Space charge region recombination, non-radiative exciton recombination and the band-narrowing effect in high-efficiency silicon solar cells

Abstract

An expression for finding the dependence of narrowing the bands in silicon ΔEg on the level of illumination from the intrinsic absorption band (or short-circuit current) has been proposed. This expression is used to find experimental values of ΔEg in high-efficient silicon solar cells. The dependence ΔEg (J) or dependence ΔEg (JI), where JI is the short-circuit current density, has been rebuilt into the ΔEg (ΔnOC) dependence, where ΔnOC is the excitation level in open-circuit conditions. With this aim, the generation-recombination balance equation was solved taking into account six recombination mechanisms in silicon, including Shockley–Reed–Hall recombination, radiative recombination, interband Auger recombination, surface recombination, non-radiative exciton recombination, and recombination in the space charge region. The latter two recombination terms are not taken into account in studies of the key parameters of silicon solar cells and in programs for simulating the characteristics of these solar cells. Therefore, in this work their correct definition was performed, their contribution was compared with the contribution of other recombination mechanisms, and it has been shown that the description of the characteristics and key parameters of silicon SC without taking them into account is insufficiently correct. The experimental dependences ΔEg (ΔnOC) obtained in the work were compared with Schenk’s theory. It has been shown that there is a good agreement between them.