Abstract:
The effect of 1D photonic crystals on the optical transmission of VO2 is studied by depositing thin films of VO2 nanoparticles on SiO2/TiO2 distributed Bragg reflectors (DBRs) in the near-infrared (IR) spectrum as per the earlier theoretical predictions of Rashidi et al (2018 J. Phys. D: Appl. Phys. 51 375102). Monoclinic VO2 nanoparticles with tuned crystallinity are synthesized using a facile solution processing method. Moderately crystalline (MC) and highly crystalline (HC) VO2 nanostructures are obtained by varying the synthesis temperature and post-growth annealing conditions. Both the MC VO2 and HC VO2 films exhibit the expected reduction in optical transmission in the IR region due to the structural phase transition from monoclinic (insulator) to rutile (metallic) around the critical temperature of 68 °C. By combining VO2 films on a 40% transmitting DBR structure, the average optical transmission decreases further to ~20%. The number of stacks of DBRs plays a key role in such an effective reduction of optical transmission in the IR. When the number of stacks of DBRs is further increased from 4 to 7, the optical transmission of metallic VO2 films on DBRs nearly vanishes in the near-IR spectrum in such vanadium dioxide 1D photonic crystal based composite photonic structures. Such a temperature-controlled, enhanced, broad band optical response could provide a promising design for VO2 nanoparticle based hybrid photonic absorbers for various smart window applications.