2D Perovskite Single Crystals with Suppressed Ion Migration for High‐Performance Planar‐Type Photodetectors

2D Dion-Jacobson (DJ) perovskites have recently drawn much attention owing to their superior charge transport and high environmental stability. Unfortunately, their intrinsic optoelectronic properties are largely unexplored due to the lack of high-quality single crystals available for accurate measurements. Herein, a reactive, low-temperature-gradient crystallization process to grow high-quality 2D perovskite single crystal (BDAPbI₄ ) using symmetric straight chain 1,4-butanediammonium as a short-chain insulating spacer is developed. It is found that the BDAPbI₄ single crystal exhibits a direct bandgap with effective charge collection (μτ = 1.45 × 10^-3 cm² V^-1 ). In particular, the BDAPbI₄ single crystal shows a high ion migration activation energy (0.88 eV) that is desired for stability. Moreover, the planar-type photodetectors made of BDAPbI₄ single crystals demonstrate excellent photoresponse performance, including large dynamic linear range (150 dB), high responsivity (927 mA W^-1 ), fast response speed, and exceptional stability. Theoretical calculations reveal that the enhanced carrier transport properties are mainly attributed to the interlayer-induced coupling of the inorganic layers. Furthermore, the rigid structure of BDAPbI₄ , resulting from the strong hydrogen bonds between the organic cations and the inorganic framework, will result in both low defect density and low ion migration, leading to superior carrier transport properties and detection performance.