Exploring Multi-Level ETL and HTL Configurations for High-Efficiency Lead-Free Cs2AgBiBr6 Double Perovskite Solar Cells: A Design and Simulation Study

Cs₂AgBiBr₆ is a promising lead-free double perovskite solar cells (PSCs) material. Its full potential has yet to be realized due to issues with its large band gap and the optimization of the alignment of the electron transport layer (ETL) and hole transport layer (HTL). The photovoltaic performance of Cs₂AgBiBr₆-based devices has been optimized using ZnO, IGZO, TiO₂, WS₂, PCBM, and C₆₀ ETLs and Cu₂O, CuScN, CuSbS₂, NiO, P3HT, PEDOT: PSS, Spiro MeOTAD, CuI, CuO, V₂O₅, CBTS, and CFTS HTLs. It has been observed by simulation study that Cs₂AgBiBr₆-based devices exhibit remarkably high photoconversion efficiency when combined with certain ETLs. To better understand the performance, we examine how the best device structures are affected by the absorber and ETL thickness, ETL carrier density, series and shunt resistance, generation, and recombination rate. The findings suggest that TiO₂ and ZnO ETLs, in conjunction with CBTS HTL, exhibit good potential for producing high-efficiency (η > 13%) Cs₂AgBiBr₆-based heterojunction solar cells with an ITO/ETL/Cs₂AgBiBr₆/CBTS/Au device structure. Optimization of the valence band offset (VBO) at the CBTS/Cs₂AgBiBr₆ interface reveals that reduced VBO value has a beneficial impact on the performance of the solar cell. This modeling work gives a prospective route for manufacturing lead-free Cs₂AgBiBr₆ PSCs.