Nucleation‐Controlled Crystallization of Chiral 2D Perovskite Single Crystal Thin Films for High‐Sensitivity Circularly Polarized Light Detection

Abstract 2D Dion−Jacobson (DJ) chiral perovskite materials exhibit significant promise for developing high‐performance circularly polarized light (CPL) photodetectors. However, the inherently thick nature of DJ‐phase 2D perovskite single crystal limits their ability to differentiate CPL photons with the two opposite polarization states. In addition, the growth of DJ‐phase perovskite single crystal thin films (SCTFs) has proven challenging due to the strong interlayer electronic coupling. Here, a nucleation‐controlled strategy is employed to grow a novel DJ‐phase perovskite [( R / S )‐3APr]PbI 4 [( R / S )‐3APr = ( R / S )‐3‐Aminopyrrolidine] SCTFs with large area, low thickness and hence high aspect ratios. Structural and photoluminescence analyses reveal that introducing the divalent organic cations into the perovskite framework reduce the interlayer distance, resulting in low exciton binding energy. This facilitates charge separation and transport. The resulting SCTF photodetector showcases excellent detection performance with anisotropy factor for photocurrent as high as 0.65, responsivity of 1.97 A W −1 , detectivity of 5.3 × 10 13 Jones, and 3‐dB frequency of 2940 Hz, demonstrating its potential as a promising candidate for CPL‐sensitive photodetectors. This novel approach, therefore, provides a framework for the growth of DJ‐phase perovskite SCTFs and advances their applications in sensitive CPL photodetection.