Regulating 3D Phase in Quasi‐2D Perovskite Films for High‐Performance and Stable Photodetectors

The charge transport in quasi‐2D perovskites limits their applications despite the superior stability and optoelectronic properties. Herein, a novel strategy is proposed to enhance the charge transport by regulating 3D perovskite phase in quasi‐2D perovskite films. The carbohydrazide (CBH) as an additive is introduced into (PEA)(2)MA(3)Pb(4)I(13) precursors, which slows down the crystallization process and improves the phase ratio and crystal quality of the 3D phase. This structure change results in a significant improvement in charge transport and extraction, leading to the device demonstrating an almost 100% internal quantum efficiency, a peak responsivity of 0.41 A W(−1), and a detectivity of 1.31 × 10(12) Jones at 570 nm under 0 V bias. Furthermore, the air and moisture stability of (PEA)(2)MA(3)Pb(4)I(13) films is not deteriorated but gets significantly improved due to the better crystal quality and the passivation of defects by the residual CBH molecule. This work demonstrates a strategy for improving the charge transport properties of quasi‐2D perovskites and also sheds light on solving the stability issue of 3D perovskite films via the proper passivation or additives, which will inspire the fast development of the perovskite community.