Hybrid perovskites have generated a great deal of interest because of their potential in photovoltaic applications. However, the toxicity of lead means that there is interest in finding a nontoxic substitute. Bulk single crystals of both cubic CH3NH3 SnI3 and CH(NH2)2 SnI3 were obtained by using the top-seeded solution growth method under an ambient atmosphere. Structural refinement, band gap, thermal properties, and XPS measurements of CH3NH3 SnI3 and CH(NH2)2 SnI3 single crystals are also reported in detail. These results should pave the way for further applications of CH3NH3 SnI3 and CH(NH2)2 SnI3.

Environmental friendly metal halides have become emerging candidates as energy downconverting emitters for lighting and X-ray imaging applications. Herein, luminescent single crystals of tetramethylammonium manganese chloride (C 4 H 12 NMnCl 3 ) and tetraethylammonium bromide ((C 8 H 20 N) 2 MnBr 4 ) are synthesized via a facile room-temperature evaporation method. C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 with octahedrally and tetrahedrally coordinated Mn 2+ have correspondingly exhibited red and green emission peaking at 635 and 515 nm both originating from 4 T 1 -6 A 1 transition of Mn 2+ with high photoluminescence quantum yield (PLQY) of 91.8% and 85.1% benefiting from their specific crystal structures. Thanks to their strong photoexcitation under blue light, high PLQY, tunable emission spectra, good environmental stability, the white light-emitting diode based on blending of C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 delivers an outstanding luminous efficacy of 96 lm W −1 , approaching commercial level, and shows no obvious photoluminescence intensity degradation after 3000 h under operation. In addition, manganese halides also demonstrate interesting characteristics under X-ray excitation, C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 exhibit steady-state X-ray light yields of 50 500 and 24 400 photons MeV −1 , low detectable limits of 36.9 and 24.2 nGy air s −1 , good radiation hardness, and X-ray imaging demonstration with high-resolution of 5 lp mm −1 . This work presents a new avenue for luminescent Mn-based metal halides toward multifunctional light-emitting applications.

All-inorganic perovskite CsPbBr has been considered as one of the star semiconductors due to its inspiring optoelectronic properties and higher stability than the organic-inorganic hybrid counterparts. The preparation of large-size single crystals with low trap density and the performance optimization on the devices still challenge the commercial application of this material. Here the large transparent CsPbBr single crystal (ϕ 24 mm × 90 mm) was grown by a modified Bridgman method. With the determination of crystallographic directions, the anisotropic optoelectronic properties were investigated for the first time. The result shows a high electron mobility (11.61 cm/(V s)) along the b axis, one order of magnitude higher than that along the c axis. Moreover, the photoresponse measurement yields a high responsivity (5.83 A/W) and external quantum efficiency (1360%) on the (001) plane irradiated by the 532 nm laser diode with 1 mW/cm under 10 V bias, which is a 305% enhancement compared with the (010) plane. Our study on anisotropic optoelectronic properties of CsPbBr will provide a significant approach to enhance the performance of single-crystalline devices.

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Hybrid halide perovskite based solar cells have demonstrated unprecedented progress in their efficiency, leading to efficiencies of up to 22.1%, in the past six years. Moreover, their intriguing properties of high dielectric constant, wide optical absorption range, low trap density, low non-radiative recombination and photoluminescence have attracted great research interest in the fields of optoelectronic applications and photovoltaics. This review briefly outlines the frontier of the research fields of perovskite materials, and summarizes the structure and growth of hybrid perovskite single crystals. Finally, the enormous challenges and the promising outlook of these active topics are highlighted.

Chemiresistive gas sensors with low power consumption, fast response, and reliable fabrication process for a specific target gas have been now created for many applications. They require both sensitive nanomaterials and an efficient substrate chip for heating and electrical addressing. Herein, a near room working temperature and fast response triethylamine (TEA) gas sensor has been fabricated successfully by designing gold (Au)-loaded ZnO/SnO2 core-shell nanorods. ZnO nanorods grew directly on Al2O3 flat electrodes with a cost-effective hydrothermal process. By employing pulsed laser deposition (PLD) and DC-sputtering methods, the construction of Au nanoparticle-loaded ZnO/SnO2 core/shell nanorod heterostructure is highly controllable and reproducible. In comparison with pristine ZnO, SnO2, and Au-loaded ZnO, SnO2 sensors, Au-ZnO/SnO2 nanorod sensors exhibit a remarkably high and fast response to TEA gas at working temperatures as low as 40 °C. The enhanced sensing property of the Au-ZnO/SnO2 sensor is also discussed with the semiconductor depletion layer model introduced by Au-SnO2 Schottky contact and ZnO/SnO2 N-N heterojunction.

The mixed metal Pb/Sn halide perovskites have drawn significant attentions in perovskite photovoltaics due to their broad absorption spectra and tunable band gaps. To obtain a deeper understanding of these materials properties, single crystals are regarded as the best platform among various building blocks for fundamental study. Here, we report the mixed-metal MAPb x Sn1–xBr3 (MA = CH3NH3) perovskite single crystals grown by top seeded solution growth (TSSG) method. Systematical characterizations were applied to investigating their structures and optoelectronic properties. These single crystals kept higher stability even exposed to air over one month than that of MASnBr3. The outstanding electrical properties, such as lower trap-state density and higher carrier mobility, were investigated by space charge-limited current (SCLC) and the Hall Effect measurements. More importantly, these perovskite single crystals exhibited much narrower optical band gap (1.77 eV) and longer carrier lifetime (∼2 μs) than those of MAPbBr3 and MASnBr3, which showed a greatly potential application in tandem solar cells based on hybrid organic–inorganic perovskites with the optimal bandgap of 1.70–1.85 eV.

The hybrid perovskites with special optoelectronic properties have attracted more attention to the scientific and industrial applications. However, because of the toxicity and instability of lead complexes, there is interest in finding a nontoxic substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH 3 ) 3 SnX 3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites NH(CH 3 ) 3 SnX 3 (X = Cl, Br) in an ambient atmosphere by bottom-seeded solution growth (BSSG) method. More importantly, detailed structural determination and refinements, phase transition, band gap, band structure calculations, nonlinear optical (NLO) properties, XPS, thermal properties, and stability of NH(CH 3 ) 3 SnX 3 (X = Cl, Br) single crystals are demonstrated. NH(CH 3 ) 3 SnCl 3 single crystal undergoes reversible structural transformation from orthorhombic space group Cmc2 1 (no. 36) to monoclinic space group Cc (no. 9) and NH(CH 3 ) 3 SnBr 3 belongs to the orthorhombic space group Pna2 1 (no. 33) by DSC, single-crystal X-ray diffraction and temperature-dependent SHG measurements, which clarify the former results. These results should pave the way for further studies of these materials in optoelectronics.