Interface engineering of halide perovskite-based solar cells

Abstract

Perovskite solar cells (PSCs) have attracted widespread attention as next-generation photovoltaic technologies due to their high power conversion efficiencies, low-cost fabrication, and solution-processable nature. However, challenges such as phase instability and defect-induced recombination continue to limit their commercial viability. In this work, the primary goal was to stabilize the photoactive α-phase of formamidinium lead iodide (FAPbI3), which is essential for achieving efficient and stable PSCs. To accomplish this, compositional engineering was employed—first through partial substitution with methylammonium (MA+), followed by the development of a triple-cation perovskite incorporating cesium (Cs+), resulting in the composition-Cs0.05FA0.81MA0.14PbI2.55Br0.45. All devices were fabricated via a solution based method inside a nitrogen-filled glovebox to preserve film quality. Devices based on FA/MA compositions achieved a power conversion efficiency (PCE) of 13.33%, while triple-cation devices showed significantly improved performance, reaching a PCE of 17.46%, with enhanced Jsc, Voc, and fill factor. To further reduce non-radiative losses and passivate interfacial defects, formamidinium acetate (FAAc), an ionic liquid, was introduced as an interface modifier. FAAc-treated devices exhibited improved Voc and film uniformity, with a champion PCE of 11.15%. This study demonstrates the effectiveness of combining compositional tuning and interfacial engineering to enhance both efficiency and stability in PSCs. The findings provide valuable insights into phase stabilization, defect passivation, and interface optimization strategies for high-performance perovskite photovoltaics.