Ultrafast Thermodynamic Control for Stable and Efficient Mixed Halide Perovskite Nanocrystals. (9th March 2020)

• Record Type: Journal Article
• Authors: Luo, Chao; Yan, Cheng; Li, Wen; Chun, Fengjun; Xie, Meilin; Zhu, Zhihao; Gao, Yue; Guo, Bolin; Yang, Weiqing
• Is Part Of: Advanced functional materials. Volume 30:Number 19(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-09
• Subjects: blue perovskites -- defect passivation -- mixed halides -- phase separation -- thermodynamic control; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202000026
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Low photoluminescence quantum yield (PLQY) and spectra instability, the two most difficult challenges in blue‐emitting CsPbBr x Cl3− x NCs, have not yet been solved. Quickly controlling the reaction thermodynamics is crucial to enhance crystallinity, thus PLQY and spectra stability, but it has been ignored until now. An ultrafast thermodynamic control (UTC) strategy is designed by utilizing liquid nitrogen to instantaneously freeze the superior crystal lattices of CsPbBr x Cl3− x NCs formed at high temperature. The average cooling rate exhibits a 33‐fold increase compared to conventional ice‐water cooling (from 1.5 to 50 K s −1 ). This UTC can make the reaction thermodynamic energy of the system lower than the threshold very quickly. Therefore, abrupt termination of further crystal growth can be achieved, which also avoids additional nucleation at low temperature. With the assist of defect passivation, the final blue‐emitting CsPbBr x Cl3− x NCs exhibit an absolute PLQY of 98%, representing the highest value in Pb‐based blue perovskites to date. More importantly, they exhibit superior spectra instability. This UTC strategy not only represents a new avenue to synthesize perovskite NCs with excellent crystal quality and ultrahigh PLQY, but also provides a good reference to deal with the recognized bottleneck of spectra instability. Abstract : Liquid nitrogen is employed to reduce the reaction thermodynamic energy of a halide perovskite nanocrystal system to below the threshold very quickly, thus instantaneously freezing superior crystal lattices of CsPbBr x Cl3− x NCs formed at high temperature. Crystal quality and grain size uniformity is thus improved, leading to a significant increase in luminous efficiency and spectra stability.