Room temperature processing for solid-state electrochromic devices on single substrate: From glass to flexible plastic

• All solid-state electrochromic (EC) devices were fabricated on single substrates.
• Room-temperature processing for monolithic devices on plastic and glass.
• A suitable Nafion film was prepared as optimal electrolyte for EC applications.
• Highly transparent conductive ITO was successfully RT-deposited on solid Nafion.
• High stability and low energy absorption of devices were observed after 103 cycles.

Herein, we present, for the first time, the features of a full solid-state electrochromic (EC) device fabricated on a single substrate, made of glass as well as flexible plastic, adopting a low-cost, eco-friendly, and facile fabrication process. By combining a solution processing of Nafion electrolyte film and RF sputtering deposition at room temperature (RT) on Nafion, we obtained monolithic systems with a simplified architecture (substrate/ITO/WO3/Nafion/ITO) in which a suitable Nafion film (8 µm thick) tightly shares its interfaces with the WO3 layer and the highly transparent and conductive RF-sputtered ITO film. Compared to conventional sandwich-type EC devices using semi-solid or liquid electrolytes, the resulting devices exhibited a strong enhancement in terms of interface properties, robustness, cyclic stability, and long-term durability (at least 1000 chronoamperometric cycles). Moreover, electro-optical characterizations highlighted high transmittance modulation (49% at 650 nm), astonishing results in terms of coloration efficiency (139 cm2/C), and low energy absorption (80 mW s/cm2).

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