A Sustainable Double‐Absorber Perovskite Solar Cell Based on Ca ₃ NBr ₃ and Ca ₃ NCl ₃ Achieving 35.76% Efficiency

This research focuses on improving solar cell efficiency and environmental sustainability by introducing a new type of tandem perovskite solar cell (PSC) that uses Ca 3 NBr 3 and Ca 3 NCl 3 as two active absorbing layers. The design was simulated using SCAPS‐1D software and includes an fluorine‐doped tin oxide (FTO) base layer, CdS as the electron transport layer (ETL), V 2 O 5 as the hole transport layer (HTL), and carefully selected absorber materials. The study closely examines how factors like absorber thickness, defect levels, and doping concentrations affect the device’s overall performance. The best‐performing model, with 500 nm thick absorbers and low interface defects, reached an impressive efficiency of 35.76%, a current density of 35.06 mA/cm 2 , a voltage of 1.23 V, and a fill factor (FF) of 83.18%. The impact of temperature and electrical resistance was also analyzed, showing that low series resistance and stable temperature conditions are essential for high performance. These results highlight the strong potential of Ca 3 NBr 3 /Ca 3 NCl 3 based tandem solar cells as a promising and lead‐free solution for the next generation of high‐efficiency photovoltaic (PV) devices.