The injected dark current of a p+n and a p+n n+ silicon solar cell taking into account the narrowing of band gap due to heavy doping

Abstract

In addition to the photocurrent, the dark current of solar cell plays a vital role in determining the overall efficiency of a solar cell. In this paper, the injected dark current of a p⁺ n junction solar cell and that of a p⁺ n n⁺ back-surface-field cell have been studied analytically, taking into account the band gap narrowing effect that exists at high doping concentrations. It is observed that there is a significant difference in the magnitude of the injected dark current obtained when the band gap narrowing effect is taken into consideration as compared to the case when it is not considered. Also, it is observed that the magnitude of the injected dark current decreases for smaller values of back surface recombination velocity, which corresponds to BSF structure. This is one of the reasons why the p⁺ n n⁺ BSF solar cell has better output than the conventional p⁺ n cell. The results obtained here are similar to the case of an n⁺ p p⁺ solar cell reported earlier by researchers.