Alexandre Edmond Becquerel, a French physicist, discovered photovoltaic effect in 1839 and thus unraveling the key principle to today's solar energy cells. In this, the supply of light and/or heat releases positive and negative charge carriers (photovoltaic effect), generating electricity which can directly charge batteries and power motors. This direct conversion of sunlight into electricity ( Photovoltaics ) has continually been developing in recent decades. The advantage of photovoltaics is generating clean, environmentally-friendly electricity independent of the utility grid.Today's solar cells are made almost entirely from semiconductor silicon. This atom exists in the form of silicon dioxide (quartz, sand) as unprocessed raw material in the earth's crust. It is the second most common element after oxygen. Silicon dioxide can be processed into monocrystalline, polycrystalline, or amorphous silicon. The differences lie in the respective energy conversion efficiency, which is crucial for the performance of a solar cell. Solar cells made of amorphous silicon have the lowest energy conversion efficiency and solar cells made of monocrystalline silicon have the highest energy conversion efficiency.