AVS 46th International Symposium
    Thin Films Division Thursday Sessions
       Session TF-ThM

Paper TF-ThM9
Solid State Electrochromic Devices for Thermal Emittance Control

Thursday, October 28, 1999, 11:00 am, Room 615

Session: Nanophase Thin Films
Presenter: C.L. Trimble, University of Nebraska, Lincoln
Authors: C.L. Trimble, University of Nebraska, Lincoln
E. Franke, University of Nebraska, Lincoln
M.J. DeVries, University of Nebraska, Lincoln
J.S. Hale, J.A. Woollam Company
J.A. Woollam, University of Nebraska, Lincoln
Correspondent: Click to Email
Thin films of crystalline Li@sub x@WO@sub 3@ (0@<=@ x @<=@ 0.5) allow modulation of IR reflectance within the spectral region from 2 to 30µm depending on the amount of inserted Li ions. Weakly crystalline or amorphous NiO thin films maintain a highly IR transparent state upon Li intercalation. By changing the reflectance of the Li@sub x@WO@sub 3@ layer in contrast to the supporting device layers, electrochromic devices with variable IR emittance can be built. We study a solid state electrochromic device consisting of a five layer stack on glass substrates with a layer sequence: electrode/a-Li@sub x@NiO/Ta@sub 2@O@sub 5@/c-Li@sub x@WO@sub 3@/electrode. The layers are deposited by reactive dc and rf magnetron sputtering at various substrate temperatures, total gas pressures, and oxygen partial pressures, in high-vacuum conditions. Lithium is electrochemically inserted into WO@sub 3@ using a 1N LiClO@sub 4@/propylene carbonate solution. WO@sub 3@, NiO, and Ta@sub 2@O@sub 5@ are deposited on glass/ITO, or Si substrates. The structural and optical properties of the as-deposited thin films, as well as the Li intercalated WO@sub 3@ and NiO single layers are investigated by XRD, AFM, and IR ellipsometry, in-situ and ex-situ UV-VIS ellipsometry, and IR reflectance measurements. The WO@sub 3@, NiO, and Ta@sub 2@O@sub 5@ thin film optical constants are obtained in the IR and VIS spectral region. Electrochromic devices are designed with consideration of the single layer thin film properties. To predict the device IR emittance modulation performance IR reflection and transmission of the colored and bleached devices are measured. The device switching and memory behavior are tested. The Li depth distribution within the electrochromic devices is investigated by secondary neutral mass spectroscopy (SNMS).@footnote 1@ @FootnoteText@ @footnote 1@ Research supported by BMDO contract #DSAG60-98-C-0054 and NASA Epscor Research Center contract #NCC5-169.