Continuous and controllable synthesis of CsxPbyBrz-based perovskite nanocrystals by a microfluidic system

All-inorganic perovskite CsPbBr3 shows great potential in optoelectronic device applications due to their excellent optoelectrical properties. However, its practical use is still dauntingly plagued by the poor stability. Recently, its derivatives Cs4PbBr6 and CsPb2Br5 featured with good stability and the versatility in crystal structure have emerged as promising alternatives. Nevertheless, synthesizing such a series of perovskites through a facile, scalable, and high-yield method is challenging, and their luminescence mechanisms are still elusive. Herein, we reported a facile and rapid method for continuous synthesis of CsxPbyBrz-based perovskites (including Cs4PbBr6, CsPbBr3/Cs4PbBr6, CsPbBr3, CsPbBr3/CsPb2Br5, CsPb2Br5) via a microfluidic system. The transformations of different dimensional perovskite nanocrystals were realized by simply adjusting the precursor flow rate. CsPbBr3/Cs4PbBr6 and CsPbBr3/CsPb2Br5 composite nanocrystals exhibited bright emissions in their solid forms, where CsPbBr3 nanocrystals uniformly embedded in Cs4PbBr6 or CsPb2Br5 matrix. Simultaneously, strong green fluorescence exclusively from CsPbBr3 nanocrystals was detected and related energy transfer in composite nanocrystals was further investigated. Finally, the highly stable CsPbBr3/Cs4PbBr6 nanocrystals were used for the construction of WLED with a wide color gamut of 131% NTSC. This work provides a novel path for large-scale and controlled synthesis of the ternary Cs-Pb-Br materials for specific light-emitting applications.