Bistable Silver Electrodeposition-Based Electrochromic Device with Reversible Three-State Optical Transformation By Using WO3 Nanoislands Modified ITO Electrode

A bistable electrochromic (EC) device which can reversibly transform between transparent, mirror, and black states based on reversible metal Ag electrodeposition is achieved by introducing 1) a (3-mercaptopropyl) trimethoxysilane (MPTMS)-treated indium-tin-oxide (ITO) glass electrode modified with WO 3 nanoislands (WNs) as the rough surface and 2) ionic liquids (IL) into electrolyte to form an anion-blocking layer, toward achieving long-term memory performance. Typically, the EC cell is packaged by sandwiching gel electrolyte between the flat and WNs-modified ITO electrodes. Under opposite voltages, this smart device can transfer from transparent to black (+2.5 V/9.4 s) or mirror (−2.5 V/8.3 s) state by depositing Ag on the WNs-modified or flat ITO electrode surface, respectively. The assembled device exhibits over 80% mirror reflectance and below 10% transmittance of black state. After power off, both the black and mirror states remain bistability for a long time (>30 min) when IL are introduced into electrolyte for the EC device. The electrical double layer in the highly viscous electrolyte with IL contributes to form a barrier to bromide ions, which protects the Ag layer from dissolution at open circuit. This multifunctional energy-efficient EC device has shown great potential and competitiveness for numerous applications compared to conventional EC devices.