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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]

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]

Compared with the widely reported MAPbBr 3 single crystals, formamidinium-based (FA-based) hybrid perovskites FAPbBr 3 (FPB) with superior chemical and structure stability are expected to be more efficient and perform as more reliable radiation detectors at room temperature. Here, we employ an improved inverse temperature crystallization method to grow FPB bulk single crystals, where issues associated with the retrograde solubility behavior are resolved. A crystal growth phase diagram has been proposed, and accordingly, growth parameters are optimized to avoid the formation of NH 4 Pb 2 Br 5 secondary phase. The resulting FPB crystals exhibit a high resistivity of 2.8 × 10 9 Ω·cm and high electron and hole mobility-lifetime products (μτ) of 8.0 × 10 -4 and 1.1 × 10 -3 cm 2 ·V -1 , respectively. Simultaneously, the electron and hole mobilities (μ) are evaluated to be 22.2 and 66.1 cm 2 ·V -1 ·s -1 , respectively, based on the time-of-flight technique. Furthermore, a Au/FPB SC/Au detector is constructed that demonstrates a resolvable gamma peak from 59.5 keV 241 Am γ-rays at room temperature for the first time. An energy resolution of 40.1% is obtained at 30 V by collecting the hole signals. These results demonstrate the great potential of FAPbBr 3 as a hybrid material for γ-ray spectroscopy and imaging.