Effect of MoS₂ Interfacial Engineering across MAPbI₃, FAPbI₃, and CsPbI₃ Perovskite Solar Cells

Perovskite solar cells have achieved rapid efficiency gains; however, interfacial recombination and energy-level mismatch remain major factors limiting performance consistency and stability. This work presents a systematic numerical investigation of interface engineering in perovskite solar cells using SCAPS-1D simulations. Three absorber materials of methylammonium lead iodide (MAPbI₃), formamidinium lead iodide (FAPbI₃), and cesium lead iodide (CsPbI₃) are examined within an identical device configuration employing TiO₂ as the electron transport layer and spiro-OMeTAD as the hole transport layer. A thin molybdenum disulfide (MoS₂) layer is introduced between the absorber and the hole transport layer to evaluate its influence on the band alignment, electric potential distribution, and photovoltaic performance. The results show that MoS₂ modifies the valence band alignment at the back interface, increasing the local electric potential and supporting an improved charge separation. Devices incorporating MoS₂ exhibit enhanced short-circuit current density, fill factor, and power conversion efficiency across all absorber compositions. Efficiency improvements from 19.28% to 21.54% for MAPbI₃, from 20.10% to 22.25% for FAPbI₃, and from 15.32% to 18.25% for CsPbI₃ were observed. Parametric analyses further indicate an improved tolerance to variations in absorber thickness, doping concentration, temperature, and bulk defect density in MoS₂-integrated structures. These findings demonstrate that MoS₂-based interface modification offers a consistent pathway to reduce interfacial losses and improve the photovoltaic performance across hybrid and all-inorganic perovskite solar cells.