Study of electroluminescence and photophysical properties of single halide perovskite nanocrystals

在过去的一年中，对抑制荧光闪烁的机理和方法的研究包括CsPbBr 3纳米晶体的配体工程。重点放在可重复性的合成和配体交换，以及配体的效果上的重结晶。此外，一系列的混合阳离子（MA/FA）的混合有机金属卤化物钙钛矿薄膜的制备和它们的纳米级性能进行了研究，使用PL显微光谱。在亚微米上测量的PL光谱揭示了膜的大的成分不均匀性。的不均匀性是最大的FA 50%馏分膜含有纯MA域，纯FA域，以及由不同比例的混合MA/FA阳离子的域。薄膜还显示PL闪烁，这反映了动态非辐射猝灭。淬火是最受抑制的FA 50%的薄膜，这表明真正混合MA/FA域的非辐射损失的影响最小。此外，PL闪烁与相隔几微米的位置相关，表明晶界不代表电荷传输的屏障，也不起电荷陷阱的作用，从而能够在微米距离上有效地迁移电荷。闪烁的行为也受到外部施加的电场，这另外会导致大的波动的PL光谱解释由场诱导的I-离子迁移。

In the past year, the research on the mechanism and methods of suppression of PL blinking included ligand engineering of the CsPbBr3 nanocrystals. Focus was placed on reproducibility of the nanocrystal synthesis and ligand exchange, as well as on the effect of the ligands on the nanocrystal aging. Further, a series of mixed cation (MA/FA) hybrid organo-metallic halide perovskite films were fabricated and their nanoscale properties were studied using PL microspectroscopy. PL spectra measured on sub-micrometer revealed large compositional heterogeneity of the films. The heterogeneity was largest for the FA 50% fraction films which contain purely MA domains, purely FA domains, as well as domains composed of mixed MA/FA cations of varying ratios. The films also showed PL blinking which reflects dynamic non-radiative quenching. The quenching was most suppressed for the FA 50% films which indicates that the truly mixed MA/FA domains are least affected by the non-radiative losses. Further, the PL blinking was correlated between locations that are several micrometers apart, indicating that the grain boundaries do not represent barriers for charge transport and do not work as charge traps, enabling efficient charge migration over micrometer distances. The blinking behavior was also affected by externally applied electric field, which additionally causes large fluctuations of PL spectra that are explained by field-induced I- ion migration.