Three-DimensionalHybrid Perovskitoid Single CrystalsConstructed with Di- and Monoammonium Cations for Light- Emissionand Photodetection

Hybrid lead halide perovskitoids with extended 3D connection modes have attracted a lot of attention for optoelectronic and photodetection applications, but up to now, only one example comprising divalent and monovalent cations is known, i.e., MPDA2FAPb4Br13 (MPDA = N-methylpropanediammonium, FA = formamidinium). We expand the family of mixed-cation 3D perovskitoids by introducing three analogues comprising methylammonium (MA), ethylammonium (EA), and dimethylammonium (DMA) cations in small perovskite voids. X-ray diffraction and optical studies show that these compounds adopt a monoclinic system with P2/m symmetry and are examples of 3D perovskitoids exhibiting both narrowband and broadband photoluminescence (PL) and pronounced thermochromism. Analysis of the structural and optical data revealed that the intensity of the broadband PL increases with increasing intraoctahedral distortion, mainly of the corner-sharing PbBr6octahedra. Moreover, using MPDA2MAPb4Br13, we fabricated a single-crystal-based photodetector that performs at a much lower bias voltage (0.5 V) compared to photodetectors based on other 3D perovskitoids (10 V). In addition, the device’s photocurrent remains unchanged after multiple cycles of operation under 448 nm illumination, indicating excellent stability and reliability of the photodetector. All these results not only show that a relaxed tolerance factor applies to 3D perovskitoids, paving the way for expanded structural versatility and optoelectronic tunability in this family of compounds, but also inspire further exploration of these compounds as light-emitting and photodetection materials.