Printed Flexible Solid State Electrochromic Devices Based on NiO/WO3 Complementary Electrodes

In this paper, flexible solid state electrochromic devices based on NiO/WO₃ complementary electrodes and gel polyelectrolyte was successfully prepared for transmissive electrochromic applications. The cathode of WO₃ film and the anode of NiO film were prepared by inkjet printing, with gel polyelectrolyte as the Li⁺ion conductor layer. Inkjet printing is a low-cost and attractive technology for patterning electrochromic materials on various substrates and allows deposition of electrochromic materials on a specific location with simultaneous thickness control by the number of printed layers. The printing has been done on flexible transparent conductive electrodes such as indium tin oxide-(ITO) coated polyethylene terephthalate (PET), which overcomes the heavy and rigid drawbacks of ITO glass substrates. In addition, using a gel electrolyte avoids electrolyte leakage problem, allows the ease of handling reduces the cost of device packaging and attains greater reliability. The flexible device exhibits a large optical modulation, fast switching speed and high coloration efficiency.