Anisotropic Effects of Oxygen Vacancies on Electrochromic Properties and Conductivity of γ-Monoclinic WO3

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• 作者：Matteo Gerosa ; Cristiana Di Valentin ; Giovanni Onida ; Carlo Enrico Bottani ; Gianfranco Pacchioni
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 2, 2016
• 年：2016
• 卷：120
• 期：21
• 页码：11716-11726
• 全文大小：543K
• 年卷期：0
• ISSN：1932-7455

文摘

Tungsten trioxide (WO₃) is a paradigmatic electrochromic material, whose peculiar optical properties in the presence of oxygen vacancies or intercalated alkali atoms have been observed and investigated for a long time. In this paper we propose a rationalization of experiments based on first-principles calculations of optical and electrical properties of oxygen-deficient (reduced) WO₃. Our approach is based on a parameter-free dielectric-dependent hybrid density functional methodology, used in combination with the charge transition levels formalism, for studying excitation mechanisms in the presence of defects. Our results indicate that oxygen vacancies lead to a different physics in γ-monoclinic WO₃, depending on the orientation of the W–O–W chain where the vacancy is created, thus evidencing strong anisotropic effects rooted in the peculiar structural properties of the original nondefective monoclinic cell. Different types of oxygen vacancies can hence be classified on the basis of the calculated ground state properties, electronic structure, and excitation/emission energies, giving a satisfactory explanation to a range of experimental observations made on oxygen-deficient WO₃.