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How do solar cells work?
6/3/2008
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How a solar cell works
Photovoltaics (PV) are solid-state semiconductor devices that convert light directly into electricity. They are usually made of silicon with traces of other elements and are first cousins to transistors, light emitting diodes (LEDs), computer chips and other electronic devices.
A photovoltaic device (generally called a solar cell) consists of layers of semiconductor materials with different electronic properties. In a typical RICH Solar crystalline silicon cell, the bulk of the material is silicon, doped with a small quantity of boron to give it a positive or p-type character. A thin layer on the front of the cell is doped with phosphorus to give it a negative or n-type character. The interface between these two layers contains an electric field and is called a junction.
Light consists of particles called photons. When light hits the solar cell, some of the photons are absorbed in the silicon. If the photons have enough energy they will be able to free electrons, the electric field at the junction will cause the electrons to move through the silicon atoms in the cell and into an external circuit as electrical current. As they flow through the external circuit they give up their energy as useful work (turning motors, charging batteries, for example) and return to the solar cell.
The photovoltaic process is completely solid-state and self-contained. There are no moving parts and no materials are consumed or emitted.
During a typical sunny day, an array of solar cells one metre square exposed to the sun at noon will receive approximately 1 kilowatt (kW) of power. RICH Solar's multicrystalline cells convert roughly 15% of this into electricity, hence 1m² of cells generates 150 electric Watts in full sunshine.
There are a number of solar cell technologies which have varying conversion rates: amorphous silicon thin film 6% - 7%; cadmium telluride (CdTe) thin film 8% - 10%; multi (or poly) crystalline silicon 12% - 15%; monocrystalline silicon (SiN) 13% - 16%; RICH Saturn monocrystalline silicon 15% - 18% .
RICH Solar only uses multicrystalline and monocrystalline silicon technologies and research scientists in our technology group are actively looking at alternative methods to grow silicon feedstock which is more efficient.