Regulation of Quantum Wells Width Distribution in Quasi‐2D Perovskite Films for High‐Performance Photodetectors

Abstract Dynamic optimization of the quantum‐well (QW) width distribution in quasi‐2D halide perovskite thin films is an effective approach for tuning the properties of photoelectric devices. Here, that the QWs width distribution in quasi‐2D perovskite films can be controlled only by using hydroiodic acid (HI) as an additive is demonstrated. A uniform distribution of the colloidal particle size in the quasi‐2D perovskite precursor solution is achieved through the formation of soluble iodoplumbate coordination complexes, PbI₃⁻ from the reaction of HI with PbI₂, resulting in an improved phase purity in the final film. Density functional theory calculations indicate that the ideal n value quasi‐2D perovskite reaction pathway through the PbI₃⁻ complex has a lower enthalpy of formation than the random nucleation pathway without the HI additive. Benefiting from this merit, a high‐quality quasi‐2D perovskite film with optimized phase purity delivered a balanced carrier diffusion length and improved carrier mobility. The resultant photodetectors exhibited a light on/off ratio of 50 000, a responsivity of 0.96 A W⁻¹, and a detectivity of 5.7 × 10¹² Jones at 532 nm. In addition, the state‐of‐the‐art device maintained more than 80% of its initial photocurrent after 720 h of storage at 30% relative humidity.