On the possibility of improving silicon solar cell efficiency through impurity photovoltaic effect and compensation

The possibility of improving silicon (Si) solar cell efficiency through combined impact of impurity photovoltaic effect (IPV) and compensation is investigated. In the mechanism presented here, the IPV effect is produced by a deep level impurity, while the compensation is achieved through some other shallow level impurity. It has been pointed out that compared to the primary dopant, the deep level impurity concentration must be kept moderate, such that it is presence does not deteriorate the carrier lifetime. In presence of moderate concentration of deep impurity, shallow level impurities can be effectively deployed to improve the carrier lifetime through compensation and this can lead to overall enhancement of solar cell efficiency. Results have been presented to validate the concept with a cell having a compensated boron (B) doped base, which also contains moderate concentration of chromium (Cr) that absorbs sub-bandgap photons.