Additive-assisted synthesis and optoelectronic properties of (CH3NH3)4Bi6I22
Additive-assisted synthesis and optoelectronic properties of (CH3NH3)4Bi6I22
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DOI：
10.1039/c9qi01574d
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发表时间：
2020-03
影响因子：
7
通讯作者：
Manila Sharma;A. Yangui;A. Lusson;K. Boukheddaden;X. Ding;M. Du;K. Gofryk;B. Saparov
中科院分区：
文献类型：
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作者：
Manila Sharma;A. Yangui;A. Lusson;K. Boukheddaden;X. Ding;M. Du;K. Gofryk;B. Saparov
与Pb类似物相比，含有Bi和Sb的混合有机-无机卤化物通常表现出更高的稳定性和更低的毒性。本文报道了一种新的碘化铋甲基铵化合物（MA）4 Bi 6 I22（MA+ = CH 3 NH3+）的合成、晶体结构、电子结构和光学性质。有趣的是，我们发现HgI 2的存在对于（MA）4 Bi 6 I22的靶向制备是必要的。（MA）4 Bi 6 I22包含孤立的[Bi 6 I22]4−团簇，由六个共享边的八面体BiI 6单元组成，在其0 D晶体结构中被MA+阳离子分开。基于漫反射测量，估计（MA）4 Bi 6 I22的相对低的光学带隙为1.9eV。一个强烈的光致发光峰出现在636 nm，在低温下，支持指定的带隙值。电子结构计算表明，在价带和导带中存在平带，与（MA）4 Bi 6 I22的低维结构一致，并且带隙具有轻微的间接性质。我们的研究结果表明，使用的促进剂部分，如碘化汞可能会提供一种途径，以获得替代甲基碘化铋铵（MA）3Bi 2 I9。
Hybrid organic–inorganic halides containing Bi and Sb generally exhibit higher stability and lower toxicity compared to Pb analogues. In this work, the synthesis, crystal and electronic structures and optical properties of a brand-new methylammonium bismuth iodide, (MA)4Bi6I22 (MA+ = CH3NH3+), are reported. Interestingly, we find that the presence of the HgI2 is necessary for the targeted preparation of (MA)4Bi6I22. (MA)4Bi6I22 contains isolated [Bi6I22]4− clusters made of six edge-sharing octahedral BiI6 units, which are separated by MA+ cations in its 0D crystal structure. A relatively low optical band gap of 1.9 eV was estimated for (MA)4Bi6I22 based on diffuse reflectance measurements. An intense photoluminescence peak emerges at 636 nm at low temperatures that supports the assigned band gap value. Electronic structure calculations show the presence of flat bands in the valence and conduction bands, consistent with the low-dimensional structure of (MA)4Bi6I22, and slightly indirect nature of the bandgap. Our findings suggest that the use of facilitator moieties such as HgI2 may provide a pathway to obtaining alternative methylammonium bismuth iodides to (MA)3Bi2I9.