A New Metal-Free Molecular Perovskite-Related Single Crystal with Quantum Wire Structure for High-Performance X-Ray Detection.

The family of metal-free molecular perovskites, an emerging novel class of eco-friendly semiconductor, welcomes a new member with a unique 1D hexagonal perovskite structure. Lowering dimensionality at molecular level is a facile strategy for crystal structure conversion, optoelectronic property regulation, and device performance optimization. Herein, the study reports the design, synthesis, packing structure, and photophysical properties of the 1D metal-free molecular perovskite-related single crystal, rac-3APD-NH4I3(rac-3APD= racemic-3-Aminopiperidinium), that features a quantum wire structure formed by infinite chains of face-sharing NH4I6 octahedra, enabling strong quantum confinement with strongly self-trapped excited (STE) states to give efficient warm orange emission with a photoluminescence quantum yield (PLQY) as high as ≈41.6%. The study accordingly unveils its photoexcited carrier dynamics: rac-3APD-NH4I3 relaxes to STE state with a short lifetime of 10 ps but decays to ground state by emitting photons with a relatively longer lifetime of 560 ps. Additionally, strong quantum confinement effect is conducive to charge transport along the octahedral channels that enables the co-planar single-crystal X-ray detectors to achieve a sensitivity as high as 1556 µC Gyair -1 cm-2. This work demonstrates the first case of photoluminescence mechanism and photophysical dynamics of 1D metal-free perovskite-related semiconductor, as well as the promise for high-performance X-ray detector.

Comparative Thermal Research on Energetic Molecular Perovskite Structures.

Molecular perovskites are promising practicable energetic materials with easy access and outstanding performances. Herein, we reported the first comparative thermal research on energetic molecular perovskite structures of (C6H14N2)[NH4(ClO4)3], (C6H14N2)[Na(ClO4)3], and (C6H14ON2)[NH4(ClO4)3] through both calculation and experimental methods with different heating rates such as 2, 5, 10, and 20 °C/min. The peak temperature of thermal decompositions of (C6H14ON2)[NH4(ClO4)3] and (C6H14N2) [Na(ClO4)3] were 384 and 354 °C at the heating rate of 10 °C/min, which are lower than that of (C6H14N2)[NH4(ClO4)3] (401 °C). The choice of organic component with larger molecular volume, as well as the replacement of ammonium cation by alkali cation weakened the cubic cage skeletons; meanwhile, corresponding kinetic parameters were calculated with thermokinetics software. The synergistic catalysis thermal decomposition mechanisms of the molecular perovskites were also investigated based on condensed-phase thermolysis/Fourier-transform infrared spectroscopy method and DSC-TG-FTIR-MS quadruple technology at different temperatures.