Microstructure control of NiO-based ion storage layer with various sized NiO particles to evaluate the electrochromic performance

We have investigated the relationship between the crystalline size of the ion storage layer and the electrochromic performance. The electrochromic device was fabricated with a WO3 thin film and NiO-based ion storage layer. The electrochromic performance of the device was evaluated for various morphologies of the ion storage layer, with varying size of NiO powders using a kinetically sprayed process. The ion storage layer having the smallest crystalline size using micron-sized NiO powder, had improved initial transmittance and electrochemical reaction of electrochromic performance; this was attributed to its low charge transfer resistance and high diffusion rate of Li+ ion in the electrolyte. In particular, the electrochromic device using micron-sized NiO film exhibited an improvement of up to 65% in optical transmittance, with minimum haze. Therefore, we have proven that the electrochromic performance using the optimized microstructure of NiO ion storage layer can be improved by controlling the crystalline size of thin films deposited by the kinetically sprayed process. •Deposited NiO-based ion storage layer using kinetically spraying process.•Controlled the morphology of NiO film with various sized NiO powders.•Obtain the smallest crystalline size when using micron-sized NiO ion storage layer.•Electrochromic performance improved when using micron-sized NiO film.•High Li+ ion diffusion and low charge transfer resistance in electrolyte obtained.