Solar Cell Working Principles
A semiconductor solar cell is essentially a large p-n junction, operating according to the same principles regardless of its material type through three steps:
Charge carrier generation: Incident sunlight is absorbed by the semiconductor, exciting electrons from the valence band to the conduction band and creating electron-hole pairs.
Charge carrier separation: The built-in electric field at the p-n junction drives the separation of electrons and holes: holes are pushed toward the p-type, and the electrons are pushed toward the n-type. The separation minimizes recombination of the charge carriers, allowing their movement.
Transport and collection of charge carriers: The separated electrons flow through the external circuit toward the p-type side, delivering usable electrical energy, while holes move internally toward the p-type contact. At the p-type contact, electrons recombine with holes, completing the circuit.
The figure below illustrates the cycle of generation and separation of electron-hole pairs in a PN junction under illumination.
