Unraveling luminescence mechanisms in zero-dimensional halide perovskites
Unraveling luminescence mechanisms in zero-dimensional halide perovskites
复制标题
揭示零维卤化物钙钛矿的发光机制
DOI：
10.1039/c8tc01291a
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发表时间：
2018-06-28
影响因子：
6.4
通讯作者：
Du, Mao-Hua
中科院分区：
文献类型：
--
作者：
Han, Dan;Shi, Hongliang;Du, Mao-Hua
其中阴离子金属卤化物八面体（MX 6）4被有机或无机抗衡阳离子分离的零维（0 D）卤化物钙钛矿最近显示出作为优异发光材料的前景。然而，光致发光（PL）的起源，特别是在混合有机-无机和所有无机卤化物的不同的光物理性质仍然知之甚少。采用第一性原理计算方法研究了室温下具有高光致发光量子效率（PLQE）的一维有机-无机卤化物（C4 N2 H14 X）4SnX 6（X = Br，I）和在T 4 100 K时发生强烈热猝灭的一维无机卤化物Cs4 PbBr 6的激子和本征缺陷.我们发现，激子在所有三个0 D卤化物强烈绑定，不能在RT下被解除陷阱或解离，这导致不动激子在（C4 N2 H14 X）4SnX 6。然而，Cs4 PbBr 6中的激子仍然可以通过隧穿迁移，这是由激发能量的共振转移（德克斯特能量转移）实现的。Cs4 PbBr 6中激子的迁移导致了在本征缺陷处发生俘获和非辐射复合的可能性更高。我们发现，一个大的斯托克斯位移和发光中心之间的电子耦合可以忽略不计是重要的抑制激子迁移，从而提高光致发光量子效率。我们的研究结果还表明，经常观察到的明亮的绿色发射在Cs4 PbBr 6不是由于激子或缺陷诱导的发射在Cs4 PbBr 6，而是激子发射的结果，从CsPbBr 3包裹在Cs（4）PbB（r）6。
Zero-dimensional (0D) halides perovskites, in which anionic metal-halide octahedra (MX6) 4 are separated by organic or inorganic countercations, have recently shown promise as excellent luminescent materials. However, the origin of the photoluminescence (PL) and, in particular, the different photophysical properties in hybrid organic-inorganic and all inorganic halides are still poorly understood. In this work, first-principles calculations were performed to study the excitons and intrinsic defects in 0D hybrid organic-inorganic halides (C4N2H14X) 4SnX6 (X = Br, I), which exhibit a high photoluminescence quantum efficiency (PLQE) at room temperature (RT), and also in the 0D inorganic halide Cs4PbBr6, which suffers from strong thermal quenching when T 4 100 K. We show that the excitons in all three 0D halides are strongly bound and cannot be detrapped or dissociated at RT, which leads to immobile excitons in (C4N2H14X) 4SnX6. However, the excitons in Cs4PbBr6 can still migrate by tunneling, enabled by the resonant transfer of excitation energy (Dexter energy transfer). The exciton migration in Cs4PbBr6 leads to a higher probability of trapping and nonradiative recombination at the intrinsic defects. We show that a large Stokes shift and the negligible electronic coupling between luminescent centers are important for suppressing exciton migration; thereby, enhancing the photoluminescence quantum efficiency. Our results also suggest that the frequently observed bright green emission in Cs4PbBr6 is not due to the exciton or defect-induced emission in Cs4PbBr6 but rather the result of exciton emission from CsPbBr3 inclusions trapped in Cs(4)PbB(r)6.