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International Journal of Photoenergy
Volume 2014, Article ID 342132, 7 pages
Research Article

Electronic Structure and Optical Properties of N/Si-Codoped Anatase TiO2 Evaluated Using First Principles Calculations

1Department of Materials Science and Engineering, National United University, Miaoli 36003, Taiwan
2Department of Materials Engineering, Ming Chi University of Technology, New Taipei 24301, Taiwan
3Center for Thin Film Technologies and Applications, Ming Chi University of Technology, New Taipei 24301, Taiwan

Received 13 November 2013; Revised 9 February 2014; Accepted 3 March 2014; Published 27 April 2014

Academic Editor: Pramod H. Borse

Copyright © 2014 Huey-Jiuan Lin and Hsuan-Chung Wu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


First principles calculations were used to evaluate the electronic structure and optical properties of N/Si-monodoped and N/Si-codoped TiO2 to further understand their photocatalytic mechanisms. In accordance with the atomic distance between N and Si dopants, this study considered three N/Si codoping configurations, in which the N dopant had a tendency to bond with the Si dopant. The calculations showed that the bandgaps of the N/Si codoping models were narrow, in the range 3.01–3.05 eV, redshifting the intrinsic absorption edge. The Si 3p orbital of N/Si-codoped TiO2 plays a key role in widening the valence band (VB), thereby increasing carrier mobility. In addition, the N-induced impurity energy level in the forbidden band appears in all three N/Si codoping models, strengthening absorption in the visible region. The bandgap narrowing, VB widening, and impurity energy levels in the forbidden band are beneficial for improving the photocatalytic activity of N/Si-codoped TiO2.