Numerical Investigation of Interface Passivation Strategies for Sb2Se3/CdS Solar Cells

Sb2Se3 is an emerging earth-abundant material praised for its promising optoelectronic properties, although the presence of interfacial defects at the vicinity of the p-n junction limit its performance as photovoltaic absorber. Using a device modeling approach and a realistic set of material parameters, it unravels pathways mitigating the impact of interfacial defects with a baseline Sb2Se3/CdS. Two straightforward strategies are devised and tested against the baseline. First, a thin front surface sulfurization of the Sb2Se3 absorber allowing a local lowering of the valence band and creating a "front surface field," resulting in an increased carrier selectivity and limiting the density of holes available for interface recombination, leading to a significant efficiency improvement for optimized conditions. Second, the use of an ultrathin insulating Al2O3 layer between the absorber and the buffer layer is considered, helping in preventing detrimental chemical interdiffusion at the junction. This strategy provides a direct interface passivation, though the interlayer thickness needs a fine tuning to balance the benefits of reduced interface recombination and a detrimental Al2O3 low-conductivity layer. In each case, an analysis covering a broad range of parameters is presented, and conclusions are made in the frame of past numerical and experimental results.