Maximum efficiency of a Silicon photovoltaic cell. The energy gap of Silicon is
ID: 2082550 • Letter: M
Question
Maximum efficiency of a Silicon photovoltaic cell.
The energy gap of Silicon is 1.1 eV. This implies that not all photons emitted by the Sun can be
absorbed.
a. Estimate the fraction of the solar spectrum that can actually excite electrons from the valence
band to the conduction band in Silicon. For this you need to approximate the solar
spectrum with that of a black body.
b. The efficiency of standard Silicon solar cells is 15%. How does this value compare with the
value you have calculated in a) ? Calculate what you would really expect in this case.
c. The solar spectrum measured at the Earth surface is different from that of an ideal black
body due to absorption by specific molecules in the atmosphere. Does this change your
conclusions in b) ?
Explanation / Answer
Solar energy is same like carbon based fuel sources.Most of the humanbeings consumes enenrgy which is available in the form of fossil fuels.They are mostly converted into CO2 and causes maximum of climatic changes.Mostly the sun delivers high amount of energy on to the eaarth so that this energy can be converted into different forms of electrical and chemical energies.
a)The fraction of solar spectrumm cannot be estimated exactly which actually excite electrons from a valency band to conduction band.In some cases the fraction of solar spectrum can be estimated which is mainly available in the band of silicon. The black body is highly frictionate to the solar spectrum and through this we can estimate the band fraction of solar and maintain the valency of the band.
b)The comparision of standard silicon and solar spectrum is quite difficult but by maintaining the valencies of both the standard silicon solar cells and the solar spectrum can be evaluated.In this case we mostly expect the electrons which have been ready to excite the valency of solar spectrum and maintain their band width.
c)As i mentioned in the above two sub parts the valencies and the band width can be maintained i the spectrum so that the specific molecules which have been absorbed whn the earth surface is measured but if the black body valency and the solar spectrum is actually maintain their electrons then there wil ne no change in the specific molecules of the black body and the solar spectrum measured at the earth surface.