Effect of Bi Substitution on Cs3Sb2Cl9: Structural Phase Transition and Band Gap Engineering
Effect of Bi Substitution on Cs3Sb2Cl9: Structural Phase Transition and Band Gap Engineering
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DOI：
10.1021/acs.cgd.0c00171
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发表时间：
2020-05-06
影响因子：
3.8
通讯作者：
Samal, Saroj L.
中科院分区：
文献类型：
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作者：
Pradhan, Abinash;Sahoo, Subash Chandra;Samal, Saroj L.
Cs3M2X9（M = Sb，Bi；X = Cl，Br）钙钛矿被称为二维（2D）材料，以两种结构类型结晶：三角P321和正交Pnma空间群。这些含有较少毒性元素的化合物由于其固有的光伏特性而引起了巨大的研究兴趣。在本文中，我们研究了Cs3Sb2Cl9的结构稳定性以及Bi取代对上述相的结构和光学性质的影响。纯三角 Cs3Sb2Cl9 相是通过金属氯化物在 = 130 摄氏度下反应获得的。Cs3Sb2-xBixCl9 中的铋取代得到三角相和斜方相的混合物，直到 x < 0.1，进一步取代 (x >= 0.1) 得到纯斜方相。粉末 X 射线衍射和拉曼研究明确表征了相变。单晶研究证实了斜方晶系 Cs3Sb2Cl9、Cs3Sb1.94Bi0.06 Cl-9 和 Cs3Sb2Cl9 相。分别从 Cs3Sb1.94Bi0.06 Cl-9 和 Cs3Sb1.9B0.1Cl9 的单晶和 Rietveld 精修研究中，观察到 Bi 优先取代 Sb(1) 晶体位点。利用维也纳从头算模拟软件包（VASP）进行的理论研究表明，三角晶系Cs 3 Sb 2 CI 9 相均为间接带隙半导体，且其带隙均小于正交晶系Cs3Bi2Cl9。通过光学研究发现，纯斜方相 (2.86 eV) 和三角相 (2.89 eV) Cs3Sb2Cl9 的带隙处于相似的范围内，而 Bi 类似化合物斜方相 Cs3Bi2Cl9 显示出更高的带隙，为 3.0 eV。此外，通过Bi取代成功降低了三角Cs3Sb2Cl9相的带隙，并且在Cs3Sb2-xBixCl9系列中，当x = 0.1时，其带隙达到最低值2.6 eV。
Cs3M2X9 (M = Sb, Bi; X = Cl, Br) perovskites known as two-dimensional (2D) materials crystallize in two structure types, trigonal P321 and orthorhombic Pnma space groups. These compounds containing less toxic elements have generated enormous research interest due to their inherent photovoltaic properties. In this article, we have studied the structure stability of Cs3Sb2Cl9 and the effect of Bi substitution on the structure and optical properties of the above phase. The pure trigonal Cs3Sb2Cl9 phase was obtained by reacting metal chlorides at = 130 degrees C. Bismuth substitution in Cs3Sb2-xBixCl9 gives a mixture of trigonal and orthorhombic phases until x < 0.1, and further substitution (x >= 0.1) gives a pure orthorhombic phase. The phase transitions are unequivocally characterized by both powder X-ray diffraction and Raman studies. Single crystal study confirms the orthorhombic Cs3Sb2Cl9, Cs3Sb1.94Bi0.06 Cl-9, and Cs3Sb2Cl9 phases. From both single crystal and Rietveld refinement studies on Cs3Sb1.94Bi0.06 Cl-9 and Cs3Sb1.9B0.1Cl9, respectively, it is observed that Bi preferably substitutes at the Sb(1) crystallographic site. A theoretical study using the Vienna Ab initio Simulation Package (VASP) shows that both the trigonal and orthorhombic Cs 3 Sb 2 CI 9 phases are indirect band gap semiconductors, and their band gap is smaller than orthorhombic Cs3Bi2Cl9. From an optical study, it is observed that the bandgap of the pure orthorhombic (2.86 eV) and trigonal phase (2.89 eV) of Cs3Sb2Cl9 is in a similar range, while the Bi analogue compound, orthorhombic Cs3Bi2Cl9, shows a higher band gap of 3.0 eV. Further, the band gap of the trigonal Cs3Sb2Cl9 phase is successfully reduced by Bi substitution, and it goes through the lowest value of 2.6 eV for x = 0.1 in the Cs3Sb2-xBixCl9 series.