Kang Byungkyun, Biswas Koushik
Department of Chemistry and Physics, Arkansas State University , State University, Arkansas 72467, United States.
J Phys Chem Lett. 2018 Feb 15;9(4):830-836. doi: 10.1021/acs.jpclett.7b03333. Epub 2018 Feb 5.
Among the important family of halide perovskites, one particular case of all-inorganic, 0-D CsPbBr and 3-D CsPbBr-based nanostructures and thin films is witnessing intense activity due to ultrafast luminescence with high quantum yield. To understand their emissive behavior, we use hybrid density functional calculations to first compare the ground-state electronic structure of the two prospective compounds. The dispersive band edges of CsPbBr do not support self-trapped carriers, which agrees with reports of weak exciton binding energy and high photocurrent. The larger gap 0-D material CsPbBr, however, reveals polaronic and excitonic features. We show that those lattice-coupled carriers are likely responsible for observed ultraviolet emission around ∼375 nm, reported in bulk CsPbBr and CsPbBr/CsPbBr composites. Ionization potential calculations and estimates of type-I band alignment support the notion of quantum confinement leading to fast, green emission from CsPbBr nanostructures embedded in CsPbBr.
在重要的卤化物钙钛矿家族中，全无机的零维CsPbBr以及基于三维CsPbBr的纳米结构和薄膜的一个特殊情况正受到广泛关注，因为它们具有超快发光且量子产率高的特性。为了理解它们的发光行为，我们使用混合密度泛函计算首先比较这两种潜在化合物的基态电子结构。CsPbBr的色散带边不支持自陷载流子，这与弱激子结合能和高光电流的报道一致。然而，带隙更大的零维材料CsPbBr显示出极化子和激子特征。我们表明，那些与晶格耦合的载流子可能是导致在块状CsPbBr和CsPbBr/CsPbBr复合材料中观察到的约375nm处紫外发射的原因。电离势计算和I型能带排列估计支持了量子限制导致嵌入CsPbBr中的CsPbBr纳米结构产生快速绿色发射的观点。
