Fabrication and Performance Evaluation of a Nanostructured ZnO-Based Solid-State Electrochromic Device

In this study, we present an all-solid-state electrochromic device (ECD) that eliminates the need for hard-to-obtain materials and conventional liquid/gel electrolytes. Using a cost-effective and industrially scalable spray coating technique, we developed an ECD containing a layer of zinc oxide nanorods (ZnO_nano) synthesized via a simple solochemical route. The device configuration includes a preformed Al-coated glass substrate, acting as a counter electrode, within a glass/Al/ZnO_nano/PEDOT:PSS architecture. The device exhibits reversible switching between light blue and dark blue states upon application of -1.2 V and +2.8 V, respectively, with a significant difference in transmittance between bleached and colored states in the visible-NIR spectrum, featuring a high coloration efficiency of 275.62 cm²/C at 600 nm. The response times required for both coloring and bleaching states were 9.92 s and 7.51 s, respectively, for a sample with an active area of 5.5 × 2.5 cm². Regarding the electrochemical stability of the ZnO-based ECD, the transmittance modulation reached around 8.01% at 600 nm after 12,800 s, following initial variations observed during the first 10 cycles. These results represent significant progress in electrochromic technology, offering a sustainable and efficient alternative to traditional ECDs. The use of economical fabrication techniques and the exclusion of critical materials highlight the potential for widespread industrial adoption of this novel ECD design.