Optical Properties Of Electrochromic Nickel Oxide Devices Utilizing A Polymeric Electrolyte

We describe the preparation and optical analysis of experimental electrochromic switching devices. These devices utilize hydrated nickel oxide as the electrochromic material, with fluorine-doped tin oxide as the counter-electrode layer and polymeric quarternary ammonium hydroxide as the electrolyte. The polymer electrolyte was synthesized from an quaternary ammonium chloride polymer by ion exchange between and OH- ions. The exchange was accomplished by using either an ion exchange resin or membrane dialysis. Voltammetric and optical measurements are compared for devices using the two polymeric electrolytes. The best device performance was achieved using the dialysis-hydroxylated polymer. We investigated the optical switching properties of devices under static and dynamic conditions. We also observed that adding lithium atoms in the nickel oxide layer improves the performance of the devices by reducing the switching time and increasing the transmittance modulation range. Our best device to date (not yet optimized) showed the integrated photopic transmittance (Tp) to be Tp(bleached)=0.70 and Tp(colored)=0.21. The corresponding solar transmittance (Ts) was Ts(bleached)=0.50, Ts(colored)=0.23. A device without the polymer electrolyte had optical properties of Ts(empty)=0.44 and Tp(empty)=0.57.