5.11. Electron reflector
The record efficiency of CdTe solar cell is 16.5% while theoretical efficiency is 29% and this is recorded at open circuit voltage of 0.845 V, which gives efficiency lower than the expected at band gap of 1.5 eV. Most of incident solar light is absorbed at ~600 nm and has large optical absorption [92]. To increase the open circuit voltage and conversion efficiency one has to increase charge carrier density and lifetime and electron reflector is used at the back contact of cell in order to accomplish this [93]. The electron reflector method is more practical and less costly. Under forward biased condition electron reflector will reflect minority carrier electrons and thus reduce the back surface recombination. Electron reflector can be formed by adding a layer of p-type material with large band gap at back surface of CdTe absorber. Mostly CdZnTe and CdMgTe are used as ER [94].