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The understanding and tailoring of crystalline defects have been important factors in the technological deployment of established semiconductors. Here, we report the secondary phase (SP) defects of CsPb2Br5 in CsPbBr3 crystals grown by inverse temperature crystallization. The micron-scale SP defects are found to possess a well-defined polyhedral morphology, illustrated by the 14-hedron model. A heterogeneous nucleation mechanism of SP defects on the step-like surface of CsPbBr3 associated with the deviation of the chemical state of the precursor solution is proposed. The spatial inhomogeneity distribution of SP defects is highlighted along the CsPbBr3 crystal growth direction. The SP defects area density at the subsurface is about 6.3%, but it exponentially decreases to 0.51% after thinning for 0.2 mm. Correspondingly, the hole mobility increases from 41.79 to 74.54 cm−2 V−1 s−1. Moreover the infrared transmittance, bulk resistivity and photoresponse ON/OFF ratio are significantly elevated. We emphasize that the lattice distortion region in the near-surface induced by the high density of SP defects severely deteriorates carrier transport due to the formed trapping centers, interface transport barrier and intrinsically poor transmission along the c axis. Therefore, understanding and eliminating SP defects is a preferred alternative for achieving high-performance CsPbBr3-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) organic–inorganic hybrid halide perovskites have recently attracted extensive attention for electronic and optoelectronic applications due to their tunable properties and superior stability compared with their three-dimensional (3D) counterparts. Here, we report two kinds of organic cation (linear butylamine (BA) and branched isobutylamine (i-BA)) tailored CsPbBr3 crystals, namely (BA)2CsPb2Br7 and (i-BA)2CsPb2Br7, grown by the temperature-cooling method. The organic cations' adjustable anisotropic structure, optoelectronic properties and X-ray detection performance have been systematically investigated. By shortening the spacer cation from BA to i-BA, the degree of anisotropy in 2D perovskite crystals is decreased, which may be ascribed to the reduced interlayer distance and barrier height resulting from the enhanced electronic coupling between neighboring organic cations. In particular, the device based on the (BA)2CsPb2Br7 crystal along the ab plane exhibits superior X-ray sensitivity up to 13.26 mC Gy−1 cm−2 at a relatively low electric field of 2.53 V mm−1, owing to the multiple quantum well structure that restricts the charge carrier transport within the ab plane resulting in efficient charge collection. Simultaneously, a superior long-term working stability is obtained under a high X-ray dose rate of 278.4 μGy s−1. We anticipate that these findings will be helpful for the development of Ruddlesden–Popper perovskites for future research and applications. [ABSTRACT FROM AUTHOR]

The "self-trap state" in low demensional halide perovskites usually induces highly efficient below-gap broadband luminescence, which makes them promising fluorescence emitting materials. However, the luminescence mechanism based on the "self-trap state" is not well understood as yet. In this work, solution-grown quasi-one-dimensional RbPbI3 crystals reveal a large Stokes shift of ∼0.57 eV, wide and strong luminescence, and a linear power-dependent luminescence, whose luminescence mechanism was attributed to the formation of a "self-trap state" in RbPbI3. Furthermore, Cs substitutional counterpart (RbxCs1−x)PbI3 crystals were found to adjust the distortions of the PbI6 octahedron and the self-trap-state-induced luminescence properties. Our work provides a new strategy to control the "self-trap-state"-induced luminescence in low demensional halide perovskite materials. [ABSTRACT FROM AUTHOR]

Herein, we report the details of the synthesis and crystal growth of a lead-free perovskite derivative Cs2TeI6 crystal, which reveals long-term environmental stability. The synthesis process is optimized to obtain pure Cs2TeI6 polycrystals, and to eliminate the formation of residual CsI resulting from high vapor pressure. Subsequently, the Cs2TeI6 single crystal with dimensions of Φ10 mm × 55 mm is grown by the vertical Bridgman method. The as-grown 0-D structural Cs2TeI6 crystal exhibits a high resistivity of 9.92 × 1011 Ω cm, and resulting mobilities of 4.03 ± 0.33 cm2 V−1 s−1 and 9.40 ± 0.45 cm2 V−1 s−1 for electrons and holes, respectively. The Au/Cs2TeI6/Au device shows a good response for optoelectronic and X-ray detection, with a relatively high X-ray sensitivity of 27.8 μC Gy−1 cm−2 and a low detection limit of 72.5 nGy s−1. [ABSTRACT FROM AUTHOR]

X-ray detection is of great significance for medical diagnostics, industrial non-destructive inspection, nuclear plants and scientific research. However, high sensitivity is needed for X-ray detectors to reduce the radiation dose applied to human bodies for the applications of medical imaging and security checks. Here, we reported sensitive X-ray detectors made of solution-grown inorganic lead perovskite CsPbBr3 single crystals and the synthesis of high-quality inorganic lead perovskite CsPbBr3 single crystals using an improved low temperature solution method, which exhibited high transmittance, mobility and mobility–lifetime products. By designing the detector in an asymmetric electrode configuration, ion migration was effectively suppressed under a high voltage with a low dark current and an outstanding photoresponse. The optimized detector exhibited high sensitivity of 1256 μC Gy−1 cm−2 for 80 kVp X-ray detection under a relatively low electric field of 20 V mm−1, which was 60 times higher than that of commercially used α-Se detectors. Due to its facile synthesis, low cost, long-term stability, and high detection sensitivity, CsPbBr3 is expected to be an outstanding candidate for commercialized sensitive X-ray detectors. [ABSTRACT FROM AUTHOR]