npj:新型直接带隙光伏材料—让懒惰的He也干点实事
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来自江苏师范大学物理与电子工程学院的石景明博士和李印威教授等人利用晶体结构预测技术(CALYPSO)与第一性原理相结合,在高压下发现氦和硅可以形成4种动力学稳定的Si2He相(oP36-Si2He,tP9-Si2He, mC18-Si2He和mC12-Si2He)。这四个相均具有主-客体结构,其中硅原子构成通道型主框架,而氦原子作为客体原子填充在通道之中。移除氦原子之后,oP36-Si2He、tP9-Si2He和mC12-Si2He中的硅框架可以保留到常压,得到3种硅的同素异形体。其中,oP36-Si2He和mC12-Si2He具有直接带隙,分别为1.24 eV和1.34 eV,接近太阳能电池应用的最佳值(~1.34 eV)。进一步研究表明,mC12-Si2He满足电偶极子跃迁允许特性并且具有比CD-Si更加优异的光吸收性能,使得其成为一种极具潜力的太阳能电池候选材料。另外,该研究表明氦是调节材料性能的优良元素,亦是合成功能材料的中间体。此研究利用氦不仅设计了具有直接带隙的光伏材料并且提出了一种寻找硅单质的同素异形体有效途径,为设计功能材料和寻找单质的同素异形体提供了理论指导。
该文近期发表于npj Computational Materials 7: 89(2021),英文标题与摘要如下,点击左下角“阅读原文”可以自由获取论文PDF。第一作者是江苏师范大学物电学院硕士研究生丁世聪,石景明博士和李印威教授为共同通讯作者。
Helium incorporation induced direct-gap silicides
Shicong Ding, Jingming Shi*, Jiahao Xie, Wenwen Cui, Pan Zhang, Kang Yang, Jian Hao, Lijun Zhang, and Yinwei Li*
The search of direct-gap Si-based semiconductors is of great interest due to the potential application in many technologically relevant fields. This work examines the incorporation of He as a possible route to form a direct band gap in Si. Structure predictions and first-principles calculations show that He and Si, at high pressure, form four dynamically stable phases of Si2He (oP36-Si2He, tP9-Si2He, mC18-Si2He, and mC12-Si2He). All phases adopt host–guest structures consisting of a channel-like Si host framework filled with He guest atoms. The Si frameworks in oP36-Si2He, tP9-Si2He, and mC12-Si2He could be retained to ambient pressure after removal of He, forming three pure Si allotropes. Among them, oP36-Si2He and mC12-Si2He exhibit direct band gaps of 1.24 and 1.34 eV, respectively, close to the optimal value (~1.3 eV) for solar cell applications. Analysis shows that mC12-Si2He with an electric dipole transition allowed band gap possesses higher absorption capacity than cubic diamond Si, which makes it to be a promising candidate material for thin-film solar cell.
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