Theoretical and experimental investigation of air-processed Cs₂AgBiBr_5.5I_0.5 lead-free double perovskite for photovoltaic applications

Lead-free inorganic perovskite material, such as Cs₂AgBiBr₆, must be developed to address the toxicity and stability issues associated with conventional lead halide perovskite solar cells (PSCs). Nevertheless, the Cs₂AgBiBr₆ film’s broad bandgap diminishes its capacity to absorb light, leading to generally lower power conversion efficiency (PCE) than its competitors. Anionic alloying (halide mixture) can effectively modify the optoelectronic properties of lead-free halide double perovskites (DPs), including the band gap. The potential of lead-free DPs that have been air-processed, specifically Cs₂AgBiBr_5.5I_0.5, has been examined in this study using both theoretical and experimental methodologies. The material was facile to fabricate in an ambient environment and exhibited exceptional thermal stability. In both theoretical and experimental investigations, the Cs₂AgBiBr_5.5I_0.5 perovskites have been demonstrated to possess a reduced bandgap and an increased light-absorbing capacity. The performance of Cs₂AgBiBr_5.5I_0.5 PSCs was substantially influenced by the metal work function, defect density, acceptor density, and temperature of the charge transporting layers (CTLs) as demonstrated by the SCAPS-1D simulations. The optimized device, which utilized an absorber layer of Cs₂AgBiBr_5.5I_0.5 perovskite, exhibited an exceptional PCE of 16.9%. Our research suggests that the halide alloying procedure may be a viable method for enhancing the stability and performance of lead-free DPs.