Quantitative determination of optical and recombination losses in thin-film photovoltaic devices based on external quantum efficiency analysis

摘要

In developing photovoltaic devices with high efficiencies, quantitativedetermination of the carrier loss is crucial. In conventional solar-cellcharacterization techniques, however, photocurrent reduction originating fromparasitic light absorption and carrier recombination within the light absorbercannot be assessed easily. Here, we develop a general analysis scheme in whichthe optical and recombination losses in submicron-textured solar cells areevaluated systematically from external quantum efficiency (EQE) spectra. Inthis method, the optical absorption in solar cells is first deduced by imposingthe anti-reflection condition in the calculation of the absorptance spectrum,and the carrier extraction from the light absorber layer is then modeled byconsidering a carrier collection length from the absorber interface. Ouranalysis method is appropriate for a wide variety of photovoltaic devices,including kesterite solar cells [Cu2ZnSnSe4, Cu2ZnSnS4, and Cu2ZnSn(S,Se)4],zincblende CdTe solar cells, and hybrid perovskite (CH3NH3PbI3) solar cells,and provides excellent fitting to numerous EQE spectra reported earlier. Basedon the results obtained from our EQE analyses, we discuss the effects ofparasitic absorption and carrier recombination in different types of solarcells.