La掺杂氧空位的α-Bi2O3电子结构和光学性质的第一性原理研究

基于第一性原理的方法研究了本征α-Bi2O3、La掺杂、氧空位掺杂和共掺杂体系的电子结构与光学性质，以期获得性能比较优异的α-Bi2O3光催化材料。研究结果表明：掺杂后，体系结构变形较小，其中氧空位（VO）掺杂和La-VO共掺杂体系的禁带宽度价带和导带同时下移且在禁带中引入杂质能级，说明掺杂可以减小电子从价带激发到导带所需能量，有利于电子的跃迁。特别是相对于氧空位单掺杂，La-VO共掺杂使杂质能级向导带底靠近，这个倾向可能使该复合缺陷成为光生电子捕获中心的概率大于成为光生电子-空穴对复合中心的概率；同时，La-VO共掺杂导致导带底附近的能带弯曲的曲率增大即色散关系增强，从而降低了电子的有效质量，加速电子的运动，因此，La-VO共掺杂能大幅改善光生电子-空穴对的有效分离。另一方面La-VO共掺杂在显著扩展可见光吸收范围的同时，还极大地增强了可见光吸收强度。因此，La-VO共掺杂有效改善了α-Bi2O3的光催化活性。本研究为利用稀土离子掺杂改善其他光催化材料的性能提供了一个新的思路。

Abstract

Electronic structures and optical properties of intrinsic α-Bi2O3, La-doped, oxygen vacancy doped, and co-doped systems were studied by first-principles method based on density functional theory, in order to obtain α-Bi2O3 photocatalytic materials with excellent performance. The results show that the structure of the doped system is less distorted, and the oxygen vacancy (VO) doped and La-VO co-doped systems have band gaps of both valence band and conduction band shifted down and impurity energy levels introduced in band gaps, indicating that doping can reduce the energy required for electron excitation from valence band to conduction band, which is beneficial to the electron leap. In particular, the La-VO co-doping makes the impurity energy level close to conduction band bottom compared to the oxygen vacancy single doping, and this tendency may make the recombination defect more likely to be the capturing center of photogenerated electrons than the recombination center of photogenerated electron-hole pairs. At the same time, La-VO co-doping leads to the increase of the curvature of band bending near the conduction band bottom, that is, the enhancement of the dispersion relationship, which reduces the effective mass of electrons and accelerates the movement of electrons. Therefore, La-VO co-doping can greatly improve the effective separation of photogenerated electron-hole pairs. On the other hand, La-VO co-doping, while significantly extending the visible light absorption range, also greatly enhances the visible light absorption intensity. Therefore, La-VO co-doping can effectively improve the photocatalytic activity of α-Bi2O3. This study provides a new idea for improving the performance of other photocatalytic materials by using rare earth ion doping.

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熊智慧, 孔博, 李志西, 曾体贤, 帅春. La掺杂氧空位的α-Bi2O3电子结构和光学性质的第一性原理研究[J]. 人工晶体学报, 2023, 52(1): 98. XIONG Zhihui, KONG Bo, LI Zhixi, ZENG Tixian, SHUAI Chun. First-Principles Study on Electronic Structure and Optical Properties of La-Doped α-Bi2O3 with Oxygen Vacancies[J]. Journal of Synthetic Crystals, 2023, 52(1): 98.

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