Enhancing visible-light transmittance while reducing phase transition temperature of VO2 by Hf–W co-doping

Abstract

In order to enhance the visible-light transmittance while reducing the insulator–metal transition (IMT) temperature, Hf–W co-doping is designed for modification of VO2. We grow high-quality HfxWyV1−x−yO2 (HfWVO2) alloy films on c-plane sapphire substrates by pulsed laser deposition, and test structural, electrical, and optical properties of the films by various techniques. The Hf–W co-doped VO2 films exhibit outstanding thermochromic performances with a high luminous transmittance up to 41.1%, a fairly good near-infrared modulation capacity of 13.1%, and a low phase transition temperature of 38.9 °C. The enhanced luminous transmittance along with reduced IMT temperature in HfWVO2 is attributed to the co-doping synergetic effect of Hf and W, which effectively improves the optical bandgap and donates extra electrons into the system, respectively, while largely retaining the near-infrared modulation capacity of VO2. Our work provides an effective strategy in tailoring VO2 toward practical smart-coating applications by Hf–W co-doping.

Quantitative 3D Temperature Rendering of Deep Tumors by a NIR-II Reversibly Responsive W-VO2@PEG Photoacoustic Nanothermometer to Promote Precise Cancer Photothermal Therapy

“…Vanadium dioxide (VO 2 ) is a thermochromic material , that is widely used in optical storage, smart windows, laser protection, and photoelectric switch fields. − Due to its relatively high phase transition temperature (∼68 °C) and poor biocompatibility, , it is normally not suitable to be used in the biological field, while after doping tungsten (W) into VO 2 with a doping concentration of ∼4%, the phase transition temperature can be successfully reduced close to the human-body-temperature range, , as indicated in Scheme . After that, the W-VO 2 nanoparticles were coated with poly­(ethylene glycol) (PEG) to enhance their dispersibility and biocompatibility.…”

Element doping: a marvelous strategy for pioneering the smart applications of VO2

“…15 Similarly, the ΔT sol of W/Nb and W/Hf co-doped VO 2 can reach 18% and 13.1%, respectively. 179,180 It is easy to find that the co-doping effect is not a simple sum of the doping effects of the individual elements, i.e., there are interactions between the doping elements. A study of W/Mo codoped VO 2 found that co-doping lowers the phase transition temperature to a greater extent than single doping at the same doping level, as shown in Fig.…”

“…15 Similarly, the Δ T sol of W/Nb and W/Hf co-doped VO 2 can reach 18% and 13.1%, respectively. 179,180 It is easy to find that the co-doping effect is not a simple sum of the doping effects of the individual elements, i.e. , there are interactions between the doping elements.…”

Thermochromic Materials for Smart Windows: A State-of-Art Review

“…As single doping can only improve one of the properties, co-doping with two elements has also been studied. By co-doping Hf and W into VO 2 , Wang et al modified the thermochromic properties of VO 2 alloy films with a T c as low as 38.9 °C, and a T lum of 41.1% (Wang et al, 2021).…”