A Comparative Study of High-Efficiency Lead-Free Cs3Bi2X9 (X = Cl, Br, I)-Based Solar Cells

Lead halide-based perovskite solar cells have gained significant attention from academia and the photovoltaic industry due to their exceptional optical and electrical characteristics. The primary problem with Pb-based perovskite pertains to its toxicity and solubility in water within the external environment. These concerns regarding hazards to the environment are constraining the application of lead-based perovskite in both consumer and industrial contexts. To offer a viable alternative to lead-based hazardous perovskite solar cells, we examined an inverted (p-i-n) perovskite structure with three distinct absorber layers based on cesium bismuth halides (Cs3Bi2I9, Cs3Bi2Cl9, Cs3Bi2Br9) and conducted a comparative analysis utilizing SCAPS-1D software (version 3.3.08). The comparison analysis of our design against starting parameters indicated that the optimal power conversion efficiency (PCE) of 10.01% was recorded for Cs3Bi2I9, 7.56% for Cs3Bi2Br9, and 4.34% for Cs3Bi2Cl9. Following careful optimization of the thickness of charge-transport layers (CTLs), doping concentrations of CTLs, and all three absorber layers, the overall efficiencies of the three inverted structures were enhanced from 10.01% to 14.08% for Cs3Bi2I9, from 4.34% to 5.28% for Cs3Bi2Cl9, and from 7.56% to 11.05% for Cs3Bi2Br9, respectively. The other performance enhancement, open-circuit voltage, increased from 1.08 V to 1.37 V for Cs3Bi2I9, from 1.26 V to 1.47 V for Cs3Bi2Cl9, and from 1.20 V to 1.47 V for Cs3Bi2Br9. This comparative analysis of proposed perovskite devices demonstrates that Cs3Bi2X-based perovskite devices possess significant potential to replace conventional hazardous solar cells in the renewable and clean energy sectors.