Structural Diversity in White-Light-Emitting Hybrid Lead Bromide Perovskites
Structural Diversity in White-Light-Emitting Hybrid Lead Bromide Perovskites
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DOI：
10.1021/jacs.8b08691
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发表时间：
2018-10-10
影响因子：
15
通讯作者：
Kanatzidis, Mercouri G.
中科院分区：
文献类型：
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作者：
Mao, Lingling;Guo, Peijun;Kanatzidis, Mercouri G.
混合有机-无机卤化物钙钛矿由于其惊人的物理性质和光电子学的前景而受到密切的研究。溴化铅和氯化铅钙钛矿表现出固有的白光发射，据信是由自陷激子（STE）引起的。在这里，我们报告了一系列新的结构多样的混合溴化铅钙钛矿，在室温下具有宽带发射。它们具有Pb/Br结构，从1D面共享结构到3D角和边共享结构。通过单晶X射线衍射和低频拉曼光谱，我们已经确定了结构中的Pb 2+的八面体环境的局部畸变水平。这些化合物的禁带宽度在2.92 ~ 3.50 eV之间，遵循“共角<共边<共面”的趋势。密度泛函理论计算表明，电子结构高度依赖于PbBr 6八面体的连接模式，其中（2，6-dmpz）（3）Pb 2Br 10的边和角共享1D结构比（hep）PbBr 3的面共享1D结构（3.10 eV）表现出更多的分散带和更小的带隙（2.49 eV）。利用光电子能谱，我们测量了这些化合物的价带的能量，发现它们几乎保持不变，而导带的能量变化。温度依赖的PL测量表明，2D和3D化合物在低温（类似于5 K）下具有较窄的PL发射，而1D化合物具有自由激子发射和STE发射。一维化合物（2，6-dmpz）（3）Pb 2Br 10具有最高的光致发光量子产率12%，这是由于其独特的结构允许有效的电荷载流子弛豫和发光。
Hybrid organic-inorganic halide perovskites are under intense investigations because of their astounding physical properties and promises for optoelectronics. Lead bromide and chloride perovskites exhibit intrinsic white-light emission believed to arise from self-trapped excitons (STEs). Here, we report a series of new structurally diverse hybrid lead bromide perovskites that have broad-band emission at room temperature. They feature Pb/Br structures which vary from 1D face sharing structures to 3D corner- and edge-sharing structures. Through single-crystal X-ray diffraction and low-frequency Raman spectroscopy, we have identified the local distortion level of the octahedral environments of Pb2+ within the structures. The band gaps of these compounds range from 2.92 to 3.50 eV, following the trend of "corner-sharing < edge-sharing < face-sharing". Density functional theory calculations suggest that the electronic structure is highly dependent on the connectivity mode of the PbBr6 octahedra, where the edge- and corner-sharing 1D structure of (2,6-dmpz)(3)Pb2Br10 exhibits more disperse bands and smaller band gap (2.49 eV) than the face-sharing 1D structure of (hep)PbBr3 (3.10 eV). Using photoemission spectroscopy, we measured the energies of the valence band of these compounds and found them to remain almost constant, while the energy of conduction bands varies. Temperature-dependent PL measurements reveal that the 2D and 3D compounds have narrower PL emission at low temperature (similar to 5 K), whereas the 1D compounds have both free exciton emission and STE emission. The 1D compound (2,6-dmpz)(3)Pb2Br10 has the highest photoluminescence quantum yield of 12%, owing to its unique structure that allows efficient charge carrier relaxation and light emission.