The Cs-Pb-Br system possesses excellent optical properties and unique phase transition characteristics due to soft lattice structures. Herein, a simple and green synthetic method based on self-assembly in Dimethyl formamide (DMF) is proposed to prepare CsPb2Br5 nanocrystals (NCs) with typical tetragonal structure, which exhibit orange emission and small size around 3.87 nm. Interestingly, the phase transition from CsPb2Br5 to CsPbBr3 occurs easily in DMF through mechanical induction, while the metastable mixed-phase structural CsPbBr3 NCs with an average size of about 5 nm appear and show bright yellow emission. Afterwards, in combination with the supersaturation crystallization method, stable cubic CsPbBr3 NCs with 13 nm size are obtained and display the effective green emission. The synthesized CsPb2Br5 and steady-state CsPbBr3 NCs exhibit good optical stability in solution, while the metastable CsPbBr3 NCs undergo a change in emission from yellow to green with increasing time.

中文翻译：

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CsPb2Br5 和 CsPbBr3 纳米晶的光学性能和机械诱导相变


由于软晶格结构，Cs-Pb-Br 系统具有优异的光学性能和独特的相变特性。在此，提出了一种基于二甲基甲酰胺 （DMF） 自组装的简单绿色合成方法，以制备具有典型四方结构的 CsPb2Br5 纳米晶 （NCs），其表现出橙色发射和 3.87 nm 附近的小尺寸。有趣的是，在 DMF 中，通过机械感应很容易发生从 CsPb2Br5 到 CsPbBr3 的相变，而平均尺寸约为 5 nm 的亚稳态混合相结构 CsPbBr3 NCs 出现并显示出亮黄色发射。然后，结合过饱和结晶法，获得尺寸为 13 nm 的稳定立方 CsPbBr3 NCs，并显示出有效的绿光发射。合成的 CsPb2Br5 和稳态 CsPbBr3 NCs 在溶液中表现出良好的光学稳定性，而亚稳态 CsPbBr3 NCs 随着时间的增加而从黄色变为绿色。