Investigation of electrochromic performances of multicolor V₂O₅ devices fabricated at low processing temperature

In recent decades, poorly insulated windows have increased the energy consumption of heating and cooling systems, thus contributing to excessive carbon dioxide emissions and other related pollution issues. From this perspective, the electrochromic (EC) windows could be a tangible solution as the indoor conditions are highly controllable by these smart devices even at a low applied voltage. Literally, vanadium pentoxide (V₂O₅) is a renowned candidate for the EC application due to its multicolor appearance and substantial lithium insertion capacity. Despite the growing interest in V₂O₅ thin films, only limited literature study is available for V₂O₅ films specifically the annealing effects of these films at lower temperatures (< 300 °C). It is noteworthy that a low temperature is advantageous for glass-based EC devices, as it prevents deformation, cracking, and structural damage to the transparent conductive glass. In this study, V₂O₅ thin films were fabricated using the sol-gel spin coating technique prior to annealing over the temperature range of 100-300 °C. Subsequently, V₂O₅ thin films were assembled into a device form to analyze their EC characteristics. The V₂O₅ device, featuring thin film annealed at 200 °C, demonstrated excellent EC performance with high optical contrast of 42.32%, high coloration efficiency (CE) of 34.93 cm²/C, as well as rapid coloring and bleaching times of 0.4 s and 3 s, respectively. These results shed light on the importance of annealing temperature control towards the EC performance of V₂O₅ devices for future applications.