Synergetic interfacial passivation, band alignment, and long-term stability with halide-optimized CsPbBrxI3−x nanocrystals for high-efficiency MAPbI3 solar cells

Abstract

Interfacial engineering has been proved as an effective strategy to passivate grain boundaries and surface defects for high performance solar cells. Herein, we report a nanocrystal interfacial engineering strategy using CsPbBr_xI_3−x as an interface modifier to increase the efficiency of MAPbI₃-based solar cells. The CsPbBr_xI_3−x modification layer decreased the trap states, improved the energy alignment of the device, and enhanced the interfacial charge transfer and carrier extraction. Morphology and stability assessment demonstrated that the CsPbBr_xI_3−x modification reduces the surface roughness and enhances the environmental stability of photoactive MAPbI₃ layers. The Br/I ratio was optimized to facilitate the energy-level matching with absorbers and hole transporting layers, which demonstrated the effectiveness of the trap state suppression and non-radiative recombination reduction. These merits facilitated the hole extraction rate so that the champion device achieved a power conversion efficiency of 19.16% with reduced hysteresis and long-term stability 16.06% greater than that of the unmodified device. Our work provides an effective and versatile perovskite nanocrystal interfacial engineering strategy that is important for the design of high-performance and long-lasting perovskite optoelectronic devices.