The photovolataic effect is the means by which the photovoltaic cells ( the first generation of solar cell ) are able to transform sunlight into electricity.
A photovoltaic cell is made from a thin slice of semiconductor, usually silicon or galium-arsenide. Two special types of impurities called dopants are added to the semiconductor. The upper and lower part of the slice become respectively a p-type and n-type semiconductor. The n-type has a surplus of electrons while the p-type has a lack of electorns – also called “holes”. This electron imbalance forms an electric field in the semiconductor slice.
When an electron is hit by a photon it becomes free of the p-n structure leaving a “hole” or positive charge behind. Being in an electric field he negative electron and the positive “hole” begin to move in oposite directions creating an electric current. If we connect wires to the semiconductor we can run this current through a load ( light bulb, battery charger, etc ).
Of course not all the photons hit the electrons in the solar cell. Some light bounces right off the cell and some misses the electrons and passes right through. Also the semiconductors used today are able to absorb just about half the spectrum of sunlight, further limiting the efficiency of cells.
The efficiency of photovoltaic cells can be raised using different combinations of semiconductors to try to absorb the whole length of the sun’s specturm and also use thicker slices with more p-n junctions to catch the photons that pass thorough the first junction.
