Endogenous Intermediate Template Guided Crystallization for High Performance FAPbCl ₃ UV Detector

Abstract Lead‐chloride perovskite is a promising candidate for the active layer of UV detectors. However, due to the high ionic character of chloride compound, it is difficult to form a ligand‐lead adduct that guides the crystallization of perovskite, resulting in poor film quality and device performance. Herein, an endogenous intermediate template strategy is developed to guide the crystallization of lead‐chloride perovskite FAPbCl ₃ (FA = formamidine). Based on the enrichment of hydrogen bonds between ligands, a low dimensional N‐Pb‐O adduct FAPbCl ₃ ‐DMSO (DMSO = dimethyl sulfoxide) is observed in precursor liquid. This results in the endogenous formation, not the external introduction of low dimensional FA _x PbCl _y (x>1, y>3) intermediate phase, serving as a crystallization template guiding the oriented growth of FAPbCl ₃ perovskite film with large and closely packed grain. As a result, the film shows much stronger PL intensity and significantly reduced defect density. Therefore, a self‐driven lead‐chloride perovskite UV detector is realized with responsivity, detectivity and response time of 0.63 A W ⁻¹ , 1.3 × 10 ¹³ Jones, and 205/53 µs at 365 nm and zero bias. Furthermore, for the first time, a uniform 64 × 64 lead‐chloride perovskite UV array detector is successfully fabricated and achieves a promising image sensing function.