Intermediate Phase Modulation via Bifunctional Molecular Additive for High‐Performance Quasi‐2D Perovskite Photodetectors

Abstract Quasi‐2D perovskite thin films hold great promise for creating highly efficient and stable optoelectronic devices. Regulating the intermediate phase during crystallization is crucial for determining film quality, directly impacting device performance. In this study, the bifunctional molecule L‐carnitine is introduced into the quasi‐2D precursor solution to modulate the intermediate phase during crystallization. The results demonstrate that the strong coordination between L‐carnitine and PbI 2 effectively impedes the combination of PbI 2 and dimethyl sulfoxide (DMSO), preventing the formation of the PbI 2 ·DMSO intermediate phase. This elimination of the intermediate phase mitigates the potential hazards associated with DMSO escape during subsequent annealing, significantly enhancing film quality. Furthermore, the bifunctional groups in L‐carnitine interact with the perovskite, effectively passivating film defects and enhancing thermal and illumination stability. As a result, the L‐carnitine‐modified quasi‐2D perovskite photodetector exhibits outstanding performance, with a responsivity of 2724 mA W −1 and a detectivity of 9.10 × 10 10 Jones. This research proposes a novel strategy to regulate intermediate phases during crystallization and passivate defects synergistically, enabling the production of high‐quality perovskite films and high‐performance perovskite optoelectronic devices.