Electrochromic performances of TiO2 nanocrystals thin films for smart glass applications

Electrochromic (EC) windows can adjust the visible and infrared light transmission via voltage control, providing a feasible strategy to reduce indoor energy consumption. In sol-gel spin-coated EC thin films, samples are typically subjected to a pre-heating step, also known as pre-annealing, followed by a post-deposition annealing step. Despite the extensive utilization of the sol-gel spin-coating method in EC thin film fabrication, minimal focus has been paid to the influence of the pre-heating duration on the EC properties of TiO2 thin films. While the pre-heating step incurs additional process duration and costs, the optimization of this step would result in improved fabrication process and EC performance. Therefore, this study investigated the distinct influence of the pre-heating duration on the structural, optical, and EC properties of TiO2 thin films. TiO2 nanocrystals-based EC thin films were fabricated and the pre-heating duration impact was studied in this investigation. It was found that controlling the pre-heating duration by reducing it from 60 min to 30 s resulted in more than a 3-fold enhancement in optical modulation at a wavelength of 633 nm and an enhancement of more than 1-fold in the thin film's coloration efficiency. Furthermore, it was also found that the crystalline size decreased from 17 nm to 14 nm by reducing the pre-heating time. The findings are important to elucidate the effect of the pre-heating process, especially it highlights the distinctive behaviour at shorter pre-heating durations, which is crucial in the optimization of the EC fabrication process.