Effects of defects on the electronic and optical properties of TiO2 nanosheet
Effects of defects on the electronic and optical properties of TiO2 nanosheet
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缺陷对TiO2纳米片电子和光学性能的影响
DOI：
10.1088/2516-1075/ab47ea
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发表时间：
2019-12-01
影响因子：
2.6
通讯作者：
Ma, Yuchen
中科院分区：
文献类型：
--
作者：
Jin, Fan;Zhang, Xiao;Ma, Yuchen
由于2D材料的独特性质，TiO 2纳米片在电化学和电化学储能方面的应用得到了广泛的研究。正如其对应的三维TiO 2晶体，缺陷也被认为是TiO 2纳米片的性能发挥重要作用。本文采用GW方法和Bethe-Salpeter方程（BSE）对纤蛇纹石型TiO 2（L-TiO 2）纳米片的激发态性质进行了系统的研究。结果表明，计算得到的理想纳米片的电子带隙和紫外吸收边与实验结果有很大的偏差。当存在Ti空位时，L-TiO_2的电子带隙变窄了1.1eV，计算结果与实验相符。Ti空位使L-TiO_2的激子结合能从1 eV降低到0.1eV，从而降低了光生电子和空穴的复合几率，有利于光生载流子的迁移。其他缺陷，如氧空位，对L-TiO 2的电子和光学性质没有明显的影响。我们发现，密度泛函理论（DFT）与Hubbard U修正未能预测的重要带隙变窄现象的L-TiO 2。
Due to the unique properties of 2D materials, TiO2 nanosheet has been widely studied for applications in photocatalysis and electrochemical energy storage. Just as its counterpart of the 3D TiO2 crystal, defects are also expected to play an important role in the properties of TiO2 nanosheet. In this work, by the GW method and Bethe–Salpeter equation (BSE) we systematically investigate the excited-state properties of the lepidocrocite-type TiO2 (L-TiO2) nanosheet. Our results show that the computed electronic band gap and the ultraviolet (UV) absorption edge of the perfect nanosheet deviate from the experiment greatly. When there exist Ti vacancies, the electronic band gap of L-TiO2 is narrowed by 1.1 eV, making the calculation match the experiment. Ti vacancies reduce the exciton binding energy of L-TiO2 from 1 eV to 0.1 eV, which decreases recombination probability of the photogenerated electron and hole and is beneficial for photocatalysis. Other defects, such as oxygen vacancies, do not have pronounced effect on the electronic and optical properties of L-TiO2. We find that density functional theory (DFT) with the Hubbard U correction fails to predict the important band-gap narrowing phenomenon of L-TiO2.