Li Xianli, Lian Xin, Pang Junhong, Luo Binbin, Xiao Yonghong, Li Ming-De, Huang Xiao-Chun, Zhang Jin Zhong
Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou, Guangdong 515063, China.
Chemistry and Chemical Engineering Guangdong Laboratory, Shantou 515063, China.
J Phys Chem Lett. 2020 Oct 1;11(19):8157-8163. doi: 10.1021/acs.jpclett.0c02355. Epub 2020 Sep 15.
Low-dimensional hybrid lead halide perovskites (LHPs) with broadband emission (BE) have been developed as promising candidates for single-source white-light-emitting diodes. However, the underlying origin of such BE is poorly understood. Herein, dual-emissive [NH(CH)NH]PbBr perovskite microsheets (PMSs) with good dispersibility are successfully prepared. Besides the general narrowband emission (NE) originating from free excitons, BE (∼522 nm) is generated under a Br-poor condition, which is not observed in the single-crystal sample. Unlike self-trapped exciton emission, the BE observed in PMSs is experimentally determined to be related to bromide vacancies (V), thereby exhibiting quasisaturation under high excitation intensity. Femtosecond transient absorption spectroscopy first shows that the trapping time of the photogenerated electrons by acceptor-like V is ∼15 ps, slower than that by surface defects (<1 ps). This study provides new insight into the underlying mechanism of BE and an effective approach to manipulating the optical properties of 2D perovskites.
具有宽带发射（BE）的低维混合铅卤化物钙钛矿（LHP）已被开发成为单源白光发光二极管的有前途的候选材料。然而，这种宽带发射的潜在起源却知之甚少。在此，成功制备了具有良好分散性的双发射[NH(CH)NH]PbBr钙钛矿微片（PMS）。除了源自自由激子的一般窄带发射（NE）外，在缺溴条件下还会产生宽带发射（~522 nm），而在单晶样品中未观察到这种现象。与自陷激子发射不同，在PMS中观察到的宽带发射经实验确定与溴空位（V）有关，因此在高激发强度下呈现准饱和状态。飞秒瞬态吸收光谱首次表明，类受体V对光生电子的俘获时间约为15 ps，比表面缺陷的俘获时间（<1 ps）要慢。这项研究为宽带发射的潜在机制提供了新的见解，并为操纵二维钙钛矿的光学性质提供了一种有效方法。
