Abstract
The Heyd–Scuseria–Ernzerhof screened hybrid functional is used to investigate the strain-modulated band structure and optical properties of tetragonal WO3. An electronic bandgap of 1.53 eV for the ground state of unstrained WO3 is obtained, which is consistent with the experimental value. Upon in-plane strains of 1.36%, 3.18%, 3.37%, and 4.36% along the directions of lattice vectors a→ and b→, i.e., biaxial strains, as realized by growing WO3 on the (001) surface of LaAlO3, NdGaO3, La0.3Sr0.7Al0.65Ta0.35O3, and SrTiO3, the bandgap decreases down to 1.47 eV, 1.37 eV, 1.36 eV, and 1.30 eV, respectively. The largest change in band structure can induce the downshift of the optical absorption edge, with the optical bandgap decreasing from 2.65 eV to 2.28 eV. Further applying a strain along the direction of lattice vector c→, the bandgap can be additionally tuned very finely. Our research provides a promising tuning method for designing high efficient inorganic photovoltaic materials.
Highlights
Tungsten trioxide (WO3) is known for its various applications, including photocatalysts to decompose pollutants and waters,1 gas sensors to detect toxic gases,2 smart windows based on the electrochromism effect,3 and photoelectrochemical cells for solar energy conversion.3 The multiple properties have close relationship with its crystal structure
Thin tetragonal WO3 films have been grown on different perovskite substrates, such as LaAlO3 (LAO), NdGaO3 (NGO), La0.3Sr0.7Al0.65Ta0.35O3 (LSAT), SrTiO3 (STO), and even their heterostructures
In the present work, based on the HSE06 hybrid functional, an electronic bandgap of 1.53 eV and an optical one of 2.65 eV are obtained for tetragonal WO3, in good agreement with the experimental result7,16 and other ab initio calculations
Summary
Tungsten trioxide (WO3) is known for its various applications, including photocatalysts to decompose pollutants and waters, gas sensors to detect toxic gases, smart windows based on the electrochromism effect, and photoelectrochemical cells for solar energy conversion. The multiple properties have close relationship with its crystal structure. It is well known that the degree of distortion in most ABO3-type perovskite structures is small, since it is limited by the large ionic radius of the A-site cation. The crystal structure of WO3 can be considered as pseudoperovskite where the A-site is empty, permitting a very large distortion in WO3. Scitation.org/journal/adv great importance and necessity to investigate the effect of external strain on the electronic structures and the optical properties of tetragonal WO3. An efficient solution is using the Heyd–Scuseria– Ernzerhof screened hybrid functional (HSE06) method, which is successful in describing the bandgap of transition metal oxides, including WO3 in various phases.. In the present work, based on the HSE06 hybrid functional, an electronic bandgap of 1.53 eV and an optical one of 2.65 eV are obtained for tetragonal WO3, in good agreement with the experimental result and other ab initio calculations.. The absorption edge could move downward, with the optical bandgap decreased by 0.37 eV on STO, to permit high efficient light absorption
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