Photochemical Precharging of Tungsten Trioxide for Enhanced Transmittance Modulation in Flexible Electrochromic Devices
Lisa Brändler, Lukas Niklaus, Marco Schott, Peer Löbmann
Abstract
Abstract UV irradiation is used to precharge sputtered tungsten trioxide (WO 3 ) on polyethylene terephthalate enhancing the photochromic response with organic solvents. A comparison between the optical and electrochemical properties of photochemically and electrochemically charged WO 3 results in a correlation of the transmittance to the respective charge density. This allows for a precise control of the charge density in the precharging process monitored by UV–Vis spectroscopy. A proof‐of‐concept flexible electrochromic device combining precharged WO 3 (charge density: 20 mC cm −2 ) and Prussian blue (15 mC cm −2 ) exhibits a superior change in the visible light transmittance (τ v ) from 8% (dark) to 79% (bleached) and a coloration efficiency of 139 cm 2 C −1 at 716 nm.