Efficiency enhancement via novel lead-free inorganic CsSnBr3/Cs3Bi2I9 heterojunction absorber layer in perovskite solar cell

Abstract

In this work, we introduce a novel simulation approach that leverages the potential of a lead-free CsSnBr₃/Cs₃Bi₂I₉ perovskite heterojunction as the absorber layer, integrated into a high-performance all-inorganic device architecture consisting of FTO/TiO₂/Absorber/CuSCN/Au. This approach aims to extend the absorption range of the solar spectrum. It allows for comparing single-junction devices with Cs₃Bi₂I₉ as the absorber layer, helping to assess improvements in photovoltaic parameters. When the device utilizing Cs₃Bi₂I₉ as the absorber layer was simulated under constant parameters, it demonstrated impressive performance metrics, achieving an open-circuit voltage of 1.33 V, a short-circuit current density of 11.56 mA/cm², a fill factor of 61.12 %, and a power conversion efficiency of 9.42 %. In contrast, when the heterojunction CsSnBr₃/Cs₃Bi₂I₉ absorber layer was used, a notable improvement in photovoltaic parameters was observed, with a V_OC of 1.32 V, J_SC of 19.76 mA/cm², and FF of 68.2 %, resulting in a PCE of 17.81 %. This indicates a significant enhancement in the performance of solar cell devices. We also investigated the combined effects of the thickness of the bi-absorber layer and defect density using contour plots. The defects at the CsSnBr₃/Cs₃Bi₂I₉ interface, series and shunt resistance, capacitance and Mott-Schottky behaviour, charge generation and recombination, and temperature were studied to understand the impact of these parameters on perovskite solar cells device performance. Overall, this work explores the advantages of the CsSnBr₃/Cs₃Bi₂I₉ heterojunction absorber layer approach, which opens new pathways for researchers to improve the performance of inorganic PSCs.