A co-design strategy for chalcogenide perovskite solar cells: Synergistic bandgap grading and interface optimization

This study provides a comprehensive device-level optimization blueprint for the emerging chalcogenide perovskite solar cells. While bandgap grading and contact engineering are established concepts, their synergistic application and quantitative optimization in this specific material system remain unexplored. We demonstrate that spatially grading the S/Se composition using power-law and beta-function profiles fundamentally reshapes the absorber's electronic landscape, enhancing carrier collection and boosting efficiency from 8.91% (uniform) to 26.16%. Concurrently, we establish optimal interface design rules, showing how hole transport layer bandgap, doping, and back contact work function collectively minimize interfacial losses. Our work transcends a simple parameter scan; it delivers a co-optimized, high-efficiency device architecture (26.16% PCE ) that serves as a tangible target and a practical fabrication guide for experimentalists pursuing stable, high-performance chalcogenide perovskite photovoltaics.