Novel Series of Quasi-2D Ruddlesden-Popper Perovskites Based on Short-Chained Spacer Cation for Enhanced Photodetection

Quasi two-dimensional (2D) layered organic-inorganic perovskite materials (e.g., (BA)₂(MA)_n-1Pb_nI_3n+1; BA = butylamine; MA = methylamine) have recently attracted wide attention because of their superior moisture stability as compared with three-dimensional counterparts. Inevitably, hydrophobic yet insulating long-chained organic cations improve the stability at the cost of hindering charge transport, leading to the unsatisfied performance of subsequently fabricated devices. Here, we reported the synthesis of quasi-2D (iBA)₂(MA)_n-1Pb_nI_3n+1 perovskites, where the relatively pure-phase (iBA)₂PbI₄ and (iBA)₂MA₃Pb₄I₁₃ films can be obtained. Because of the shorter-branched chain of iBA as compared with that of its linear equivalent (n-butylamine, BA), the resulting (iBA)₂(MA)_n-1Pb_nI_3n+1 perovskites exhibit much enhanced photodetection properties without sacrificing their excellent stability. Through hot-casting, the optimized (iBA)₂(MA)_n-1Pb_nI_3n+1 perovskite films with n = 4 give the significantly improved crystallinity, demonstrating the high responsivity of 117.09 mA/W, large on-off ratio of 4.0 × 10², and fast response speed (rise and decay time of 16 and 15 ms, respectively). These figure-of-merits are comparable or even better than those of state-of-the-art quasi-2D perovskite-based photodetectors reported to date. Our work not only paves a practical way for future perovskite photodetector fabrication via modulation of their intrinsic material properties but also provides a direction for further performance enhancement of other perovskite optoelectronics.