Precursor concentration-tuned optical and electrochromic performance of sol-gel-derived V2O5 thin-film devices

Electrochromic (EC) devices have gained significant attention in energy-saving applications, with V 2 O 5 standing out owing to its excellent Li-ion intercalation and multi-color properties compared to the widely used WO 3 . Nonetheless, no research has addressed the effect of V 2 O 5 concentration on EC performance. Given the rising popularity of V 2 O 5 in EC devices, this observation has indicated a significant research gap that should be addressed. Therefore, this study investigated the performance of V 2 O 5 EC devices with concentrations ranging between 0.02 mol/L and 0.1 mol/L via sol-gel spin coating. Consequently, higher film thickness was observed as the sol-gel concentration increased, as the V 2 O 5 thin films transformed from amorphous to crystalline phases. Increasing grain size with worm-like structures was also observed as the concentration increased. The EC device that balanced between optical modulation (OM), coloration efficiency (CE), and coloring ( t c ) with bleaching times ( t b ) was then observed for the ITO/0.08 V 2 O 5 /electrolyte/ITO device. This device showcased optimized values for OM (37.11%), CE (26.53 cm 2 C -1 ), t c (7 s), and t b (14 s). Overall, these findings could provide novel information regarding the correlation of V 2 O 5 concentration and EC device performance. A unique contribution was also presented in this study by demonstrating a direct relationship between the concentration of sol-gel precursors, the evolution of structure, and the EC performance, potentially for large-scale production and energy-efficient smart window technologies. • Investigated V 2 O 5 EC devices with varying sol-gel concentrations. • Higher sol concentration led to crystalline films with larger grains. • Optimal EC performance achieved at 0.08 mol/L V 2 O 5 concentration. • The ITO/0.08 V 2 O 5 /electrolyte/ITO device indicated balanced OM, CE, and switching times.