Tuning the Optical Properties of Complex Oxides for Energy Applications*

Perovskites are a well-known class of materials with rich physics and a wide variety of applications. One such perovskite is tungsten oxide (WO₃), which is a well-known chromogenic material used in smart windows and other display technologies. Due to its open crystal structure, it is possible to incorporate high concentrations of dopants, making the optical properties of WO₃ highly tunable. While there have been many studies on the optical and electrical properties of WO₃, a microscopic picture of how optical absorption varies with injection of excess charge carriers is lacking.

Using state-of-the-art hybrid density functional theory calculations, we demonstrate that, in addition to alkali metals, oxygen vacancies behave as shallow donors [1]. High carrier concentrations are possible, and our results show how changes in electronic structure can drive structural changes and vice versa [2]. With a computationally tractable method based on RPA and using dense sampling meshes, we explore crystalline and disordered structures to demonstrate why these structural changes can enhance absorption at a microscopic level. Our findings shed light on how electronic features can be optimized and engineered for improved functionality in display and energy technologies.

[1] W. Wang, A. Janotti, C.G. Van de Walle. J. Mat Chem. C, 4, 6641 (2016).
[2] W. Wang, A. Janotti, C.G. Van de Walle. J. Chem. Phys., 146, 214504 (2017).