Institute for Science and Applications of Molecular Ferroelectrics, Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, People's Republic of China.
Ordered Matter Science Research Center, Jiangsu Key Laboratory for Science and Applications of Molecular Ferroelectrics, Southeast University, Nanjing 211189, P. R. China.
Inorg Chem. 2023 May 15;62(19):7186-7194. doi: 10.1021/acs.inorgchem.2c04267. Epub 2023 May 2.
Hybrid lead halide perovskites have received extensive scientific attention owing to their great potential in the field of fluorescent displays and light-emitting diodes. Currently, most luminescent materials contain functional molecular and rare-earth metal ion parts. However, the mechanism of photoluminescence property in two-dimensional hybrid lead halide perovskites with different layered inorganic skeletons has been reported rarely. To better understand the effect of an inorganic skeleton on the fluorescence property, here, we report three organic-inorganic hybrid materials with different layered inorganic frameworks: (MACH)·PbBr (Prv-1, MACH = cyclohexylmethylammonium), (2-MPQ)·PbBr (Prv-2, 2-MPQ = 2-methylpiperazinium), and (TMBA)·PbBr (Prv-3, TMBA = '''-trimethylbenzylammonium). Among them, Prv-1 is a (100)-oriented perovskite, Prv-2 belongs to the (110)-oriented perovskite, and the inorganic framework of Prv-3 possesses [PbBr] units. Interestingly, Prv-1 has a strong blue-violet fluorescence emission, while the luminescence effect of Prv-2 is very weak; notably, Prv-3 emits a charming bright-orange light. Meanwhile, results of theoretical computational studies also reveal that the electronic structure of all three compounds is highly dependent on structurally distorted [PbBr] octahedra, and the frontier molecular orbital (FMO) analysis further suggests that HOMO and LUMO of Prv-3 are contributed by inorganic and organic components, respectively. In addition, all three materials belong to direct band gap semiconductors, and the band gaps are 2.79, 2.97, and 2.76 eV, respectively. Significantly, there are obvious differences in conduction bands. Based on the above analysis, the photoluminescence mechanism of three hybrid materials is explained from the electronic levels. Consequentially, this work might provide practical strategies and perspectives for exploring novel structure-related properties.
由于其在荧光显示和发光二极管领域的巨大潜力，混合卤化铅钙钛矿受到了广泛的关注。目前，大多数发光材料都包含功能分子和稀土金属离子部分。然而，具有不同层状无机骨架的二维混合卤化铅钙钛矿的光致发光特性的机制很少有报道。为了更好地理解无机骨架对荧光性质的影响，在这里，我们报道了三种具有不同层状无机骨架的有机-无机杂化材料：(MACH)·PbBr（Prv-1，MACH=环己基甲基铵）、(2-MPQ)·PbBr（Prv-2，2-MPQ=2-甲基哌嗪）和(TMBA)·PbBr（Prv-3，TMBA=三甲基苄基铵）。其中，Prv-1 是（100）取向的钙钛矿，Prv-2 属于（110）取向的钙钛矿，而 Prv-3 的无机骨架具有[PbBr]单元。有趣的是，Prv-1 具有强烈的蓝紫色荧光发射，而 Prv-2 的发光效果很弱；值得注意的是，Prv-3 发出迷人的亮橙色光。同时，理论计算研究的结果也表明，这三种化合物的电子结构高度依赖于结构畸变的[PbBr]八面体，前线分子轨道（FMO）分析进一步表明，Prv-3 的 HOMO 和 LUMO 分别由无机和有机部分贡献。此外，这三种材料都属于直接带隙半导体，带隙分别为 2.79、2.97 和 2.76eV。值得注意的是，导带之间存在明显差异。基于以上分析，从电子能级上解释了三种杂化材料的光致发光机制。因此，这项工作可能为探索新型结构相关性质提供了实际的策略和视角。
