Unlocking High Efficiency in Sb2S3 Solar Cells by Decoding the CdS/Sb2S3 Interface Dynamics

Abstract Antimony sulfide (Sb2S3) is a promising candidate for sustainable photovoltaics due to its earth abundance, low toxicity, and unique quasi-one-dimensional crystal structures. However, the conversion efficiency of CdS/Sb2S3 devices is severely bottlenecked by a severe open-circuit voltage deficit, arising from the intricate multivariable coupling between conduction band offset, buffer thickness, and doping, which governs the competitive balance between interfacial recombination activation energy and field-driven carrier separation kinetics. Here, we employ SCAPS-1D simulation to systematically decode these synergistic dynamics and establish a doping-dependent design paradigm for interface engineering. Our results reveal that for lightly doped CdS, a thicker buffer (∼60 nm) with a “spike” configuration is essential to boost the built-in field (Vbi) and suppress recombination. Conversely, for heavily doped CdS, an ultrathin buffer (∼20 nm) with a weak “cliff” structure achieves optimal performance by minimizing parasitic absorption and transport resistance. These insights unravel the physical origins of performance limits and provide precise, quantitative design guidelines for rational interface engineering, paving a robust pathway toward high-efficiency Sb2S3 solar cells.