The visible transmittance and solar modulation ability of VO2 flexible foils simultaneously improved by Ti doping: an optimization and first principle studyElectronic supplementary information (ESI) available. See DOI: 10.1039/c3cp52009a

• Main Authors: Chen, Shi, Dai, Lei, Liu, Jianjun, Gao, Yanfeng, Liu, Xinling, Chen, Zhang, Zhou, Jiadong, Cao, Chuanxiang, Han, Penggang, Luo, Hongjie, Kanahira, Minoru
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp52009a

The Mott phase transition compound vanadium dioxide (VO 2 ) shows promise as a thermochromic smart material for the improvement of energy efficiency and comfort in a number of applications. However, the use of VO 2 has been restricted by its low visible transmittance ( T vis ) and limited solar modulation ability (Δ T sol ). Many efforts have been made to improve both of these limitations, but progress towards the optimization of one aspect has always come at the expense of the other. This paper reports that Ti doping results in the improvement of both the T vis and Δ T sol of VO 2 -nanoparticle-derived flexible foils to the best levels yet reported. Compared with an undoped VO 2 foil, a 15% increase (from 46.1% to 53%) in T vis and a 28% increase (from 13.4% to 17.2%) in Δ T sol are achieved at a Ti doping level of 1.1%, representing the best performance reported for similar foils or films prepared using various methods. Only a defined doping level of less than 3% is beneficial for simultaneous improvement in T vis and Δ T sol . First principle calculations suggest that an increase in the intrinsic band gap of VO 2 (M) and the reduced electron density at Fermi level of VO 2 (R) cooperate to result in the improvement of Δ T sol and that an enhancement in the optical band gap of VO 2 (M) leads to the increase of T vis . Ti doping below 3% results in the improvement of both the T vis and Δ T sol of VO 2 foils to the best levels.