Infrared switching electrochromic devices based on tungsten oxide

Authors

E. B. Franke, University of Nebraska-LincolnFollow
C. L. Trimble, University of Nebraska-Lincoln
J. S. Hale, J. A. Woollam Co.
Mathias Schubert, University of Nebraska-LincolnFollow
John A. Woollam, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

11-15-2000

Comments

Published in JOURNAL OF APPLIED PHYSICS, VOLUME 88, NUMBER 10, 15 NOVEMBER 2000. © 2000 American Institute of Physics. Used by permission.

Abstract

Different types of electrochromic devices for thermal emittance modulation were developed in the spectral region from mid- to far-infrared (2–40 μm). In all devices polycrystalline and amorphous tungsten oxide have been used as electrochromic and ion storage layer, respectively. Two types of all-solid-state devices were designed, one with a metal grid for the top and bottom electrode deposited on a highly emissive glass substrate, and another with a top metal grid electrode and a highly reflecting bottom metal electrode layer. Tantalum oxide is used as an ion conductor in both device types. The third device type consists of a polymeric ion conductor. All solid-state constituent layers were grown by either reactive or nonreactive dc or rf magnetron sputtering in a high vacuum environment. Modulation of the emittance is accomplished by reversible insertion of Li ions into polycrystalline WO₃ by applying and switching a small voltage across the structure. Spectrally dependent measured reflectance modulation of the device has been used to determine the device emissivity modulation with respect to the blackbody emissivity spectra at 300 K. Best device performance was found in both solid-state devices showing an emissivity modulation of about 20%.