Reproducible high-quality perovskite single crystals by flux-regulated crystallization with a feedback loop

Controlling the linear growth rate, a critical factor that determines crystal quality, has been a challenge in solution-grown single crystals due to complex crystallization kinetics influenced by multiple parameters. Here we introduce a flux-regulated crystallization (FRC) method to directly monitor and feedback-control the linear growth rate, circumventing the need to control individual growth conditions. When applied to metal halide perovskites, the FRC maintains a stable linear growth rate for over 40 h in synthesizing CH3NH3PbBr3 and CsPbBr3 single crystals, achieving outstanding crystallinity (quantified by a full width at half-maximum of 15.3 arcsec in the X-ray rocking curve) in a centimetre-scale single crystal. The FRC is a reliable platform for synthesizing high-quality crystals essential for commercialization and systematically exploring crystallization conditions, maintaining a key parameter—the linear growth rate—constant, which enables a comprehensive understanding of the impact of other influencing factors. Controlling linear growth rate is challenging in solution-grown single crystals. Now, flux-regulated crystallization (FRC) is developed to directly feedback-control the growth rate. When applied to metal halide perovskites, FRC achieves reproducible high crystallinity, offering a platform for synthesizing high-quality single crystals and exploring crystallization conditions.