Phase-Pure 2D Interfacial Perovskite Passivation for Stable and Efficient Photovoltaics

Abstract

Phase-pure two-dimensional (2D) interfacial passivation has emerged as an effective strategy for addressing the intrinsic instability and interfacial defects of three-dimensional (3D) perovskite absorbers. However, conventionally formed 2D layers often suffer from mixed-n phases, heterogeneous quantum-well distributions, and disordered orientation, which impede charge transport, distort energy-level alignment, and accelerate structural degradation. In this review, we elucidate the thermodynamic and kinetic origins of mixed-phase formation and discuss how dimensional heterogeneity adversely impacts carrier dynamics and device stability. We then summarize recent advances in achieving phase-pure 2D perovskite interlayers that enable precise n-value control, favorable crystal orientation, and optimized interfacial energetics. These strategies yield highly ordered 2D/3D heterostructures that effectively suppress ion migration, mitigate non-radiative recombination, and significantly enhance long-term operational stability. Finally, we outline the remaining challenges and emerging opportunities for scalable, phase-pure engineering toward high-efficiency and stable perovskite photovoltaic technologies. Overall, this review provides a unified framework linking phase purity, interfacial ordering, and device stability, offering guidance for the development of next-generation robust perovskite photovoltaics.