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The solar radiation spectrum shows that maximum solar intensity is near to energy hv = 1.5 eV. Answer the following: (i) Why are SI and GaAs are preferred materials for solar cells. (ii) Why CdS or CdSe are preferred materials for solar cells. (iii) Why we do not use materials like PbS (Eg ~ 0.4 eV). |
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Answer» Solution :(i) For photo-excitation, hv `gt` Eg. SI has Eg. ~ 1.1 EV and for GAAS, Eg. ~ 1.53 eV. GaAs is better than Si because of its relatively higher absorption coefficient. (ii) If we choose CdS or CdSe, we can use only the high energy component of the solar energy for photo-conversion and a significant part of energy will be of no use. (iii) The CONDITION `hv gt Eg`. is satisfied, but if we use Pbs, most of solar radiation will be absorbed on the top-layer of solar cell and will not reach in or near depletion region. |
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