Abstract
Tungsten trioxide (WO3) is a representative electrochromic material that can change their optical properties under voltage pulse and has attracted great interest in the applications of energy efficient windows. Models of M0.125W0.875O3 and LixM0.125W0.875O3 (M=Mo, Nb, Ta, Ti, V) were built to simulate the optical properties of the bleached and colored state of WO3 materials by first-principles calculations. The results show that LixM0.125W0.875O3 (M= Nb, Ta, V) leads to an enhancement of the modulation efficiency in visible light and a decrease in the modulation efficiency in infrared (IR) region. Ti doping boosts an efficiency of the IR modulation while no modulation is observed in the visible light region. Mo doping promotes the coloration efficiency in both IR and visible regions. The predicted optical properties of these doped WO3 systems suggest the application in green house or thermal modulation smart window.
Highlights
As it is shown in pictures of density of function, the band gap results obtained from LDA and generalized gradient approximation (GGA) are 1.132 eV and 1.287 eV, respectively, compared with the experimental result 2.62 eV [35]
As the research concerns much about optical properties and it tend to compare the optical properties among several systems, the GGA method is employed in the following calculations
It is revealed that Mo doping can improve the coloration efficiency of WO3, especially in the infrared region
Summary
The alkali metal ions enter the WO3 layer (light yellow) and locate at WO6 octahedral sites (Fig. 1 (a, b)), which may result in the formation of tungsten bronze LixWO3 (blue) [2, 4]. This process is called intercalation and deintercalation process of Li+, which can be realized through a combined device with electrolyte, conducting glass, WO3 layer and a counter electrode. Dopant of a series of transition metals may result in the change in the band structure and the alteration of the spectrum, which can be implemented to modulate the electrochromic property of WO3.
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