Introduction to Solar Panel

How does a solar cell / semiconductor (SC) work?

Most solar cells are made of Silicon, which has four most outer electrons all involved in perfect covalent bonds. Hence a pure silicon crystal is an insulator. Si can be turned into SC by “doping”, which introduces small quantity of impurities to create free electrons or holes. N-type has free electrons, P-type has free holes.
At P/N junction, electrons and holes recombine and neutralize, leaving ionized “donors” and “acceptors”. This is the “depletion layer” where no mobile charge carriers are present.

When the sun shines…

Photon can knock an electron from its bond, creating an electron-hole pair. Electrons are holes are now free to move around inside crystal.
Because of the electric field at PN junction, electrons are drawn to the N-side, while the holes are drawn to the P-side. Electrons are collected by the thin metal fingers at the top of the cell and they flow through an external circuit, before returning through the back.

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What are Quantum Dots?

What are “Quantum dots”?

Quantum dots (QDs) are nanostructured semiconductors. QDs can be considered as an artificial atoms with electrons are “confined” inside
This can be done by encapsulating a material with smaller ECP (electrochemical potential), with a higher ECP material.
In this case, InAs for QDs and GaAs for substrate.

Energy potential in QD

Theoretically, “well” like energy potential confines electrons into nanometer space.Energy levels are quantized and electrons can only exist at certain energy levels. Energy level can be determined using Schrodinger’s equation.

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