Infrared switching electrochromic devices based on tungsten oxide

Different types of electrochromic devices for thermal emittance modulation were developed in the spectral region from mid- to far-infrared (2-40 mum). In all devices polycrystalline and amorphous tungsten oxide have been used as electrochromic and ion storage layer, respectively. Two types of all-so lid-state devices were designed, one with a metal grid for the top and bott om electrode deposited on a highly emissive glass substrate, and another wi th a top metal grid electrode and a highly reflecting bottom metal electrod e layer. Tantalum oxide is used as an ion conductor in both device types. T he third device type consists of a polymeric ion conductor. All solid-state constituent layers were grown by either reactive or nonreactive dc or rf m agnetron sputtering in a high vacuum environment. Modulation of the emittan ce is accomplished by reversible insertion of Li ions into polycrystalline WO3 by applying and switching a small voltage across the structure. Spectra lly dependent measured reflectance modulation of the device has been used t o determine the device emissivity modulation with respect to the blackbody emissivity spectra at 300 K. Best device performance was found in both soli d-state devices showing an emissivity modulation of about 20%. (C) 2000 Ame rican Institute of Physics. [S0021-8979(00)01623-6].