%0 Journal Article %J Thin Solid Films %D 1997 %T Analysis of Binary Electrochromic Tungsten Oxides with Effective Medium Theory %A Klaus von Rottkay %A Nilgün Özer %A Michael D. Rubin %A Thomas J. Richardson %X

Multicomponent oxides are of increasing interest for electrochromic electrodes. To reduce the large number of permutations in composition it would be useful to be able to predict the properties of the mixtures from the pure oxide components. WO3 mixed with V2O5 has been produced by a sol-gel technique in order to increase durability and color neutrality of conventional WO3 electrochromic coatings. Chemical composition was confirmed by Rutherford backscattering spectrometry (RBS). Surface morphology was analyzed by atomic force microscopy (AFM). Electrochromic performance of the films was tested by cyclic voltammetry with in-situ transmission control. Optical constants of vanadium tungsten oxides were determined over the whole solar spectrum. The measurements included variable angle spectroscopic ellipsometry and spectral transmittance and reflectance. An attempt is made to treat doped tungsten oxide as an effective medium consisting of a mixture of WO3 with V2O5. In the clear state, comparison of optical constants and thickness directly determined on the samples yields qualitative agreement with results from effective-medium analysis. The resulting component fraction also agrees as long as the film density does not deviate too much from the linearly interpolated value between the pure components. For the colored state, preferential trapping of electrons at one atom species hinders the application of effective medium theory.

%B Thin Solid Films %V 308-309 %P 50-55 %G eng %L LBNL-40096 %1

Windows and Daylighting Group

%2 LBNL-40096 %0 Conference Paper %B 2nd International Meeting on Electrochromism %D 1996 %T Analysis of Durability in Lithium Nickel Oxide Electrochromic Materials and Devices %A Shi-Jie Wen %A John B. Kerr %A Michael D. Rubin %A Jonathan L. Slack %A Klaus von Rottkay %X

Thin films of lithium nickel oxide were deposited by sputtering and laser ablation from targets of pressed nickel oxide and lithium oxide powders. These films were assembled into electrochromic test devices with tungsten oxide as the opposite electrode and a polymer electrolyte. Analysis of the failure modes was carried out at several levels: The composition and structure of the films were examined before and after cycling using a variety of techniques, such as infrared spectroscopy, nuclear-reaction analysis, Rutherford backscattering spectrometry, x-ray diffraction and atomic force microscopy. Absorption of water vapor was found to be a major factor determining the cyclic stability of the films. A new technique is described for incorporating reference electrodes made from an electronically isolated corner into devices. This structure enabled identification of potential problems associated with a particular interface. Finally, some of the devices were disassembled and the components examined. For example, a small quantity of the polymer was extracted and studied by gas chromatography and mass spectroscopy. Small organic fragments were discovered which correspond to expected weak points in the polymer structures.

%B 2nd International Meeting on Electrochromism %C San Diego, CA %8 10/1996 %G eng %L LBNL-39633 %1

Windows and Daylighting Group

%2 LBNL-39633