Simulation Study of a Gradient‐Engineered 2D DJ–3D Hybrid Perovskite Solar Cell Architecture

This study presents a high‐efficiency perovskite solar cell design that combines a lead‐free chalcogenide absorber with a lead‐based 2D perovskite secondary absorber to achieve enhanced performance and stability. The proposed device employs Ba(Zr, Ti)S 3 as the primary 3D absorber and a graded PeDA‐based Dion–Jacobson (DJ) 2D perovskite as the secondary absorber layer. The 3D chalcogenide provides excellent optical absorption and efficient charge transport, while the 2D DJ layer contributes strong light‐harvesting ability, environmental stability, and effective carrier confinement. Bandgap grading is used within the 2D layer for creating a gradual energy transition across the absorber layer that leads to improvement in carrier extraction and minimizes recombination losses at the interface. Two grading profiles were considered: linear and parabolic for numerical simulations of the device. The influence on recombination‐generation behavior, transport characteristics, and photovoltaic parameters was analyzed. The linear graded configuration achieved the highest performance, with PCE = 26.48%, V OC = 1.11 V, J SC = 26.96 mA/cm 2 , and FF = 88.6%. In contrast, the parabolic graded structure yielded PCE = 25.96%, V OC = 1.11, J SC = 26.5 mA/cm 2 and FF = 88.4%. The findings demonstrate that smooth bandgap grading in the 2D DJ absorber facilitates balanced carrier flow and reduces interfacial recombination, providing an effective route toward high‐performance and eco‐friendly hybrid perovskite solar cells.