Rapid thermal annealing assisted facile solution method for tungsten-doped vanadium dioxide thin films on glass substrate

Vanadium dioxide VO₂ is an important thermochromic material with useful applications in smart energy devices. This paper describes the synthesis of high-quality vanadium dioxide thermochromic thin films directly on glass substrate without any barrier layer prepared using a simple solution method. We demonstrate that 50 nm thick VO₂ films display excellent visible transmittance (76.9% on glass, 69.4% on fused silica) and a large NIR switching efficiency (33.8% on glass, 44.3% on fused silica) at 1600 nm. It is found that the metal to semiconductor phase transition temperature T_c of undoped films can be reduced from a theoretical value of 68 °C to 49.4 °C by rapid thermal annealing. With W doping a continuous drop in the T_c is observed and for VO₂ with 2% W doping, a T_c of 25.8 °C is achieved. These good optical properties and the near room-temperature phase transition temperature suggest that solution processing with the rapid thermal annealing process is a feasible method to obtain this promising material on glass substrate for practical application in thermochromic smart windows.