Design and performance optimization of a novel tri-layer unleaded all inorganic lead-free mixed halide CsSnI3-x Brx heterojunction solar cell

Perovskite solar cells (PSCs) have demonstrated commendable efficiency, yet grapple with challenges pertaining to stability and toxicity, largely attributed to the prevalent use of hybrid organic-inorganic and lead-based materials. This study strategically shifts the focus from methylammonium-lead-based (MA-Pb) PSCs to their cesium-lead- (Cs-Pb) free counterparts, aiming to address these persistent issues. In the pursuit of a balanced interplay between efficiency and stability, the study employs CsSnBr3, CsSnIBr2, and CsSnI2Br as perovskite absorber layers. CsSnBr3 enhances stability, CsSnIBr2 improves both efficiency and stability, while CsSnI2Br predominantly enhances efficiency, collectively providing a favorable equilibrium. To optimize PSC efficiency, the research explores multi-layer configurations to enhance solar-spectrum absorption, with the goal of maximizing spectrum utilization and improving the overall efficiency of PSCs. The study systematically assesses single, bilayer, and tri-layer PSCs. Initial simulations rigorously evaluate the performance of single layer PSC based on CsSnBr3, CsSnIBr2, and CsSnI2Br. Subsequently, a bilayer PSC is simulated, incorporating CsSnBr3 and CsSnIBr2 as absorber layers, with meticulous optimization of its performance. The research concludes by simulating a tri-layer PSC, utilizing CsSnBr3, CsSnIBr2, and CsSnI2Br as absorber layers, with optimization across various variables, including absorber layer thickness, bulk defect density, interface defect density, and doping concentration for both bilayer and triple-layer PSCs. The study reveals remarkable efficiencies of 9.12 %, 22.81 %, and 32.82 % for single layer PSC, bilayer PSC and the tri-layer PSC respectively. These findings underscore the transformative potential of strategically aligned multiple absorber layers in PSCs, providing a promising pathway for the development of highly efficient and stable solar cells in the future.