Layer Distortion Engineering for Spontaneous Charge Separation in Two-Dimensional Perovskites

Abstract

Charge separation in highly confined type-I two-dimensional (2D) perovskites with a single inorganic layer (n = 1) remains challenging due to their excessive exciton binding energy. Herein, we engineer the layer distortion within Ruddlesden–Popper (RP) type perovskites (n = 1) by tailoring the sizes of the cycloalkylamine ligands. The perovskite layers are more distorted and corrugated to accommodate the highly compact yet rigid cyclopropylammonium and cyclobutylammonium, facilitating the formation of Pb–Pb and I–I ionic dimers as self-localizing sites for charge carriers. Consequently, spontaneous electron–hole separation as well as a long-lived (>1 μs) intrinsic quantum confined Stark effect (QCSE) is achieved using the thresholdless optical pump and without applying any external electric field, yielding an unprecedent amount of the photoinduced bandgap energy lowering. This work opens up new possibilities of efficient charge separation in type-I 2D quantum wells for the photovoltaic and nonlinear optical modulation applications.