effect transistor, [15] micro and nano oscillator, [16] sensor, [17] THz device, [18] and smart glass. [19][20][21] VO 2 thin films on glass can sense the environmental temperature, and switch the transmittance of sunlight in the infrared wavelength range at high and room temperatures, and adjust the input of solar radiation energy and indoor temperature spontaneously. Accordingly, the energy consumption in the buildings could be substantially reduced. However, there are still some obstacles to be overcome for the industrialization of VO 2 smart glass. Firstly, the phase transition temperature of VO 2 is still too high to be utilized in residence. [21] Secondly, it is difficult to achieve satisfactory luminous transmittance (T lum ) and solar modulation (ΔT sol ) at the same time. [19] Thirdly, the preparation of VO 2 thin films with good thermochromic properties is difficult: the chemical process is complex with low yield rate, while the physical methods are often carried out at high temperature. [22] A great number of strategies, such as, doping with high valence elements, [23] exerting lattice stress and strain, [24] and manufacturing oxygen vacancies, [25] and so on, have been exploited to lower the T c value. For example, the T c value can be lowered by 23 °C if VO 2 is doped with 1 at% W 6+ . [26] Mg 2+ , Ti 4+ , Sn 4+ and Zr 4+ doping can improve the T lum , but with reduced solar modulation. [27][28][29][30][31][32] Thin films prepared by colloidal lithography have the T lum value up to 70.2%, but with ΔT sol value of only 7.9%. [33] The porous thin films prepared by freeze-drying showed the better thermochromic properties with T lum of 50% and ΔT sol of 14.7%, because the filling air reduces the refractive loss. [34] However, the above methods are still complex with poor controllability. The antireflective (AR) multilayer thin films might improve the T lum of VO 2 films significantly but often degrade ΔT sol . For example, Hyun Koo et al. [35] used CeO 2 as AR film, and improved the T lum of VO 2 up to 67.5%, but with ΔT sol of only 5.4%. Liu et al. demonstrated that SnO 2 /VO 2 /SnO 2 sandwiched thin films had the T lum value of 50.2% and the ΔT sol of 15.3%. [36] However, the mechanism for the enhanced modulation by the AR films is still not well known.Herein, TiO 2 /VO 2 AR thin films are designed through optical simulations, the influences of the film stacking configuration on the T lum and ΔT sol values are discussed. Accordingly, VO 2 thin films with optimized thickness are prepared through deposition of V thin films by magnetron sputtering at room temperature and then thermal annealing in oxygen atmosphere, while TiO 2 thin films with designed thickness are prepared by VO 2 -based thin films exhibit great potential applications in thermochromic smart windows. However, it is still a challenge to synergistically achieve the high luminous transmittance (T lum ) and large solar modulation (ΔT sol ). In this paper, antireflective (AR) TiO 2 /VO 2 thin films are designed through optical simulations, and...
