Simulation‐Driven Bandgap Optimization of Absorber Layer Cs _<i>x</i> (FA _0.88 MA _0.12 ) _{1− <i>x</i>} Pb(I ₁₋ _<i>y</i> Br _<i>y</i> ) ₃ for 25.8% Efficient n

This study explores the optimization of triple cation (CsFAMA) mixed halide (I, Br) perovskite solar cells through cation engineering and halide tuning via comprehensive simulations. Cs x (FA 0.88 MA 0.12 ) 1 −x Pb(I 1 −y Br y ) 3 is modeled as the absorber layer, achieving a tunable bandgap range of 1.58–1.74 eV. Considering the exceptional stability of triple‐cation perovskites, the objective is to determine the optimal bandgap and the material properties for single‐junction solar cell applications, ensuring their suitability for real‐world industrial deployment in thin‐film n‐i‐p solar cells. A thorough evaluation of various hole transport/selective layers (HTLs), including Spiro‐OMeTAD, CuSCN, Cu 2 O, and NiO x , alongside electron transport/selective layers (ETLs), such as SnO 2 and TiO 2 , is conducted. The exhaustive analysis transcended standard J – V characterization, incorporating C–V and I–S measurements to unravel the intricate device physics—a dimension often over looked in current research. The stand out device, utilizing TiO 2 as the ETL and NiO x as the HTL, showcased an extraordinary power conversion efficiency (PCE) greater than 27% (under ideal operating conditions) and a PCE of more than 25% (under simulated outdoor condition) with a bandgap of 1.58 eV. These compelling findings highlight the tremendous potential of the meticulously optimized perovskite composition, pointing toward an era of high‐efficiency, commercially viable solar cell technology.