Electronic loss mechanisms in chalcopyrite based heterojunction solar cells

This article discusses the fundamental limitations imposed on Cu(In,Ga)Se2 based heterostructure solar cells by recombination in the bulk of the absorber and at the interface between the absorber and the CdS buffer layer. Bulk recombination to a certain extent can be minimized by increasing the doping density up to a limit where tunneling currents significantly enhance recombination. We propose simple schemes for the analysis of experimentally gained data. By comparison of theoretical models with experimental data we show that tunneling plays a role for polycrystalline Cu(In,Ga)Se2 in some cases and for CuGaSe2 in general.