Solar-energy Conversion by Photovoltaic Cells

In doped silicon (an extrinsic semiconductor) the doping element has either three or five valence electrons (one electron less or one electron more than the four valence electrons of silicon). Substituting an arsenic or phosphorus atom (five valence electrons) for a silicon atom in a silicon crystal provides an extra loosely-bound electron that is more easily excited into the CB than in the case of the pure silicon. In such an n-type semiconductor, most of the electrical conductivity is attributed 

When photons are absorbed by the p-n junction, it acts as a photovoltaic cell at which electrons are promoted from the VB to the CB, forming an electron-hole pair. Connecting the p- and n-type silicon via 

While the application of photovoltaic cells has been dominated by solid-state junction devices principally made from silicon, recent work in this field offers the prospect of efficient solar-energy conversion by novel methods. 

---