Dual-Path Optimization Strategy for High-Efficiency Chalcogenide Perovskite Solar Cells: Bulk Bandgap Engineering and Advanced Interfacial Design

Chalcogenide perovskites offer a stable, high-performance alternative to hybrid perovskites. However, the full optoelectronic potential associated with their tunable bandgap remains underutilized. This study introduces a dual-path optimization strategy in lead-free BaZr1-xTixS3 chalcogenide perovskite that synergistically combines the implementation of a compositionally graded bandgap in BaZr1-xTixS3 using a β-function profile with advanced interfacial design and the insertion of WS2 electron transport layer (ETL). Precise control of the Zr/Ti compositional gradient within the absorber, governed by a β-function profile (x: 0–0.6), establishes a continuous internal energy field that enhances broadband photon harvesting and promotes efficient charge separation. Concurrently, the integration of WS2 in FTO/WS2/BaZr1-xTixS3/Cu2O/Au suppresses interfacial recombination and facilitates efficient charge extraction, thereby reducing charge loss. Solar Cell Capacitance Simulator – One Dimension (SCAPS-1D) simulations under AM1.5G illumination indicate that this co-optimized architecture can achieve a power conversion efficiency (PCE) of 24.22%. These results demonstrate that coordinated optimization of the absorber’s electronic landscape and the charge-selective contact is critical for unlocking the high-efficiency potential of emerging perovskite-inspired materials, providing a holistic design framework for next-generation photovoltaics.