Metal halide perovskites are demonstrated to show fascinating optical and electronic properties, including highly efficient luminescence, outstanding carrier transport behavior, and large light absorption coefficient. In particular, halide perovskite single crystals are characterized with superior optoelectronic performance and enhanced stability, emerging as competitive candidates for applications in solar cells, light-emitting diodes, lasers, photodetectors, and high-energy radiation detectors. Recently, remarkable advances have been achieved to grow perovskite single crystals, while there are also many challenges in the control of growth defects and further improvement of the crystal quality. Concerning these factors, recent progress of metal halide perovskite crystals from the view of crystal growth is systematically summarized. Moreover, some ongoing challenges and perspectives for halide perovskite crystals are also proposed, which will possibly provide deeper insight into the exploration of novel perovskite crystals and related devices.

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In this paper, a series of Gd1-xBixFeO3 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) nanoparticles have been readily synthesized by a green and facile sol–gel method. It gradually changed from the orthorhombic structure (space group Pbnm) to the rhombohedral perovskite structure (space group R3c). Weak ferromagnetic behavior was effectively induced by Bi3+, with reduced magnetization. It was closely related with the lattice distortion of the perovskite structure and modified interactions between Fe-O-Fe. Boosted photocatalytic activities of Gd1-xBixFeO3 were observed for the removal of methylene blue (MB) under the visible light irradiation. In particular, Gd0.5Bi0.5FeO3 showed the optimum photocatalytic efficiency, in which the degradation efficiency reached 82.1% after 180 min of visible light illumination, with good stability and repeatability. The improved performance was mainly ascribed to enhanced visible light absorption, decreased optical band gap from 2.21 to 1.8eV and stronger charge transfer efficiency. A possible photocatalytic mechanism is also proposed according to the band structure. The results indicate that this system will be a promising candidate for the degradation of organic pollutant as a novel magnetically recoverable photocatalyst.