Formamidine intercalation to broaden photoresponsive range in alternating-cations-interlayered hybrid perovskite

Two-dimensional (2D) organic-inorganic hybrid perovskites (OIHPs) have been developed as promising candidates for photodetection, owing to their excellent semiconducting features and structural tunability. However, as an important parameter for photodetection, the photoresponsive range of 2D OIHPs is usually modulated by finite metal-halide combinations, constraining their further development. The emerging aromatic amine-based alternating-cations-interlayered (A-ACI) hybrid perovskites that exhibit excellent charge transport and additional interlayered structural designability, provide an extra solution for achieving ideal photoresponsive range. Herein, for the first time, the photoresponsive range is successfully broadened in A-ACI hybrid perovskites (NMA)₄(FA)₂Pb₃Br₁₂ (2) remolding from (NMA)₄(MA)₂Pb₃Br₁₂ (1) (NMA = N-methylbenzylaminium, FA = formamidinium and MA = methylammonium). Particularly, 1 and 2 adopt an unprecedented configuration that NMA and MA/FA are alternately arranged in the interlayer in a 4:2 manner. Importantly, 2 exhibits a narrower bandgap than 1, which can be ascribed to the low-lying conduct band composed of intercalation FA π* orbitals. Meanwhile, 2 possesses a shorter interlayer distance and flatter inorganic skeleton, synergistically facilitating the wider photo-absorption range and further endowing a broadening photoresponsive range (70 nm). This research not only enriches the perovskite family but also provides insights into structure-property relationships.