03663nas a2200133 4500008003900000245009000039210006900129260002200198520316700220100001903387700002103406700002303427856007903450 1996 d00aOptical and Electrochromic Properties of Sol-Gel Deposited Doped Tungsten Oxide Films0 aOptical and Electrochromic Properties of SolGel Deposited Doped  aBerkeleyc01/19963 a

The goal of this study is to investigate the effects of doping of tungsten oxide on its electrochromic properties. The work is directed toward the development of neutral coloring tungsten oxide materials with properties superior to undoped tungsten oxide. Two basic types of sol-gel formulations were used for experimentation. Type 1 used a WOCl4 precursor. Type 2 used a proprietary (Donnelly) tungsten complex precursor. The Type 2 precursor was used only for comparison to Type 1. Doping experiments were performed using the Type 1 chemistry. The dopants studied were Co, Cr, Nb, Ti, V and Y. The range of dopant was 1-12 mole %. Improved electrochromic behavior was observed for tungsten oxide films doped with V and Ti.

Analysis of the films included x-ray diffraction, ellipsometry, cyclic voltammetry and spectrophotometry. X-ray diffraction showed that all films heat treated at temperatures below 300°C were amorphous in structure. The refractive indices for undoped films were measured. We found the n, k values of the Type 1 films to be lower than the Type 2 films. The n and k values were n=1.79 and k=2.8x10-3, and n=2.08 and k=3.6x10-3 at 550 nm, for Type 1 and Type 2 films respectively. Both types of tungsten oxide films showed low absorption and high transparency in the visible range. As expected, we found that the film density, and hence the refractive index and extinction coefficient, depended on coating solution chemistry, hydration, and densification procedures. Undoped Type 1 films showed slightly higher lithium diffusion coefficients (DLi), compared to undoped Type 2 films, DLi=1.36x 10-9 cm2 s-1 and 1.31 x 10-9 cm2 s-1, respectively.

We also noted that the properties of the films could be reproduced for any coating chemistry and densification scheme. The electrochemical and optical behavior were determined by using an in-situ cuvette cell with a 1M LiCl04 / propylene carbonate electrolyte. Cyclic voltammetric measurements showed that doped Type 1 films exhibited electrochemical reversibility beyond 1200 cycles without change in charge capacity. A slight lowering of charge capacity was noted for the undoped films after cycling. The charge capacity for the V doped film was 16.9 mC/cm2 compared to undoped film, 9.6 mC/cm2. Spectrophotometry showed that doped films tended to exhibit a higher absorbance in their colored state compared to undoped films. Considerable improvement in the lithium diffusivity was noted for all the doped films. The greatest change was a factor of 20x for vanadium doping. Doping appeared to increase the cyclic durability of all the tungsten films out to 1200 cycles. Color changes by doping were noted for several dopants. The doped films with the best overall properties were about 8% vanadium and titanium tungsten oxide. The optimum concentration lies in the range of 7 to 12 mol%. The electrochromic color was a neutral brownish-blue for vanadium and grayish-blue for titanium doped tungsten oxide.

1 aÖzer, Nilgün1 aLampert, Carl, M1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/optical-and-electrochromic-properties02176nas a2200181 4500008004100000245005500041210005500096260001200151300001000163490000700173520164100180100002301821700002301844700001701867700001901884700002401903856006701927 1996 eng d00aOptical Indices of Lithiated Electrochromic Oxides0 aOptical Indices of Lithiated Electrochromic Oxides c07/1998 a49-570 v543 a

Optical indices have been determined for thin films of several electrochromic oxide materials. One of the most important materials in electrochromic devices, WO3, was thoroughly characterized for a range of electrochromic states by sequential injection of Li ions. Another promising material, Li0.5Ni0.5O, was also studied in detail. Less detailed results are presented for three other common lithium-intercalating electrochromic electrode materials: V2O5, LiCoO2, and CeO2-TiO2. The films were grown by sputtering, pulsed laser deposition (PLD) and sol-gel techniques. Measurements were made using a combination of variable-angle spectroscopic ellipsometry and spectroradiometry. The optical constants were then extracted using physical and spectral models appropriate to each material. Optical indices of the underlying transparent conductors, determined in separate studies, were fixed in the models of this work. The optical models frequently agree well with independent physical measurements of film structure, particularly surface roughness by atomic force microscopy. Inhomogeneity due to surface roughness, gradient composition, and phase separation are common in both the transparent conductors and electrochromics, resulting sometimes in particularly complex models for these materials. Complete sets of data are presented over the entire solar spectrum for a range of colored states. This data is suitable for prediction of additional optical properties such as oblique transmittance and design of complete electrochromic devices.

1 aRubin, Michael, D.1 avon Rottkay, Klaus1 aWen, Shi-Jie1 aÖzer, Nilgün1 aSlack, Jonathan, L. uhttps://facades.lbl.gov/publications/optical-indices-lithiated03007nas a2200217 4500008004100000245013800041210006900179260001200248300001200260490000700272520227100279653003002550653002002580653001102600653002302611653002302634100001902657700002102676700002302697856006902720 1995 eng d00aOptical and Electrochemical Characteristics of Niobium Oxide Films Prepared by Sol-Gel Process and Magnetron Sputtering: A Comparison0 aOptical and Electrochemical Characteristics of Niobium Oxide Fil c08/1996 a285-2960 v403 a

Electrochromic niobia (Nb205) coatings were prepared by the sot-gel spin-coating and d.c. magnetron sputtering techniques. Parameters were investigated for the process fabrication of sol-gel spin coated Nb205 films exhibiting high coloration efficiency comparable with that d.c. magnetron sputtered niobia films. X-ray diffraction studies (XRD) showed that the sot-gel deposited and magnetron sputtered films heat treated at temperatures below 450°C, were amorphous, whereas those heat treated at higher temperatures were slightly crystalline. X-ray photoelectron spectroscopy (XPS) studies showed that the stoichiometry of the films was Nb205. The refractive index and electrochromic coloration were found to depend on the preparation technique. Both films showed low absorption and high transparency in the visible range. We found that the n, k values of the sot-gel deposited films to be lower than for the sputtered films. The n and k values were n = 1.82 and k = 3 × 10−3, and n = 2.28 and k = 4 × 10−3 at 530 urn for sot-gel deposited and sputtered films, respectively. The electrochemical behavior and structural changes were investigated in 1 M LiC104/propylene carbonate solution. Using the electrochemical measurements and X-ray photoelectron spectroscopy, the probable electrode reaction with the lithiation and delithiation is Nb2O5 + x Li+ + x e ↔ LixNb205. Cyclic voltametric (CV) measurements showed that both Nb205 films exhibits electrochemical reversibility beyond 1200 cycles without change in performance. “In situ” optical measurement revealed that those films exhibit an electrochromic effect in the spectral range 300 < λ < 2100 nm but remain unchanged in the infrared spectral range. The change in visible transmittance was 40% for 250 nm thick electrodes. Spectroelectrochemical measurements showed that spin coated films were essentially electrochemically equivalent to those prepared by d.c. magnetron sputter deposition.

10aD.C. magnetron sputtering10aelectrochromism10aNiobia10aoptical properties10asol-gel deposition1 aÖzer, Nilgün1 aLampert, Carl, M1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/optical-and-electrochemical02070nas a2200205 4500008004100000245010400041210006900145260002700214520133500241653003201576653002201608653003101630653002601661653002301687653002301710100001901733700002001752700002101772856007101793 1995 eng d00aOptical and Electrochemical Properties of Sol-gel Spin Coated CeO2-TiO2 Films0 aOptical and Electrochemical Properties of Solgel Spin Coated CeO aSan Diego, CAc07/19953 a

The optical and electrochemical properties of sol-gel spin coated Ce02-TiO2 (50% CeO2) films were investigated for electrochrornic applications. The coating solutions were prepared by using mixed organic-inorganic | Ti(OC2H5)4 and Ce(NH4)2 (NO3)6 | precursors. X-ray diffraction studies showed the sol-gel spin-coated films were composed of an amorphous matrix of titanium oxide containing nanocrystallites of cerium oxide. The coating solar transmission value was Ts=0.8 (250 nm thick). The refractive index and the extinction coefficient were derived from transmittance measurements in the UV-VIS-NIR regions. These films had refractive index value of n=2.18 and extinction coefficient value of k=8x10-4 at λ=550 nm. Cyclic voltametric measurements showed reversible electrochemical insertion of lithium ions in a CeO2-TiO2/LiClO4-propylene carbonate electrochemical cell. During cycling the films maintain high optical transmittance. Spectrophotometric and electrochemical investigations performed on CeO2-TiO2 films revealed that these films are suitable as an optically passive counter-electrode in lithium electrochromic devices.

10acerium oxide-titanium oxide10acounter electrode10aelectrochemical properties10aelectrochromic device10aoptical properties10asol-gel deposition1 aÖzer, Nilgün1 aDeSouza, Selmar1 aLampert, Carl, M uhttps://facades.lbl.gov/publications/optical-and-electrochemical-001683nas a2200157 4500008004100000050001400041245009300055210006900148300001200217490000800229520114900237100002301386700002301409700001901432856007401451 1995 eng d aLBL-3804200aOptical Indices of the Tin-doped Indium Oxide and Tungsten Oxide Electrochromic Coatings0 aOptical Indices of the Tindoped Indium Oxide and Tungsten Oxide  a551-5560 v4033 a

Thin films of tin-doped indium oxide are widely used for transparent conductors. One application of In2O3:Sn (ITO) is transparent contacts for electrochromic electrodes. Optical design of electrochromic devices requires knowledge of the optical constants for each layer from the near ultraviolet and visible to the mid infrared. Determination of the optical constants of the electrochromic layer cannot be made in isolation; a complete device or at least a half-cell including a layer of ITO is required to change the optical state of the electrochromic material. Measurements on ITO were made using variable-angle spectral ellipsometry, and spectral transmittance and reflectance. A series of structural models were fit to this data. The problem is complicated because of inhomogeneity in the films, variability in the manufacturing process, and sensitivity to environmental conditions. The spectral dependency was modeled by a single Lorentz oscillator and a Drude free-electron component. This data was then used as the basis for a model to extract the optical constants for a tungsten oxide electrochromic film.

1 avon Rottkay, Klaus1 aRubin, Michael, D.1 aÖzer, Nilgün uhttps://facades.lbl.gov/publications/optical-indices-tin-doped-indium