Peng Yujie, Sun Qingde, Chen Hangyan, Yin Wan-Jian
College of Energy, Soochow Institute for Energy and Materials Innovations (SIEMIS) , Soochow University , Suzhou 215006 , China.
Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies , Soochow University , Suzhou 215006 , China.
J Phys Chem Lett. 2019 Aug 15;10(16):4566-4570. doi: 10.1021/acs.jpclett.9b01657. Epub 2019 Jul 30.
Chalcogenide perovskites ABX (A = Ca, Sr, or Ba; B = Ti, Zr, or Hf; and X = O, S, or Se) have been considered as promising candidates for overcoming the stability and toxic issues of halide perovskites. In this work, we unveil the disparity of the nature of the band gap between halide and chalcogenide perovskites. First-principles calculations show that the prototype cubic phase of chalcogenide perovskites exhibits indirect band gaps with the valence band maximum and the conduction band minimum located at R and Γ points, respectively, in the Brillion zone. Therefore, the optical transitions near band edges of chalcogenide perovskites differ from those of its halide counterparts, although its stable orthorhombic phase embodies a direct band gap. We have further found that the direct-indirect band gap difference of chalcogenide perovskites in the cubic phase demonstrates a linear correlation with + μ, where and μ are the tolerance and octahedral factor, respectively, thereby providing a viable way to search chalcogenide perovskites with a quasi-direct band gap.
硫族钙钛矿ABX（A = Ca、Sr或Ba；B = Ti、Zr或Hf；X = O、S或Se）被认为是克服卤化物钙钛矿稳定性和毒性问题的有前途的候选材料。在这项工作中，我们揭示了卤化物和硫族钙钛矿之间带隙性质的差异。第一性原理计算表明，硫族钙钛矿的原型立方相表现出间接带隙，价带最大值和导带最小值分别位于布里渊区的R点和Γ点。因此，硫族钙钛矿带边附近的光学跃迁与其卤化物对应物不同，尽管其稳定的正交相体现了直接带隙。我们进一步发现，立方相硫族钙钛矿的直接-间接带隙差异与 + μ呈线性相关，其中 和μ分别是容忍度和八面体因子，从而为寻找具有准直接带隙的硫族钙钛矿提供了一种可行的方法。
