Long-lived electrochromic device with multilevel bistability based on portable film-type polymer electrolytes

Abstract

Long-lived electrochromic devices (ECDs) with multilevel bistability based on a portable film-type polymer electrolyte (PFPE) were fabricated and their optical and electrical properties were characterized. WO3 and NiOx, deposited via a vacuum method, were used as electrochromic materials, and PFPEs were assembled in ECDs by a transfer method. The PFPEs were fabricated by inserting a polyvinyl acetal (PVA) based gel electrolyte between a light and a tight release films. The PFPE-based ECD operated reliably for at least 109,000 cycles and showed excellent bistability in multilevel open circuits. For 30 min after removing the applied operating voltage, the ECD maintained 90% and 99% of the original coloration and decoloration transmittance at 550 nm, respectively. The average coloration and decoloration consumed charge and efficiency over 109,000 operation cycles were 4.2 and −4.5 mC/cm2 and 81.4 and −74.8 cm2/C, respectively.