multi-stacked InAs/GaNAs quantum dots grown with As2 source in atomic hydrogen-assisted molecular beam epitaxy” Physica E, 42 (2010) 2745
  • Ryuji Oshima, Ayami Takata, Yasushi Shoji, Kouichi Akahane, and Yoshitaka Okada “InAs/GaNAs starain-compensated quantum dots stacked up to 50 layers for use in high-efficiency solar cell” Physica E, 42 (2010) 2757
  • Yasushi Shoji, Ryuji Oshima, and Ayami Takata, and Yoshitaka Okada “The effect of spacer layer thickness on vertical alignment of InGaAs/GaNAs quantum dots grown on GaAs(311)B substrate” Physica E, 42 (2010) 2768
  • Yasushi Shoji, Ryuji Oshima, Ayami Takata, and Yoshitaka Okada “Structural properties of multi-stacked self-organized InGaAs quantum dots grown on GaAs (3 1 1)B substrate” Journal of Crystal Growth, 312 (2010) 226
  • Yoshitaka Okada, Ryuji Oshima, and Ayami Takata “Characteristics of InAs/GaNAs strain-compensated quantum dot solar cell” Journal of Applied Physics 106 (2009) 024306
  • Naoya Miyashita, Shuhei Ichikawa, Yoshitaka Okada “Improvement of GaInNAsSb films fabricated by atomic hydrogen-assisted molecular beam epitaxy” Journal of Crystal Growth, 311 (2009) 3249
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji, and Yoshitaka Okada “Optical studies on InAs/InGaAs/GaNAs strain-compensated quantum dots grown on GaAs (001) by molecular beam epitaxy” Journal of Crystal Growth, 311 (2009) 1774
  • Ryuji Oshima, Yasushi Shoji, Ayami Takata, and Yoshitaka Okada “Growth of InGaAs/GaNAs strain-compensated quantum dot superlattice on GaAs (311)B by molecular beam epitaxy” Journal of Crystal Growth, 311 (2009) 1770
  • Ryuji Oshima, Ayami Takata, Yasushi Shoji and Yoshitaka Okada “The effect of pacer layer thickness on the properties of quantum dot solar cells” Proceedings of 18th International Photovoltaic Science and Engineering Conference, 6-3o-016, Kolkata, India (2009)
  • Yasushi Shoji, Ryuji Oshima, Ayami Takatai, and Yoshitaka Okada “Fabrication of InGaAs/GaNAs strain-compensated quantum dot solar cell on GaAs (311)B substrate” Proceedings of 18th International Photovoltaic Science and Engineering Conference, 6-3p-023, Kolkata, India (2009)
  • Naoya Miyashita, Shuhei Ichikawa, and Yoshitaka Okada“Characteristics of GaInNAsSb Solar Cells Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy” Proceedings of 18th International Photovoltaic Science and Engineering Conference, 5-1o-014, Kolkata, India (2009)
  • Ryuji Oshima, Ayami Takata, and Yoshitaka Okada “Strain-compensated InAs/GaNAs quantum dots for use in high-efficiency solar cells”Applied Physics Letters 93 (2008) 083111
  • Ayami Takata, Ryuji Oshima, Hidemi Shigekawa, and Yoshitaka Okada “Growth of GaNAs films with As2 source in atomic hydrogen-assisted molcular beam epitaxy” Journal of Crystal Growth, 310 (2008) 2234
  • Ryuji Oshima, Yuta Nakamura, Ayami Takata, and Yoshitaka Okada “Optical properties of multi-stacked InAs/GaNAs strain-compensated quantum dots” Journal of Crystal Growth, 310 (2008) 3710
  • Naoya Miyashita, Yukiko Shimizu, and Yoshitaka Okada “Carrier mobility characteristics in GaInNAs dilute nitride films grown by atomic hydrogen-assisted molecular beam epitaxy”, Journal of Applied Physics, 102, 044904 (2007)
  • Yukiko Shimizu, Naoya Miyashita, Yusuke Mura, Akira Uedono, and Yoshitaka Okada “Effect of growth temperature on the properties of Ga(In)NAs thin films by atomic hydrogen-assisted RF-MBE”, Journal of Crystal Growth, 301-302, 579 (2007)
  • Ryuji Oshima, Ayami Takata, and Yoshitaka Okada “Increased photoabsorption in strain-compensated quantum dot solar cells” Proceedings of 17th International Photovoltaic Science and Engineering Conference, 925 (2007)
  • Ryuji Oshima, Yuta Nakamura, Ayami Takata, and Yoshitaka Okada “Multi-stacked InAs/GaNAs strain-compensated quantum dot solar cells” Proceedings of 22nd European Photovoltaic Solar Energy Conference, 60 (2007)
  • Ryuji Oshima, Kouichi Akahane, Masahiro Tsuchiya, Hidemi Shigekawa, and Yoshitaka Okada “Optical properties of stacked InAs self-organized quantum dots on InP(311)B” The 37th International Symposium on Compound Semiconductors, Kagawa (2010)
  • Ryuji Oshima, Takayuki Hashimoto, Hidemi Shigekawa, and Yoshitaka Okada “InAs self-assembled quantum dots superlattice structure fabricated by strain compensation technique” AIP conference proceedings, 893 (2007) 811

Conferences

  • Yoshitaka Okada, Tomah Sogabe, Chao-Yu Hung, Ryo Tamaki, “Demonstration of Energy-Transfer Ratchet Intermediate-Band Solar Cells Using Erbium-Doped GaAs”
    The 22nd International Vacuum Congress (IVC-22), Sapporo (Sept. 2022).
  • Myeongok Kim, Nazmul Ahsan, Chen Chen, Dorota A. Kowalczyk, Nicholas Trainor, Joan M. Redwing, Yoshitaka Okada, “Effect of Off-angle on the Epitaxial Growth of MoS2 on Off-angle Sapphire by Metal-organic Chemical Vapor Deposition”
    9th International Symposium on Control of Semiconductor Interfaces (ISCSI-IX), Nagoya (Sept. 2022).

  • M. Giteau, Y. Okada et al, “(Invited) Enabling hot-carrier solar cells by combining ultrathin quantum absorbers with light trapping”, SPIE Photonics West 2022, San Francisco, USA (Feb. 2022).
  • Y. Oteki, Maxime Giteau, Kei Fukushima, Kento Kitahara, Naoya Miyashita, Ryo Tamaki, and Yoshitaka Okada, “Optimizing the positions of quantum dot layers to increase the light absorption in quantum dot solar cells with light trapping structure”, 6th IEEE Electron Devices Technology and Manufacturing (EDTM) Conference, Virtual (March 2022).
  • M. Giteau, C. Drommi, F. Challet, H. Sodabanlu, H. Esmaielpour, M. Bescond, D. Suchet, S. Collin, J-F. Guillemoles, and Y. Okada, “Understanding the cooling mechanisms of hot carriers in ultrathin GaAs layers”, SPIE Photonics West 2021, San Francisco, USA (March 2021).
  • Y. Oteki, M. Giteau, K. Fukushima, K. Kitahara, N. Miyashita, R. Tamaki, and Y. Okada, “Optimizing the Position of Quantum Dot Layers to Increase Absorption: Towards High-Efficiency Quantum Dot Solar Cells”, International Conference on Nano-photonics and Nano-optoelectronics 2021, Virtual (April 2021).
  • Y. Okada, “(Invited) Approaches to high-efficiency intermediate band photovoltaics”, European MRS Spring 2021, Virtual (May 2021).
  • R. Tamaki, Y. Shoji, L. Lombez, J.-F. Guillemoles and Y. Okada, “Quasi-Fermi level splitting in InAs quantum dot solar cells from photoluminescence measurements”, SPIE Photonics West 2020, San Francisco, USA (Feb. 2020).
  • Bernice Mae F. Yu Jeco, Achilles E. Espaldon, Tomoyasu Sado, Kentaroh Watanabe, Kumiko Oguma, Yoshitaka Okada, ”Design of concentrator multijunction solar modules for UV-LED disinfection of water in off-the-grid areas”, 47th IEEE Photovoltaic Specialists Conference (PVSC) Virtual (June 2020).
  • M. Giteau, J.-F. Guillemoles, K. Watanabe, N. Miyashita, H. Sodabanlu, A. Delamarre, R. Tamaki, Z. Jehl, D. Suchet, S. Collin, J. Goffard, A. Cattoni, L. Lombez, M. Sugiyama, and Y. Okada, “Light absorption enhancement in ultra-thin layers for hot carrier solar cells”, SPIE Photonics West 2019, San Francisco, USA (Feb. 2019).
  • Y. Okada, “Epitaxial Lift-Off III-V solar cells”, University of Cambridge & The University of Tokyo, Round-Table Workshop on Future Quantum Photovoltaics, Cambridge, UK (Mar. 2019).
  • Y. Okada, “(Invited) Optimizing the structure of quantum dot intermediate-band solar cells”, 30th World Nano Conference, Zürich, Switzerland (May 2019).
  • Y. Oteki, Y. Shoji, N. Miyashita, Y. He, and Y. Okada, “GaSb/GaAs quantum nanostructures for intermediate band solar cell under high sunlight concentration”, Compound Semiconductor Week 2019 (CSW), Nara (May 2019).
  • M. Giteau, K. Watanabe, N. Miyashita, H. Sodabanlu, S. Collin, J.-F. Guillemoles, and Y. Okada, “Maximizing the Electron Temperature in Hot-Carrier Solar Cells”, 21st International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON), Nara (July 2019).
  • N. Miyashita, Y. He, N. Ahsan, and Y. Okada, “Effect of Annealing on the Bottom Cell in GaInP/GaAs/GaInNAsSb Triple Junction Solar Cells by MBE/MOCVD Hybrid Growth”, Compound Semiconductor Week 2019 (CSW), Nara (May 2019).
  • Y. Okada, “(Invited) Quantum Dot Photovoltaics: Challenges Towards 50% Efficiency”, 10th International Conference on Materials for Advanced Technologies (ICMAT), Marina Bay Sands, Singapore (June 2019).
  • T. Nakamura, M. Imaizumi, H. Akiyama, and Y. Okada, “Effect of SRH recombination rate coefficient on internal luminescence efficiency and conversion efficiency of space solar cells”, 46th IEEE Photovoltaic Specialists Conference (PVSC), Chicago, USA (June 2019).
  • B.M. Yu Jeco, A. Chikhalkar, M. Giteau, R. Tamaki, N. Ahsan, R. King, and Y. Okada, “The influence of Al2O3 passivation of III-V on Ge multijunction solar cells to the spatial distribution of luminescent coupling effect”, 46th IEEE Photovoltaic Specialists Conference (PVSC), Chicago, USA (June 2019).
  • N. Miyashita, N. Ahsan, Y. Okada, R. Tatavarti, A. Wibowo, and N. Pan, “Epitaxial Lifted-off Thin Film GaInP/GaAs/GaInNAsSb Lattice-Matched Triple Junction Solar Cells”, 46th IEEE Photovoltaic Specialists Conference (PVSC), Chicago, USA (June 2019).
  • Y. Okada, N. Miyashita, Y. Oteki, and Y. Shoji, “High-Efficiency InAs-InGaAs Quantum Dash Solar Cells Developed Through Current Constraint Engineering”, 46th IEEE Photovoltaic Specialists Conference (PVSC), Chicago, USA (June 2019).
  • Y. Okada, “(Plenary) Quantum Dot Intermediate Band Photovoltaics: Steps Towards Higher Efficiency”, 6th International Conference on Nanotechnology, Nanomaterials & Thin Films for Energy Applications (NANOENERGY), Kuala Lumpur, Malaysia (July 2019).
  • Y. Oteki, Y. Shoji, N. Miyashita, and Y. Okada, “Effect of Ga deposition rate on GaAsSb/GaAs Quantum Dots formation”, Asia Pacific Society for Materials Research 2019 Annual Meeting, Sapporo (July 2019).
  • M. Giteau, K. Watanabe, N. Miyashita, H. Sodabanlu, S. Collin, J.-F. Guillemoles, and Y. Okada, “Maximizing the Electron Temperature in Hot-Carrier Solar Cells”, 21st International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON), Nara (July 2019).
  • Y. Okada, “(Invited) Progress and Approaches to High-Efficiency Intermediate Band Photovoltaics Progress and Approaches to High-Efficiency Intermediate Band Photovoltaic”, 7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano), Kobe (Sept. 2019).
  • Y. Oteki, N. Miyashita, Y. Shoji, Y. Okada, “Energy Levels of Type-II GaAsSb/GaAs Quantum Dots for Intermediate Band Solar Cell”, 7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano), Kobe (Sept. 2019).
  • N. Miyashita, and Y. Okada, “Strain Compensated Dilute Nitride MQWs as New 1 eV Solar Cell Absorber”, 7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano), Kobe (Sept. 2019).
  • R. Tamaki, Y. Shoji, and Y. Okada, “Low Temperature Absolute Photoluminescence Spectroscopy on InAs Quantum Dot Solar Cells”, 7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano), Kobe (Sept. 2019).
  • Naoya Miyashita, Yilun He, Nazmul Ahsan, Yoshitaka Okada, “Effect of Annealing on The Bottom Cell in GaInP/GaAs/GaInNAsSb Triple Junction Solar Cells by MBE/MOCVD Hybrid Growth”, 2019 Compound Semiconductor Week (CSW), Nara (May 2019).
  • R. Tamaki, Y. Shoji, L. Lombez, J.-F. Guillemoles, and Y. Okada, “Quantitative analysis of InAs quantum dot solar cells by photoluminescence spectroscopy”, SPIE Photonics West 2018, San Francisco (Feb. 2018).
  • H. O Xu, A. Delamarre, J. Jia, B.M. Yu Jeco, K. Watanabe, Y. Okada, J.-F. Guillemoles, Y. Nakano, and M. Sugiyama,” Transport Efficiency Imaging in Multi-junction Solar Cells by Luminescence Analysis”, 7th World Conference on Photovoltaic Energy Conversion (WCPEC), Hawaii, USA (June 2018).
  • M. Asami, K. Toprasertpong, K. Watanabe, Y. Nakano, Y. Okada, and M. Sugiyama, “Comparison of Effective Carrier Mobility between Wire on Well and Multiple Quantum Well by Time of Flight Measurement”, 7th World Conference on Photovoltaic Energy Conversion (WCPEC), Hawaii, USA (June 2018).
  • Y. Okada, “(Invited) Quantum Dot Intermediate Band Solar Cells: Steps toward High Efficiency”, Kobe University Smart Materials Seminar, Kobe (Nov. 2018).
  • Maxime Giteau, Stéphane Collin, Zacharie Jehl, Daniel Suchet, Jean-François Guillemoles, and Yoshitaka Okada, “Advanced Light Trapping for Hot-Carrier Solar Cells”, 7th World Conference on Photovoltaic Energy Conversion (WCPEC), Hawaii, USA (June 2018).
  • Zacharie Jehl, Daniel Suchet, Naoya Miyashita, Benoit Behagel, Maxime Giteau, Amaury Delamarre, Bernice Mae F. Yu Jeco, Jean-Francois Guillemoles, and Yoshitaka Okada, “Hot Carrier Extraction Using Energy Selective Contacts and Feedback on the Remaining Distribution”, 7th World Conference on Photovoltaic Energy Conversion (WCPEC), Hawaii, USA (June 2018).
  • Ryo Tamaki, Yasushi Shoji, and Yoshitaka Okada, “Efficient Two-Step Photon Absorption in Type-II GaSb Quantum Dot Solar Cells”, Light, Energy and the Environment 2017, Boulder, USA (Nov. 2017).
  • Ayaka Matsuoka, Yasushi Shoji, Ryo Tamaki, and Yoshitaka Okada,“InGaAs/AlGaAs Quantum Dot Intermediate Band Solar Cells Fabricated on GaAs (311)B Substrate”, Light, Energy and the Environment 2017, Boulder, USA (Nov. 2017).
  • B. M. F. Yu Jeco, K. Yoshida, R. Tamaki, N. Ahsan, and Y. Okada, “Analysis of Current Generation in InGaP/GaAs/Ge Triple Junction Solar Cells with Optically Non-Uniform Luminescence Coupling Effect”, 33rd European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Amsterdam, The Netherlands (Sept. 2017).
  • Y. Shoji, K. Watanabe, A. Ogura, and Y. Okada, “50-layer stacked InGaAs/GaAs quantum dot solar cell with light scattering structure”, 33rd European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Amsterdam, The Netherlands (Sept. 2017).
  • Nazmul Ahsan et al., “(Invited) Characterization of Cr-doped CuGaS2 thin films for intermediate band solar cell application”, International Symposium for Advanced Materials Research (ISAMR-2017), Sun Moon Lake, Taiwan (Aug. 2017).
  • Ryo Tamaki, “(Invited) Full spectrum quantum efficiency on III-V quantum dot solar cells”, International Workshop on Advanced Smart Materials and Engineering for Nano-and Bio-Technologies, Kobe, Japan (July 2017).
  • S. Naito, K. Yoshida, R. Tamaki, N. Miyashita, and Y. Okada, “High-Efficiency Quantum Dot Intermediate Band Solar Cell (IBSC): Effect of Carrier Occupancy Rations in IB”, International Research Conference on Sustainable Energy, Engineering, Materials and Environment (SEEME)), Newcastle upon Tyne, UK (July 2017).
  • Tomah Sogabe, Kohdai Nii, Katsuyoshi Sakamoto, Koichi Yamaguchi, and Yoshitaka Okada, “Hot Carrier Transportation Dynamics in InAs/GaAs Quantum Dot Solar Cell”, 44th IEEE Photovoltaic Specialists Conference, Washington DC, USA (June 2017).
  • Ryo Tamaki, Yasushi Shoji, and Yoshitaka Okada, “Type-II Quantum Dots for Application to Photon Ratchet Intermediate Band Solar Cells”, 44th IEEE Photovoltaic Specialists Conference, Washington DC, USA (June 2017).
  • Nazmul Ahsan, Sivaperuman Kalainathan, Naoya Miyashita, Takuya Hoshii, and Yoshitaka Okada, “Multiband Formation in Cr doped CuGaS2 Thin Films Synthesized by Chemical Spray Pyrolysis”, 44th IEEE Photovoltaic Specialists Conference, Washington DC, USA (June 2017).
  • Yoshitaka Okada, Yasushi Shoji, Chao-Yu Hung, Daniel J. Farrell, and Tomah Sogabe, “High Density Quantum Dot Solar Cells for Concentrating Photovoltaics (CPV)”, 17th International Conference on Environment and Electrical Engineering, Milano, Italy (May 2017).
  • Ryo Kato, Shuhei Yagi, Hiroyuki Yaguchi, and Yoshitaka Okada, “Electrical characterization of n-type GaAs:N δ-doped superlattices”, Compound Semiconductor Week 2017 (CSW 2017), Berlin, Germany (May 2017).
  • Naoya Miyashita, “Effect of Hydrogen Annealing for Dilute Nitride GaInNAsSb Solar Cells”, Compound Semiconductor Week 2017 (CSW 2017), Berlin, Germany (May 2017).
  • Yasushi Shoji and Yoshitaka Okada, “Effect of thin InAlAs buffer layer on InAs/InGaAs quantum dots grown on InP (311)B substrate”, Compound Semiconductor Week 2017 (CSW 2017), Berlin, Germany (May 2017).
  • Ryo Tamaki, “Hybrid Photovoltaic and Thermoelectric Module for High Concentration Solar System”, 13th International Conference on Concentrator Photovoltaic Systems (CPV-13), Ottawa, Canada (May 2017).
  • Yoshitaka Okada, Yasushi Shoji, and Ryo Tamaki, “(Invited) Challenges and Progress on the Development of Quantum Dot Intermediate Band Solar Cells”, 2017 MRS Spring Meeting, Phoenix, USA (Apr. 2017).
  • Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “(Invited) III-V Dilute Nitrides for Intermediate Band Solar Cell”, Global Photovoltaic Conference (GPVC) 2017, Gwangju, Korea (Mar. 2017).
  • Shunya Naito, Ryo Tamaki, Naoya Miyashita, Katsuhisa Yoshida, and Yoshitaka Okada, “Two-step photon absorption in intermediate band solar cells controlled by the electron filling ratio of quantum dots”, ISPlasma 2017, Aichi, Japan (Mar. 2017).
  • Zacharie Jehl, Daniel Suchet, Anatole Julian, Cyril Bernard, Naoya Miyashita, Francois Gibelli, Yoshitaka Okada, and Jean-Francois Guillemoles, “Modeling and characterization of double resonant tunneling diodes for application as energy selective contacts in hot carrier solar cells”, SPIE Photonics West 2017, San Francisco, USA (Jan. 2017).
  • Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “Multiband modification of III-V dilute nitrides for IBSC application”, SPIE Photonics West 2017, San Francisco, USA (Jan. 2017).
  • Naoya Miyashita, “(Invited) Characterization Of Dilute Nitride Based Photovoltaics for Multi-junction Solar cell Applications”, 3rd International Conference on Mechanics and Mechatronics Research (ICMMR 2016), Uthangarai, India (Dec. 2016).
  • Nazmul Ahsan, Naoya Miyashita, Takuya Hoshii, Kalainathan Sivaperuman, and Yoshitaka Okada, “(Invited) Emerging semiconductors for highly efficient PV Applications”, 3rd International Conference on Mechanics and Mechatronics Research (ICMMR 2016), Uthangarai, India (Dec. 2016).
  • Naoya Miyashita, “(Invited) Improvement Of Dilute Nitride GaInNAsSb Thin Films And Photovoltaic Characteristics”, International Conference on Materials Processing and Applications (ICMPA2016), Vellore, India (Dec. 2016).
  • Nazmul Ahsan, Naoya Miyashita, Takuya Hoshii, Kalainathan Sivaperuman, and Yoshitaka Okada, “(Invited) Multiband semiconductors for next generation PV applications”, International Conference on Materials Processing and Applications (ICMPA2016), Vellore, India (Dec. 2016).
  • Bernice Mae Yu Jeco, “Acquisition and Analysis of Electrocardiogram Waveforms with Diagnosis Transmission through Short Message Service Communication System”, IEEE TENCON 2016, Singapore (Nov. 2016).
  • Shuhei Yagi, Yoshitaka Okada et al., “Effect of Carrier Blocking Layer on Carrier Collection in Inter-mediate-Band Solar Cells using GaAs:N Delta-Doped Superlattice”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Warakorn Yanwachirakul, Naoya Miyashita, Hassanet Sodabanlu, Kasidit Toprasertpong, Kentaroh Watanabe, Sugiyama Masakazu, Yoshitaka Okada, and Yoshiaki Nakano, “Design Structure of Free-barrier InGaAs/GaNAs Multiple Quantum Well Solar Cells with 1.2 eV Energy Gap”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Bernice Mae Yu Jeco, “Spatial Distribution of Temperature Dependent luminescence coupling Current in InGaP/GaAs/Ge Triple Junction Solar Cells”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Yasushi Shoji, “Multi-stacked GaSb/GaAs type-II quantum nanostructure for application to intermediate band solar cells”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Zacharie Jehl, “Selective contacts for Hot Carrier Solar Cells using asymmetric double resonant tunnelling barriers”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Katsuhisa Yoshida, “Simulation Analysis of Impurity-Band assisted Quantum-Dot Intermediate-Band Solar Cells”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Naoya Miyashita, Benoît Behaghel, Jean-François Guillemoles, and Yoshitaka Okada, “Enhancement of Photocurrent in Epitaxial Lift-Off Thin Film GaInNAsSb Solar Cells by The Light Confinement Structure”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Yoshitaka Okada, “(Invited) Progress of Quantum Dot Intermediate-Band Solar Cells”, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore (Oct. 2016).
  • Tomah Sogabe, Yoshitaka Okada, and Koichi Yamaguchi, “Investigation of Hot Carrier Transportation Dynamics in InAs/GaAs Quantum Dot Solar Cell”, High-efficiency material for Photovoltaics (HEMP 2016) workshop, London, UK (Sept. 2016).
  • Yoshitaka Okada, “High-Efficiency Quantum Dot Intermediate Band Solar Cells”, 5th International Conference & Exhibition on Clean Energy, Montreal, Canada (Aug. 2016).
  • H. Suzuki, P. Yuan, X. Meng, Y. Saito, K. Sasaki, R. Tamaki, H. Tatsuoka, N. Ahsan, and Y. Okada, “Synthesis of Flower-like Si Nanostructures on Si Substrates”, APAC-SILICIDE 2016, Fukuoka, Japan (July 2016).
  • Yoshitaka Okada, “Improvements in Quantum Dot Intermediate Band Solar Cells”, 19th International Conference of Superlattices, Nanostructures and Nanodevices, Hong Kong (July 2016).
  • Yasushi Shoji, Nazmul Ahsan, Ryo Tamaki, and Yoshitaka Okada,“InAs/InAlAsSb quantum nanostructures grown on InP substrate for intermediate band solar cell application”, Compound Semiconductor Week 2016 (CSW), Toyama, Japan (June 2016).
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Improvement of 1.0 eV GaInNAsSb solar cell performance upon annealing”, Compound Semiconductor Week 2016 (CSW), Toyama, Japan (June 2016).
  • Yoshitaka Okada, “(Invited) Current Trends in High-Efficiency III-V Nanostructured Solar Cells”, Compound Semiconductor Week 2016 (CSW), Toyama, Japan (June 2016).
  • Naoya Miyashita, “(Invited) Enhancement of carrier collection in GaInNAs:Sb solar cells”, EMN Prague Meeting, Energy Materials Nanotechnology, Prague, Czech Republic (June 2016).
  • Bernice Mae Yu Jeco, Tomah Sogabe, Akio Ogura, Naoya Miyashita, Ryo Tamaki, and Yoshitaka Okada, “Laser Beam Induced Current (LBIC) Mapping of InGaP/GaAs/Ge Triple Junction Solar Cells with Luminescence Coupling”, 43rd IEEE Photovoltaic Specialists Conference, Portland, USA (June 2016).
  • Ryo Tamaki, Yasushi Shoji, Takeyoshi Sugaya, and Yoshitaka Okada,“Universal Linear Relationship on Two-Step Photon Absorption Processes in In(Ga)As Quantum Dot Solar Cells”, 43rd IEEE Photovoltaic Specialists Conference, Portland, USA (June 2016).
  • Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “Designing III-V dilute nitride alloys for IBSC application”, 43rd IEEE Photovoltaic Specialists Conference, Portland, USA (June 2016).
  • Akio Ogura, Yoshitaka Okada, and Tomah Sogabe, “Analysis of Multijunction Solar Cells Under High Concentrations”, 12th International Conference on Concentrator Photovoltaic System, Freiburg, Germany (Apr. 2016).
  • Akio Ogura, Mizuki Mori, Katsuhisa Yoshida, Tomah Sogabe, and Yoshitaka Okada, “Device simulation of thin-film intermediate-band solar cell using drift-diffusion model and FDTD method (oral)”, SPIE Photonics West OPTO 2016 San Francisco, USA (Feb. 2016).
  • Ryo Tamaki, Yasushi Shoji, and Yoshitaka Okada, “Design optimization for two-step photon absorption in quantum dots by infrared photocurrent spectroscopy (oral)”, SPIE Photonics West OPTO 2016, San Francisco, USA (Feb. 2016).
  • Nazmul Ahsan, “(invited) Characterization of transision metal-doped chalcopyrite thin films for photovoltaic application”, EMN meeting on Photovoltaics, Hong Kong (Jan. 2016).
  • Yoshitaka Okada, “(invited) Challenges and Advances in Quantum Dot Intermediate Band Solar Cells”, 2015 MRS Fall Meeting , Hynes　Convention　Center, Boston(Nov. 2015).
  • Tomah Sogabe, “Fingerprint of Kondo Resonance in Co-TPP Molecule Coupled to CuN Atomic Layer: A Combined LT-STS and DFT-NEGF Study (oral)”, Collaboration seminer of Univ. of Tokyo and Univ. of Cambridege, Cambridege (Nov. 2015).
  • Ryo Tamaki, “Photocarrier Kinetics in Quantum Dot Superlattice (oral)”, Collaboration seminer of Univ. of Tokyo and Univ. of Cambridege, Cambridege (Nov. 2015).
  • Yoshitaka Okada, “Quantum Dot Growth Technology by MBE for Advanced Photovoltaics (oral)”, Collaboration seminer of Univ. of Tokyo and Univ. of Cambridege, Cambridege (Nov. 2015).
  • Shuhei Yagi, Yosuke Sato, Nozomu Ueyama, Tomoya Suzuki, Kazuki Osada, Yoshitaka Okada, and Hiroyuki Yaguchi, “(Invited) Optical and Structural Characterization of GaAs:N δ-Doped Superlattices Grown by Molecular Beam Epitaxy (poster)”, SemiconNano2015, Taiwan (Sept. 2015).
  • Chao-Yu Hung, Tomah Sogabe, Ryo Tamaki, Naoya Miyashita, and Yoshitaka Okada, “Light absorption via discrete states in GaAs solar cell embedded with Er complex (poster)”, SemiconNano2015, Taiwan (Sept. 2015).
  • Katsuhisa Yoshida, Yoshitaka Okada, Nobuyuki Sano, “Effect of Sequential Tunnelling on Quantum-Dot Intermediate-band Solar Cells (poster)”, SemiconNano2015, Taiwan (Sept. 2015).
  • R. Tamaki, Y. Shoji, K. Miyano and Y. Okada, “Effect of external biases on infrared photo-response in InAs/AlGaAs quantum dot solar cell (poster)”, SemiconNano2015, Taiwan (Sept. 2015).
  • Tomah Sogabe, Akio Ogura, Yoshitaka Okada, Qing Shen, Yuki Kuga, Taro Toyoda, Stanko Tomi?, Paul D. McNaughter, and Paul O’Brien (poster), “Experimental analysis of hot state multiple exciton generation in PbSe quantum dots and its transportation modelling”, SemiconNano2015, Taiwan (Sept. 2015).
  • Nazmul Ahsan, “(Invited) Keynote Speech (Emerging semiconductor materials and nanostructures for high efficiency intermediate band solar cells）”, 3rd International Conference on Green Energy and Technology, Dhaka, Bangladesh (Sept. 2015).
  • T. Hoshii, S. Naitoh and Y. Okada, “Photo-Assisted Impedance Spectroscopy for Quantum Dot Solar Cells”, 3rd International Conference on Green Energy and Technology, Dhaka, Bangladesh (Sept. 2015).
  • Katsuhisa Yoshida, “(Invited) Sequential Tunneling Effect on Quantum-Dot Intermediate-Band Solar Cells”, 18th International Workshop on Computational Electronics, West Lafayette, Indiana USA (Sept. 2015).
  • A. Julian, Z Jehl, Y. Okada and J.F. Guillemoles, “Modeling of Selective Energy Contacts for Hot Carrier Solar Cells (poster)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC) Hamburg (Sept. 2015).
  • S. Naitoh, N. Miyashita, K. Toprasertpong, R. Tamaki, T. Hoshii, M. Sugiyama, and Y. Okada, “Effect of Si Doping on Performance of Quantum Dot Solar Cells (poster)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Hamburg (Sept. 2015).
  • P. Rale, B. Behaghel, A. Delamarre, N. Vandamme, D. Ory, S. Collin, L. Lombez, J.F. Guillemoles, R. Tamaki, Y. Shoji, and Y. Okada, “Quantitative Optical Spectroscopy of QDs Intermediate Band Solar Cells (oral)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Hamburg (Sept. 2015).
  • N. Miyashita, N. Ahsan, and Y. Okada, “Evaluation of 1.0 eV GaInNAsSb Solar Cells for Multi-Junction Applications and Annealing Effects (poster)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Hamburg (Sept. 2015).
  • D. Yamashita, G. Kono, T. Hoshii, K. Watanabe, M. Sugiyama, T. Suga, Y. Okada, and Y. Nakano, “The Effect of Fast-Atom-Beam Ion Species in the Surface Activated Bonding Process for Multi-Junction Solar Cells (oral)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Hamburg (Sept. 2015).
  • A. Datas, A.B. Cristobal, G. Sala, I. Anton Hernandez, J.C. Minano, P. Benitez, C. Algora, A.W. Bett, D. Lackner, M. Niemeyer, S.P. Philipps, G. Siefer, N.J. Ekins-Daukes, F. Roca, C. Cancro, I. Luque-Heredia, W. Warmuth, M. Baudrit, Y. Okada, M. Sugiyama, Y. Hishikawa, T. Takamoto, K. Araki, A. Fukuyama, K. Nishioka, H. Suzuki, N. Kuze, Y. Moriyasu, T. Kita, A. Kotagiri, N. Kojima, A. Marti Vega, M. Yamaguchi, and A. Luque, “NGCPV: a New Generation of Concentrator Photovoltaic Cells, Modules and Systems (a Final Review) (plenary)”, The 31st European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Hamburg (Sept. 2015).
  • Mizuki Mori, Akio Ogura, Katsuhisa Yoshida, Tomah Sogabe, Yoshitaka Okada, “Device simulation of thin film solar cell characteristics considering Fabry-Perot cavity effect”, International Nano-Optoelectronics Workshop, Tokyo (Aug. 2015).
  • Tomoyuki Kada, Taizo Tanibuchi, Shigeo Asahi, Toshiyuki Kaizu, Yukihiro Harada, Takashi Kita, Ryo Tamaki, Yoshitaka Okada, and Kenjiro Miyano, “Two-Step Photocarrier Generation in InAs/GaAs Quantum DotSuperlattice Intermediate Band Solar Cell”, The 42nd IEEE Photovoltaic Specialists Conference (PVSC), New Orleans (June 2015).
  • Ryo Tamaki, Yasushi Shoji, Shunya Naitoh, Yoshitaka Okada, and Kenjiro Miyano, “Extreme broadband photocurrent spectroscopy on InAs quantum dot solar cells”, SPIE Photonics West, San Francisco (Feb. 2015).
  • Yoshitaka Okada (INVITED), “Self-organized QDs for intermediate-band solar cells”, 2014 Workshop on High-efficiency material for photovoltaics (HEMP), Imperial College London (July, 2014).
  • Yoshitaka Okada (INVITED), “Recent Progress on Quantum Dot Intermediate Band Solar Cells”, The 27th International Microprocesses and Nanotechnology Conference (MNC), Fukuoka (Nov. 2014).
  • Yoshitaka Okada (INVITED), “Quantum Dot Superlattice for High-efficiency Intermediate Band Solar Cells”, OSA Congress on Optical Nanostructures and Advanced Materials for Photovoltaics (PV), Canberra (Dec. 2014).
  • Jean-Francois Guillemoles, Laurent Lombez, Amaury Delamarre, Gilbert El-Hajje,Pierre Rale, Kentaroh Watanabe, Masakazu Sugiyama, Yoshitaka Okada, Ryo Tamaki, and Yasushi Shoji, “Imaging quasi fermi level splitting in intermediate-band solar cells”, SPIE Photonics West, San Francisco (February 2014).
  • N. Miyashita, N. Ahsan, and Y. Okada, “Improved Carrier Collection in Thick GaInNAsSb Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • N. Miyashita, N. Ahsan, and Y. Okada, “Evaluation of Concentrator Photovoltaic Properties of GaInNAsSb Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • Y. Shoji, R. Tamaki, A. Datas, A. Marti, A. Luque, and Y. Okada, “Effect of Field Damping Layer on Two Step Absorption of Quantum Dots Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014). Best Poster Award受賞！
  • R. Tamaki, Y. Shoji, Y. Okada, and K. Miyano, “Photofilling Effect on Optical Transitions in InGaAs/GaAs Quantum Dot Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • T. Sogabe, Y. Shoji, C-Y. Hung, D. J. Farrell, and Y. Okada, “InAs/GaAs Quantum Dot Solar Cell with 26.8% Efficiency Achieved Through Current Constraint Engineering”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • A. Ogura, T. Sogabe, and Y. Okada, “Evaluation of Conversion Efficiency for Multijunction Solar Cell with Luminescent Coupling Considering Series and Shunt Resistance Effects”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • C-Y. Hung, T. Sogabe, N. Miyashita, S. Naitoh, and Y. Okada, “Fabrication of Hybrid ErAs:InAs Quantum Dots for Solar Cell Application”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • S. Tomic´, T. Sogabe, and Y. Okada, “Theory of Quantum Coupling and Efficiency in QD Array Based Intermediate Band Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • K. Yoshida, Y. Okada, and N. Sano, “Effect of Sequential Tunneling in Quantum Dot Intermediate Band Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • Behaghel, P. Rale, Y. Shoji, R. Tamaki, N.Vandamme, L. Lombez, C. Dupuis, A. Cattoni, K. Watanabe, H. Sodabanlu, M. Sugiyama, Y. Okada, S. Collin, and J-F. Guillemoles, “Strong Absorption Exaltation in Ultrathin QDs and MQWs for Tandem and Intermediate Band Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • T. Thomas, M. Fuhrer, D. Alonso Alvarez, N. J. Ekins-Daukes, D. Lackner, P. Kailuweit, S. P. Philipps, A. W. Bett, M. Sugiyama, and Y. Okada, “Potential for Reaching 50% Power Conversion Efficiency Using Quantum Heterostructures”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014). Best Paper Award受賞！
  • D. Lackner, S. P. Philipps, F. Dimroth, H. Sodabanlu, K. Watanabe, N. Miyashita, M. Sugiyama, Y. Okada, and A. W. Bett, “Monolithically Integrated Multi-Junction Cells builtby Multiple Separate Growths in Different Epitaxy Reactors”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • E. E. Tamayo R., K. Watanabe, T. Hoshii, R. Tamaki, M. Sugiyama, Y. Shoji, Y. Okada, and K. Miyano, “Maskless Broadband Antireflection Technology on Glass for Flat and Concentrator PV”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • T. Kada, S. Asahi, T. Kaizu, T. Kita, R. Tamaki, Y. Okada, and K. Miyano, “Efficient Two-step Photon Absorption in InAs/GaAs Quantum Dot Solar Cells”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • T. Suzuki, K. Osada, S. Yagi, S. Naito, Y. Hijikata, Y. Okada, and H. Yaguchi, “Molecular Beam Epitaxy Growth of Intermediate Band Materials Based on GaAs:N δ-Doped Superlattices”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014). Young Researcher Award受賞！
  • K. Osada, T, Suzuki, S. Yagi, S. Naito, Y. Shoji, Y. Okada, Y. Hijikata, and H. Yaguchi, “Control of Intermediate Band Configuration in GaAs:N δ-doped Superlattice”, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto (Nov. 2014).
  • N. Ahsan, N. Miyashita, K. M. Yu, W. Walukiewicz, and Y. Okada, “Improving the Multiband Character of GaAs-based Dilute Nitrides”, 18th International Conference on Molecular Beam Epitaxy, Flagstaff, Arizona (September, 2014)
  • Daniel J Farrell, Hassanet Sodabanlu, Yunpeng Wang, Masakazu Sugiyama, and Yoshitaka Okada, “Can a hot-carrier solar cell also be an efficient up-converter?”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Yasushi Shoji and Yoshitaka Okada, “Effect of External Bias on Multi-stacked InAs/AlGaAs Quantum Dots Solar Cell”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Tomah Sogabe, Yasushi Shoji, Peter Mulder, John Schermer, Efrain Tamayo, and Yoshitaka Okada, “Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Akio Ogura, Tomah Sogabe, Daniel J Farrell, and Yoshitaka Okada, “Analysis of GaAs/AlGaAs quantum nanodisk solar cell with intermediate band carrier transportation”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Ryo Tamaki, Yasushi Shoji, Yoshitaka Okada, and Kenjiro Miyano, “Spectrally resolved interband and intraband transitions by two-step photon absorption in InGaAs/GaAs quantum dot solar cells”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Benoit Behaghel, Ryo Tamaki, Nicolas Vandamme, Kentaroh Watanabe, Christophe Dupuis, Nathalie Bardou, Hassanet Sodabanlu, Andrea Cattoni, Yoshitaka Okada, Masakazu Sugiyama, Stephane Collin, and Jean-Francois Guillemoles, “Four-fold MQWs Absorption Enhancement in a 430 nm Thick InGaAs/GaAsP MQWs Solar Cell”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Chao-Yu Hung, Tomah Sogabe, Naoya Miyashita, Yasushi Shoji, Shunya Naito, and Yoshitaka Okada, “Local conductivity characteristics of individual ErAs nanoparticle for solar cell tunnel junction application”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada, “Concentrating Photovoltaic Properties of GaInNAsSb/Ge Dual Junction Tandem Solar Cell”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, “Electron barrier engineering in a thin-film intermediate band solar cell”, The 40th IEEE Photovoltaic Specialists Conference, Denver (June 2014).
  • T. Sogabe, V. Evstropov, C. Hung, M. Mintairov, A. Ogura, Y. Okada, and M. Shvarts, “Self-consistent Modeling and Bias Dependent Spectral Response Measurement of Luminescence Coupling Effect in Concentrator III-V Multijunction Solar Cells”, 10th International Conference on Concentrator Photovoltaic Systems (CPV-10),, Albuquerque (April 2014), Tue-D-13.
  • A. Ogura, C. Hung, M. Ohba, T. Sogabe, and Y. Okada, “Characterization of Triple-Junction Tandem Solar Cells with Voltage Dependent Spectral Response (SR-V) without Light Bias”, 10th International Conference on Concentrator Photovoltaic Systems (CPV-10),, Albuquerque (April 2014), Wed-D-18.
  • Yoshitaka Okada, Yasushi Shoji, Ryo Tamaki, and Tomah Sogabe, “Operation Characteristics of InAs Quantum Dot Intermediate-Band Solar Cells”, MRS Fall Meeting, Boston (Nov. 2013).
  • Yoshitaka Okada (INVITED), “Recent Progress and Future Prospect of Quantum Dot Intermediate-Band Solar Cells”, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), Taipei (October 2013).
  • Tomah Sogabe, “Self-consistent Approach for Modeling the Luminescent Coupling in Concentrator III-V Multijunction Solar Cells”, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), Taipei (October 2013).
  • Akio Ogura, Tomah Sogabe, Y. Saito, A. Kotagiri, and Y. Okada, “Electrical Parameters Extraction from Voltage Dependent Spectral Response in Multi-junction Solar Cells without Bias Light”, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), Taipei (Oct. 2013).
  • Shuhei Yagi, Shunsuke Noguchi, Yasuto Hijikata, Hiroyuki Yaguchi, Shigeyuki Kuboya, Kentaro Onabe, and Yoshitaka Okada, “Fabrication and Characterization of Intermediate Band Solar Cells Using GaAs:N Delta-Doped Superlattice”, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), Taipei (October 2013).
  • Yoshitaka Okada, Katsuhisa Yoshida, Yasushi Shoji and Tomah Sogabe (INVITED), “Operation Characteristics of Quantum Dot Intermediate-Band Solar Cells”, 2013 JSAP-MRS Joint Symposia, Kyoto (Sept. 2013).
  • E. E. Tamayo Ruiz, R. Tamaki, K. Watanabe, M. Sugiyama, Y. Shoji, D. J. Farrell, Y. Okada, and K. Miyano, “Antireflection Structures on Fresnel Lenses Fabricated by Induced Coupled Plasma Etching for Improving CPV Systems”, The 28th European Photovoltaic Solar Energy Conference and Exhibition (EU-PVSEC), Paris (Sept. 2013).
  • Yoshitaka Okada, Katsuhisa Yoshida, YasushiShoji and Tomah Sogabe, “Operation Characteristics of Quantum Dot Intermediate-Band Solar Cells under Sunlight Concentration”, The 55th Electronic Materials Conference (EMC), Univ. Notre Dame (June 2013).
  • Yasushi Shoji and Yoshitaka Okada, “InGaAs Quantum Dot Solar Cells With High Energy Gap Matrix Layers”, The 39th IEEE Photovoltaic Specialists Conference, Tampa (June 2013).
  • Stanko Tomic, Tomah Sogabe, and Yoshitaka Okada, “In-Plane Coupling Effect In Inas/Gaas Quantum Dots Arrays For Intermediate Band Solar Cell”, The 39th IEEE Photovoltaic Specialists Conference (PVSC), Tampa (June 2013).
  • Efrain E. Tamayo R., Kentaroh Watanabe, Masakazu Sugiyama, Yasushi Shoji, Yoshitaka Okada, and Kenjiro Miyano, “Fabrication of broadband antireflection structures on glass substrates by Reactive Ion Etching for application on homogenizers in CPV systems”, The 39th IEEE Photovoltaic Specialists Conference (PVSC) , Tampa (June 2013). ポスター賞受賞！
  • Naoya Miyashita, Muhammad Monirul Islam, Nazmul Ahsan, and Yoshitaka Okada, “Device Structure Engineering of GaInNAsSb/GaAs Hetero-junction Solar Cells”, The 39th IEEE Photovoltaic Specialists Conference (PVSC), Tampa (June 2013).
  • Shuhei Yagi, Shunsuke Noguchi, Yasuto Hijikata, Shigeyuki Kuboya, Kentaro Onabe, Yoshitaka Okada, and Hiroyuki Yaguchi, “Optical Absorption by E + Miniband of GaAs:N Delta-Doped Superlattices”, The 39th IEEE Photovoltaic Specialists Conference (PVSC), Tampa (June 2013).
  • N. Miyashita, Y. Okada, and K. Watanabe, “Photovoltaic Characteristics of GaInNAsSb Solar Cells under Concentrated Light Source”, 9th Conference on Concentrator Photovoltaics (CPV-9), Miyazaki (April, 2013)
  • S. Naito and Y. Okada, “Power Generation of Series and Series/Parallel Triple Tandem Solar Cells Derived from Measured Spectra in Japan”, 9th Conference on Concentrator Photovoltaics (CPV-9), Miyazaki (April, 2013)
  • A. Ogura, T. Sogabe, M. Ohba, and Y. Okada, “Self-consistent Fitting of Electrical Parameters for InGaAs/Ge Dual Junction Solar Cells from Bias-dependent Spectral Response”, 9th Conference on Concentrator Photovoltaics (CPV-9), Miyazaki (April, 2013)
  • T. Sogabe, Y. Shoji1, M. Ohba , H-F. Hong, C-H. Wu, C-T. Kuo, and Y. Okada, “First Demonstration of InAs/GaAs Quantum Dot CPV Module”, 9th Conference on Concentrator Photovoltaics (CPV-9), Miyazaki (April, 2013)
  • F. K. Tutu, P. Lam, J. Wu, N. Miyashita, Y. Okada, K-H. Lee, N. J. Ekins-Daukes,J. Wilson, and H. Liu, “Influence of a thin AlAs cap layer on the performance of InAs/GaAs quantum dot solar cells”, Semiconductor and Integrated OptoElectronics Conference, Cardiff (April, 2013)
  • N. Ahsan, “Photoluminescence in GaNAs(Sb) thin films and carrier localization”, 2012 Collaborative Conference on Crystal Growth (3CG), Orlando (December, 2012)
  • Naoya Miyashita (Invited), “Fabrication of nip and pin structure GaInNAsSb solar cells”, 2012 Collaborative Conference on Crystal Growth (3CG), Orlando (December, 2012)
  • Stanko Tomic, Tomah Sogabe, and Yoshitaka Okada, “Modelling of Vertical and In-plane Quantum Dots Arrays for High Efficiency Solar Cells”, 2012 MRS Fall Meeting, Boston (Nov. 2012), E8.04.
  • Kazutaka Nishikawa, Yasuhiko Takeda, Ken-ichi Yamanaka, Tomoyoshi Motohiro, Daisuke Sato, Junya Ota, Naoya Miyashita, and Yoshitaka Okada, “Long Carrier Lifetime at Intermediate States over 200ns Using InAs/GaAsSb Type II Quantum Dots”, 2012 MRS Fall Meeting, Boston (Nov. 2012), E10.03.
  • (Invited) Katsuhisa Yoshida and Yoshitaka Okada, “Device simulation of intermediate band solar cells”, 12th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD’12), Shanghai (Aug. 2012).
  • Nazmul Ahsan, Naoya Miyashita, Muhammad Monirul Islam and Yoshitaka Okada, “Effect of Sb on the optical properties of MBE-grown GaNAs films”, The 17th International Conference on Molecular Beam Epitaxy, Nara (Sept. 2012).
  • Toshiyuki Kaizu, Yosuke Tamura, Makoto Igarashi, Weiguo Hu, Seiji Samukawa and Yoshitaka Okada, “Observation of photoluminescence from 2-dimentional GaAs nanodisk array regrown by atomic hydrogen-assisted molecular beam epitaxy”, The 17th International Conference on Molecular Beam Epitaxy, Nara (Sept. 2012).
  • Naoya Miyashita, Nazmul Ahsan, Makoto Inagaki, Muhammad Monirul Islam, Masafumi Yamaguchi and Yoshitaka Okada, “High electron mobility in Ga(In)NAs films grown by MBE”, The 17th International Conference on Molecular Beam Epitaxy, Nara (Sept. 2012).
  • Muhammad Monirul Islam, Naoya Miyashita, Nazmul Ahsan, Takeaki Sakurai, Katsuhiro Akimoto and Yoshitaka Okada, “Photocapacitance study of MBE grown GaInNAsSb thin film solar cell”, The 17th International Conference on Molecular Beam Epitaxy, Nara (Sept. 2012).
  • Yasushi Shoji, Katsuhiro Akimoto and Yoshitaka Okada, “InAs quantum dots grown on GaAsSb layer on different substrate orientation”, The 17th International Conference on Molecular Beam Epitaxy, Nara (Sept. 2012).
  • Yoshitaka Okada (Invited), “InAs Quantum Dots-Based Intermediate Band Solar Cells”, 2nd Workshop on High-efficiency material for photovoltaics, Imperial College London (2012).
  • Y. Okada (Invited), “High-Efficiency Quantum Dot Intermediate-Band Solar Cells”, IUMRS International Conference on Electronic Materials (IUMRS-ICEM2012) , Yokohama (Sept. 2012).
  • Y. Okada (Invited), “Intermediate-band photovoltaics based on quantum dot superlattice”, 2012 International Conference on Superlattices, Nanostructures, and Nanodevices, Dresden (July 2012).
  • Efrain Eduardo Tamayo Ruiz, Kentaroh Watanabe, Ryosuke Watanabe, Masakazu Sugiyama, Yoshitaka Okada, Kenjiro Miyano, “Efficiency Simulations of Top Surface Light Management Structures for Concentrator Solar Cells Using RCWA and Detailed Balance Theory”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012).
  • M. M. Islam, N. Miyashita, N. Ahsan, and Y. Okada, “Bias-Dependent Admittance Measurement of GaInNAsSb-Based Solar Cell Structure”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012).
  • N. Miyashita, N. Ahsan, M. M. Islam, and Y. Okada, “Study on the Device Structure of GaInNAs(Sb)-Based Solar Cells for Use in 4-Junction Tandem Solar Cells”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012).
  • N. Ahsan, N. Miyashita, M.M. Islam, K.M. Yu, and W. Walukiewicz, and Y. Okada, “Two-Photon Excitation in a Dilute Nitride Intermediate-Band Solar Cell”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012).
  • K. Yoshida, N. Sano, and Y. Okada, “Device Simulation of Intermediate-Band Solar Cells: Dependence on Number of Intermediate-Band Layers”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012).
  • Y. Shoji, K. Akimoto, and Y. Okada, “InGaAs/GaAsSb Type-II Quantum Dots for Intermediate-Band Solar Cell”, The 38th IEEE Photovoltaic Specialists Conference, Austin (June 2012)
  • Y. Okada, P. García-Linares, A. Luque, A. Martí, A. Ogura, Y. Shoji, and K. Yoshida, “Effect of Concentration on the Performance of Quantum Dot Intermediate-Band Solar Cells”, 8th International Conference on Concentrating Photovoltaic Systems, Toledo (April 2012)
  • Yoshitaka Okada (Invited), “Growth and application of three-dimensional quantum dot superlattice for high-efficiency intermediate band solar cells”, International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano 2011), Traunkirchen (Sept. 2011)
  • Yoshitaka Okada (Invited), “High efficiency quantum dot intermediate band solar cells”, 6th International Symposium on Surface Science, Tokyo (Dec. 2011)
  • Mohammad Monirul Islam, Naoya Miyashita, Nazmul Ahsan, and Yoshitaka Okada “ELECTRICAL CHARACTERIZATION OF GaInNAsSb THIN FILM” The 21th International Photovoltaic Science and Engineering Conference, Fukuoka (2011)
  • Yasushi Shoji, Kohei Narahara, H. Tanaka, Takashi Kita, Katsuhiro Akimoto, and Yoshitaka Okada “EFFECT OF SPACER LAYER THICKNESS ON MULTI-STACK InGaAs QUANTUM DOTS GROWN ON GaAs (311)B SUBSTRATE FOR USE IN INTERMEDIATE BAND SOLAR CELLS” The 21th International Photovoltaic Science and Engineering Conference, Fukuoka (2011)
  • Nazmul Ahsan, Naoya Miyashita, Tooru Tanaka, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada “INHOMOGENEITY IN THE PHOTOREFLECTANCE OF GANAS GROWN BY ATOMIC H-ASSISTED MBE” The 21th International Photovoltaic Science and Engineering Conference, Fukuoka (2011)
  • Yoshitaka Okada “Self-organized heteroepitaxy of InAs quantum dots and application to intermediate band solar cells” Workshop on High-efficiency material for photovoltaics, Imperial College London (2011)
  • Markus F Führer, Jessica GJ Adams, Keith WJ Barnham, Ben C Browne, Ngai LA Chan, Daniel J Farrell, Louise Hirst, Kan-Hua Lee, Ned J Ekins-Daukes, Akio Ogura, Katsuhisa Yoshida, Yoshitaka Okada “EXTENSIBLE MODELLING FRAMEWORK FOR NANOSTRUCTURED III-V SOLAR CELLS” The 37th IEEE Photovoltaic Specialists Conference, Seattle (2011)
  • X-Y. Wang, C-H. Huang, R. Tsukamoto, T. Kaizu, M. Igarashi, P-A. Mortemousque, H. Shinohara, Y. Okada, A. Murayama, K. Itoh, Y. Ohno, Y. Ichiro, and S. Samukawa “Damage-free Top-down Processes of Fabricating Two-dimensional Array of Sub-10nm Nanometer GaAs Nanodisks using Bio-template and Neutral Beam Etching for Intermediate Band Solar Cell Applications” The 37th IEEE Photovoltaic Specialists Conference, 759 (Seattle, 2011)
  • M. Igarashi, C-H. Huang, X-Y. Wang, M. F. Budiman, Y. Tamura, T. Kiba, A. Murayama, T. Kaizu, Y. Okada, and S. Samukawa “Optical Absorption, Photo-Luminescence and Miniband Formation of a Highly Ordered and Dense 2-Dimensional Array of Si Nanodisks for quantum Dot Solar Cells” The 37th IEEE Photovoltaic Specialists Conference, 992 (Seattle, 2011)
  • Takayuki Morioka, Yasushi Shoji, and Yoshitaka Okada “Current Enhancement in Direct Si-Doped InAs/GaNAs Strain-Compensated Quantum Dot Solar Cells” The 37th IEEE Photovoltaic Specialists Conference, Seattle (2011)
  • A. Ogura, T. Morioka, P. Garcia-Linares, E. Hernandez, I. Ramiro, I. Artacho, E. Antolin, A. Marti, A. Luque, M. Yamaguchi, and Y. Okada “Modeling of Quantum Dot Solar Cells for Concentrator PV Applications” The 37th IEEE Photovoltaic Specialists Conference, Seattle (2011)
  • Katsuhisa Yoshida, Yoshitaka Okada, and Nobuyuki Sano “Effects of Absorption Spectra Overlapping on Structure Design of Intermediate Band Solar Cells” The 37th IEEE Photovoltaic Specialists Conference, Seattle (2011)
  • Naoya Miyashita, Nazmul Ahsan, M. Monirul Islam, Yoshitaka Okada “Evaluation of GalnNAs(Sb) Solar Cells for Use in Next Generation lll-V Tandem Solar Cells” The 37th IEEE Photovoltaic Specialists Conference, Seattle (2011)
  • Akio Ogura, Takayuki Morioka, and Yoshitaka Okada “Modeling of GaAs p-i-n solar cells on dark and concentration characteristics by using a modified equivalent circuit” 7th International Conference on Concentrating Photovoltaic Systems (CPV-7), Las Vegas (2011)
  • Naoya Miyashita, Nazmul Ahsan, Kin M. Yu, Wladek Walukiewicz and Yoshitaka Okada “Antimony Surfactant Mediated Improvement of the Properties of GaInNAsSb Films for Multi-junction Tandem Solar Cells” Materials research society 2011 spring meeting, Sanfrancisco (2011), B7.3
  • Nazmul Ahsan, Naoya Miyashita, Tooru Tanaka, Kin M. Yu, Wladek Walukiewicz and Yoshitaka Okada “Photo-modulated Reflectance of GaNAs Grown by Atomic Hydrogen-assisted MBE” Materials research society 2011 spring meeting, Sanfrancisco (2011), B7.8
  • Muhammad M. Islam, Naoya Miyashita, Nazmul Ahsan, Takeaki Sakurai, Katsuhiro Akimoto and Yoshitaka Okada“Admittance Spectroscopy Study of MBE Grown Undoped-GaInNAsSb Thin Film for Multi-junction Tandem Solar Cell”Materials research society 2011 spring meeting, Sanfrancisco (2011), B7.20
  • Yasushi Shoji, Takayuki Morioka, Katsuhiro Akimoto and Yoshitaka Okada “Multi-stacked InGaAs/GaNAs Self-organized Quantum Dot Arrays for Use in Intermediate Band Solar Cells” Materials research society 2011 spring meeting, Sanfrancisco (2011), B5.56
  • C-H. Huang, M. Igarashi, M. F. Budiman, R. Oshima, I. Yamashita, Y. Okada, and S. Samukawa “Optical Characteristics of Two-dimensional Array of Si Nano-disks Fabricated by Defect-free Neutral Beam Etching with Bio-template” 2010 International Conference on Solid State Devices and Materials, L-3-5 (Tokyo, 2010)
  • Yoshitaka Okada (Invited) “Quantum Dot Superlattice for High Efficiency Intermediate Band Solar Cells” 2010 International Conference on Solid State Devices & Materials, Tokyo (2010)
  • Yoshitaka Okada (Invited) “Quantum Dot Superlattice Intermediate Band Solar Cell; Proving the Concept and Beyond” Workshop on Information, Nano and Photonics Technology 2010 (Kobe)
  • Katsuhisa Yoshida, Yoshitaka Okada, and Nobuyuki Sano “Numerical analysis of intermediate band (IB) solar cells: effect of absorption coefficients and doping of IB state” Workshop on Information, Nano and Photonics Technology 2010 (Kobe)
  • Takayuki Morioka, Ryuji Oshima, Yasushi Shoji, Tomoya Inoue, Takashi Kita, and Yoshitaka Okada “Multi-stacked InAs/GaNAs quantum dots with direct Si doping for use in intermediate band solar cell” Workshop on Information, Nano and Photonics Technology 2010 (Kobe)
  • Ayami Takata, Kouichi Akahane, Naokatsu Yamamoto and Yoshitaka Okada “Optical gain of multi-stacked InAs quantum dots grown on InP(311)B substrate by strain-compensation technique” The 16th International Conference on Molecular Beam Epitaxy, Berlin (2010)
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji, Kouichi Akahane, and Yoshitaka Okada “Evaluation of multi-stacked InAs/GaNAs self-assembled quantum dots on GaAs (001) grown using different As species” The 37th International Symposium on Compound Semiconductors, Kagawa (2010)
  • Katsuhisa Yoshida, Yoshitaka Okada, Nobuyuki Sano “Self-Consistent Drift-Diffusion Approach for Analysis Intermediate Band Solar Cells with Multi-Stacked Quantum Dots ” 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, Valencia (2010)
  • Naoya Miyashita, Haruhiro Oigawa, Yoshitaka Okada “Effect of Antimony on Electron Trap Density in GaInNAsSb Solar Cell Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy ” 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, Valencia (2010)
  • Katsuhisa Yoshida, Yoshitaka Okada, Nobuyuki Sano “Self-consistent drift-diffusion analysis of intermediate band solar cell (IBSC) : Effect of energetic position of IB on conversion efficiency” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010)
  • Naoya Miyashita, Nazmul Ahsan, Yoshitaka Okada “Antimony enhanced homogeneous nitrogen incorporation into GaInNAs films grown by atomic hydrogen-assisted molecular beam epitaxy” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010)
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji, Koichi Akahane, Yoshitaka Okada “Fabrication of 100 layer-stacked InAs/GaNAs strain-compensated quantum dots on GaAs(001) for application to intermediate band solar cell” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010)
  • Yasushi Shoji, Ryuji Oshima, Ayami Takata, Takayuki Morioka, Yoshitaka Okada “Multi-staqcked InGaAs/GaNAs quantum dot solar cell fabricated on GaAs (311)B substrate” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010) (Poster Award 受賞)
  • Takayuki Morioka, Ryuji Oshima, Ayami Takata, Yasushi Shoji, Tomoya Inoue, Takashi Kita, Yoshitaka Okada “Multi-staqcked InAs/GaNAs quantum dots with direct Si doping for use in intermediate-band solar cells” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010)
  • Shuhei Yagi, Yoshitaka Okada “Fabrication of resonant tunneling structures for selective energy contact of hot carrier solar cell based on III-V semiconductors” 35th IEEE Photovoltaic Specialists Conference, Hawaii (2010)
  • Shuhei Yagi, Ryuji Oshima, Yoshitaka Okada “Evaluation of selective energy contact for hot carrier solar cells based on III-V semiconductors” 34th IEEE Photovoltaic Specialists Conference, Philadelphia (2009)
  • Naoya Miyashita, Shuhei Ichikawa, and Yoshitaka Okada “Effect of Indium Composition on GaInNAsSb Solar Cells Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy” 34th IEEE Photovoltaic Specialists Conference, Philadelphia (2009)
  • Yasushi Shoji, Ryuji Oshima, Ayami Takatai, Akira Uedono, and Yoshitaka Okada “The effect of spacer layer thickness on vertical alignment of InGaAs/GaNAs quantum dots grown on GaAs(311)B substrate” The 14 th International Conference on Modulated Semiconductor Structures, Mo-mP41, Kobe (2009)
  • Ayami Takatai, Ryuji Oshima, Yasushi Shoji, and Yoshitaka Okada “Growth of multi-stacked InAs/GaNAs quantum dots grown with As2 source in atomic hydrogen-assisted molecular beam epitaxy” The 14 th International Conference on Modulated Semiconductor Structures, Mo-mP42, Kobe (2009)
  • Ryuji Oshima, Ayami Takatai, Yasushi Shoji, and Yoshitaka Okada “InAs/GaNAs strain-compensated quantum dots stacked over 50 layers for use in high-efficiency solar cell” The 14 th International Conference on Modulated Semiconductor Structures, Mo-mP50, Kobe (2009)
  • Ryuji Oshima, Ayami Takata, Yasushi Shoji, and Yoshitaka Okada “The effect of spacer layer thickness on the properties of quantum dot solar cells” 18th International Photovoltaic Science and Engineering Conference, Kolkata (2009) (Paper award 受賞)
  • Yasushi Shoji, Ryuji Oshima, Ayami Takatai, Akira Uedono, and Yoshitaka Okada “Fabrication of InGaAs/GaNAs strain-compensated quantum dot solar cell on GaAs (311)B substrate”　18th International Photovoltaic Science and Engineering Conference, 6-3p-023, Kolkata (2009)
  • Naoya Miyashita, Shuhei Ichikawa, and Yoshitaka Okada “Characteristics of GaInNAsSb Solar Cells Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy”, 2009 18th International Photovoltaic Science and Engineering Conference & Exhibition, 5-1o-014, Kolkata (2009)
  • Ryuji Oshima, Yasushi Shoji, Ayami Takata, and Yoshitaka Okada “Growth of InGaAs/GaNAs strain-compensated quantum dot superlattice on GaAs (311)B by molecular beam epitaxy” 15th International Conference on Molecular Beam Epitaxy, Vancouver, Canada (2008)
  • Ayami Takata, Ryuji Oshima, Yasushi Shoji and Yoshitaka Okada “Optical studies on InAs/InGaAs/GaNAs strain compensated quantum dots grown on GaAs(001) by molecular beam epitaxy” 15th International Conference on Molecular Beam Epitaxy, Vancouver, Canada (2008)
  • Ryuji Oshima, Ayami Takata, and Yoshitaka Okada “Increased photoabsorption in strain-compensated quantum dot solar cells” 17th International Photovoltaic Science and Engineering Conference, Fukuoka (2007)
  • Ayami Takata, Ryuji Oshima and Yoshitaka Okada “Growth of GaNAs films with As2 source in atomic hydrogen-assisted molecular beam epitaxy” International Conference on Solid State Devices and Materials, Tsukuba (2007)
  • Ryuji Oshima, Yuta Nakamura, Ayami Takata, and Yoshitaka Okada, “Multi-stacked InAs/GaNAs strain-compensated quantum dot solar cells” 22nd European Photovoltaic Solar Energy Conference and Exhibition, Milano (2007)
  • Naoya Miyashita, Yukiko Shimizu, and Yoshitaka Okada “Effect of increasing N composition on the performance of GaAs/GaInNAs heterojunction solar cells”, 2007 22nd European Photovoltaic Solar Energy Conference and Exhibition, 1CV.2.5, Milano, (2007)
  • Ryuji Oshima, Yuta Nakamura, Ayami Takata, and Yoshitaka Okada, “Optical properties of multi-stacked InAs/GaNAs strain-compensated quantum dots” 15th International Conference on Crystal Growth, Salt lake City (2007)

Books

Semiconductor Nanodevices, Edited by David A. Ritchie, Frontiers of Nanoscience Volume 20,
Yoshitaka Okada, Katsuhisa Yoshida, Yasushi Shoji, Ryo Tamaki (Role: Joint author, Chapter Ten – Semiconductor quantum dot solar cells)
ScienceDirect, Elsevier, Oct, 2021
  • 「量子ナノ構造太陽電池」岡田至崇、和田 隆博 監修｜「化合物薄膜太陽電池の最新技術 Ⅱ 第７章 超高効率太陽電池」pp．284-291, シーエムシー出版，2014)
  • “Intermediate Band Solar Cells” Yoshitaka Okada, Tomah Sogabe, and Yasushi Shoji, edited by A. J Nozik, G. Conibeer, and M. C. Beard | “Advanced Concepts in Photovoltaics”, pp.425-454，Royal Society of Chemistry, UK，2014
  • “Quantum Dot Solar Cells” Yoshitaka Okada, Katsuhisa Yoshida and Yasushi Shoji | edited by Laurentiu Fara and Masafumi Yamaguchi | “Advanced Solar Cell Materials, Technology, Modeling and Simulation”, pp.163-187，IGI Global, US，2013″
  • 「量子ドット型太陽電池開発の現状と課題」 岡田 至崇｜「高効率太陽電池　化合物・集光型・量子ドット型・Si・有機系・その他新素材」pp．167-176, エヌ・ティー・エス, 2012年
  • 「量子ドット太陽電池」 岡田 至崇 、桑野 幸徳、近藤 道雄 監修｜「図解　最新太陽光発電のすべて」pp．138-143, オーム社, 2011年
  • 「第3世代を目指す超高効率太陽電池」 岡田 至崇、小長井 誠，山口 真史，近藤 道雄 編著｜「太陽電池の基礎と応用」pp．220-226, 培風館, 2010年
  • 「量子ドット太陽電池　変換効率50％以上を目指す、革新的太陽電池技術」 岡田 至崇 ｜工業調査会, 2010年7月
  • 「解説：量子ドット超格子による高効率太陽電池の 開発」 岡田 至崇，八木 修平, 大島 隆治｜応用物理, 79, pp. 206-212 (2010)”
  • 「解説：量子ナノ構造を導入した次世代太陽電池」 岡田 至崇，大島 隆治 ｜応用物理, 76, pp. 50-53 (2007)”
  • 「解説：自己組織化量子ドット超格子と高効率太陽電池への応用」岡田 至崇｜日本結晶成長学会誌， 33, pp. 89-93 (2006)
  • 「解説：半導体量子ドットを用いた高効率太陽電池」 岡田 至崇｜電気学会誌，124, pp. 782-785 (2004)
  • 「光エレクトロニクス-展開編」 A. Yariv著，多田 邦雄，神谷 武志　監訳｜丸善，2000年11月
  • 「光エレクトロニクス-基礎編」 A. Yariv著，多田 邦雄，神谷 武志　監訳｜丸善，2000年3月
  • 「応用物理用語大事典」 応用物理学会編｜オーム社，1998年4月
  • 「オプトエレクトロニクス用語事典」 田中 俊一，末松 安晴，大越 孝敬　共編｜オーム社，1996年11月