@article {11626, title = {Coalescence of Nanometer Silver Islands on Oxides Grown by Filtered Cathodic Arc Deposition}, journal = {Applied Physics Letters}, volume = {82}, number = {10}, year = {2003}, pages = {1634-1636}, chapter = {1634}, abstract = {

Ultrathin silver films have been deposited on glass and oxide-coated glass using filtered cathodic arc deposition and, for comparison, magnetron sputtering. The energetic differences between these deposition methods lead to initially different film properties. Silver films made by cathodic arc deposition show an earlier onset of island coalescence, indicating a lower aspect ratio than islands produced by evaporation and sputtering. However, the as-deposited films are thermodynamically unstable, exhibiting changes on a timescale of minutes. While films of islands tend to increase their sheet resistance with time, the sheet resistance of contiguous films shows a decrease. Both effects can be explained by silver mobility driven to minimize film and interfacial energy.

}, url = {http://dx.doi.org/10.1063/1.1558955}, author = {Eungsun Byon and Thomas W.H. Oates and Andr{\'e} Anders} } @conference {11825, title = {Energy Efficient Windows in the Southern Residential Windows Market}, booktitle = {2002 ACEEE Summer Study on Energy Efficiency in Buildings}, year = {2002}, month = {08/2002}, address = {Pacific Grove, CA}, abstract = {

The greatest potential in the U.S. for cost-effective energy savings from currently available energy efficient residential windows and skylights exists in the southern market. Prindle and Arasteh recently reported that ten southern states could save over 400 million kwh and 233 MW of peak electricity generating capacity annually by adopting the International Energy Conservation Code (IECC) standard of 0.40 (or less) solar heat gain coefficient (SHGC) for new construction (Prindle \& Arasteh 2001). In 2000, Anello et al. demonstrated savings of 14.7 percent in reduced cooling load with high-performance windows (Anello et al. 2000). In 2002, Wilcox demonstrated savings of 20 percent while simulation analysis estimates cooling energy savings in the 30 percent range (Wilcox 2002).

In the southern market, there is significant opportunity for reducing cooling energy use with low solar gain low-E windows. Yet, the southern market has been slow to embrace this new technology. Market research shows that while low-E products have achieved up to 70 percent of the market share in some colder climates (Jennings, Degens \& Curtis 2002), they have gained less than 10 percent of the southern windows market (Prindle \& Arasteh 2001).

This paper will explore the residential windows market by considering the following: market barriers unique to the southern market; distribution channels in the South; the roles of utilities, codes officials, and other organizations; and other indirect factors that influence this market. This paper will profile current market transformation efforts with case studies of the Florida Windows Initiative, sponsored by the Efficient Windows Collaborative at the Alliance to Save Energy, and the Texas Windows Initiative, sponsored by the American Electric Power Company. Finally, this paper will identify the next steps that will be critical to transforming the southern residential windows market to more efficient window and skylight products.

}, author = {Alison Tribble and Kate Offringa and Bill Prindle and Dariush K. Arasteh and Jay Zarnikau and Arlene Stewart and Ken Nittler} } @article {1828, title = {Solid State Gadolinium-Magnesium Hydride Optical Switch}, journal = {Applied Physics Letters}, volume = {75}, number = {13}, year = {1999}, month = {09/1999}, pages = {1863-1865}, chapter = {1863}, abstract = {

The optical switching properties of gadolinium-magnesium hydride have been demonstrated in a solid-state electrochromic device. With positive polarization of the hydride electrode, the visible reflectance approaches 35\% with virtually zero transmission, while with negative polarization, the visible transmission exceeds 25\% at 650 nm. The switching is reversible, with intermediate optical properties between the transparent and reflecting states.

}, url = {http://dx.doi.org/10.1063/1.124853}, author = {Robert D. Armitage and Michael D. Rubin and Thomas J. Richardson and Nada O{\textquoteright}Brien and Yong Chen} } @techreport {1916, title = {Toward a Virtual Building Laboratory}, year = {1999}, month = {03/1999}, abstract = {

Buildings account for about one-third of all energy used in the US and about two-thirds of all electricity, with associated environmental impacts.(EIA 1996) After more than 20 years of DOE-supported research universities and national laboratories, a great deal is known about the energy performance of buildings and especially their components and subsystems. The development and market introduction of improved energy efficient technology, such as low-E windows and electronic ballasts, have helped reduce energy use, and the resultant savings will increase, as use of the new technologies becomes more widespread. A variety of approaches to speed market penetration have been and are being pursued, including information dissemination, research to evaluate performance and development of computer tools for making energy performance simulations available to architects and engineers at the earliest design stages. Public-domain computer building energy simulation models, (BLAST_Support_Office 1992; Winkelmann, Birdsall et al. 1993) a controversial idea 20 years ago, have been extremely successful in facilitating the design of more energy-efficient buildings and providing the technical basis for improved state building codes, federal guidelines, and voluntary standards. But the full potential of savings, estimated at 50\% of current consumption or $100 billion/year, (Bevington and Rosenfeld 1990; Todesco 1996; Holdren 1997; Kolderup and Syphers 1997; ORNL, LBNL et al. 1997) will require that architects and engineers take an integrated look at buildings beginning in the early design phase, with increasing use of sophisticated, complex and interrelated building systems. This puts a greater burden on the designer and engineer to make accurate engineering decisions.

}, author = {Joseph H. Klems and Elizabeth U. Finlayson and Thomas H. Olsen and David W Banks and Jani M. Pallis} } @article {11544, title = {Analysis of Binary Electrochromic Tungsten Oxides with Effective Medium Theory}, journal = {Thin Solid Films}, volume = {308-309}, year = {1997}, pages = {50-55}, abstract = {

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.

}, author = {Klaus von Rottkay and Nilg{\"u}n {\"O}zer and Michael D. Rubin and Thomas J. Richardson} } @techreport {1913, title = {Tips for Daylighting with Windows: The Integrated Approach}, year = {1997}, abstract = {

These guidelines provide an integrated approach to the cost-effective design of perimeter zones in new commercial buildings. They function as a quick reference for designers through a set of easy steps and rules-of-thumb, emphasizing "how-to" practical details. References are given to more detailed sources of information, should the reader wish to go further.

No guidelines can answer all possible questions from all types of users. However, this document addresses the most commonly occurring scenarios. The guidance here is limited by the medium; short paper documents can only go so far in assisting a designer with a unique project. This document has been carefully shaped to best meet the needs of a designer when time does not permit a more extensive form of assistance.

The design method used in this document emphasizes that building decisions should be made within the context of the whole building as a single functioning system rather than as an assembly of distinct parts. This integrated design approach looks at the ramifications of each individual system decision on the whole building. For example, the glazing selection will have an effect on lighting, mechanical, and interior design. Therefore, the entire design team should participate in and influence this decision{\textemdash}which typically rests with the architect alone. The benefit of an integrated design approach is a greater chance of success towards long term comfort and sustained energy savings in the building.

}, author = {Jennifer O{\textquoteright}Conner and Eleanor S. Lee and Francis M. Rubinstein and Stephen E. Selkowitz} } @techreport {58561, title = {Optical and Electrochromic Properties of Sol-Gel Deposited Doped Tungsten Oxide Films}, year = {1996}, month = {01/1996}, address = {Berkeley}, abstract = {

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{\textdegree}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.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert and Michael D. Rubin} } @article {12147, title = {Optical Indices of Lithiated Electrochromic Oxides}, journal = {Solar Energy Materials and Solar Cells}, volume = {54}, number = {4-Jan}, year = {1996}, month = {07/1998}, pages = {49-57}, chapter = {49}, abstract = {

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.

}, doi = {10.1016/S0927-0248(97)00222-5}, author = {Michael D. Rubin and Klaus von Rottkay and Shi-Jie Wen and Nilg{\"u}n {\"O}zer and Jonathan L. Slack} } @conference {1817, title = {Sol-Gel Deposited Electrochromic Films for Electrochromic Smart Window Glass}, booktitle = {International Symposium on Glass Problems, International Commission on Glass}, year = {1996}, month = {09/1996}, address = {Istanbul, Turkey}, abstract = {

Electrochrornic windows offer the ability to dynamically change the transmittance of a glazing. With the appropriate sensor and controls, this smart window can be used for energy regulation and glare control for a variety of glazing applications. The most promising are building and automotive applications. This work covers the use of sol-gel deposition processes to make active films for these windows. The sol-gel process offers a low-capital investment for the deposition of these active films. Sol-gel serves as an alternative to more expensive vacuum deposition processes. The sol-gel process utilizes solution coating followed by a hydrolysis and condensation. In this investigation we report on tungsten oxide and nickel oxide films made by the sol-gel process for electrochromic windows. The properties of the sol-gel films compare favorably to those of films made by other techniques. A typical laminated electrochromic window consists of two glass sheets coated with transparent conductors, which are coated with the active films. The two sheets are laminated together with an ionically conductive polymer. The range of visible transmission modulation of the tungsten oxide was 60\% and for the nickel oxide was 20\%. We used the device configuration of glass/SnO2:F/WO3/polymer/LizNiOxHy/SnO2:F to test the films. The nickel oxide layer had a low level of lithiation and possibly contained a small amount of water. Lithiated oxymethylene-linked poly(ethylene oxide) was used as the laminating polymer. Commercially available Sn02:F/glass (LOF-Tec glass) was used as the transparent conducting glass. We found reasonable device switching characteristics which could be used for devices.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert and Michael D. Rubin} } @article {11790, title = {Electrochemical Lithium Insertion in Sol-gel Deposited LiNbO3 Films}, journal = {Solar Energy Materials and Solar Cells}, volume = {39}, number = {4-Feb}, year = {1995}, note = {

International Meeting of Electrochromism

}, month = {12/1995}, pages = {367-375}, chapter = {367}, abstract = {

Inorganic LiNbO3 ion conducting films were prepared by sol-gel process involving two alkoxides, lithium ethoxide and niobium ethoxide. The films were analyzed by ellipsometry, X-ray diffractometry, scanning electron microscopy and impedance spectroscopy. Impedance spectroscopy indicated that the Li+ conductivity values were in the range of 6-8 x 10-7 S cm-1. The morphology and thickness of these films played an important role in the insertion of lithium ions. Spectrophotometric investigation showed that LiNbO3 films exhibit very weak cathodic coloration from 350 to 900 nm spectral region. The previous termelectrochemical and opticalnext term properties clearly indicate that sol-gel deposited LiNbO3 films can be used as lithium ion conducting layers for electrochromic device application.

}, doi = {10.1016/0927-0248(96)80002-X}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @article {12140, title = {Optical and Electrochemical Characteristics of Niobium Oxide Films Prepared by Sol-Gel Process and Magnetron Sputtering: A Comparison}, journal = {Solar Energy Materials and Solar Cells}, volume = {40}, number = {4}, year = {1995}, month = {08/1996}, pages = {285-296}, chapter = {285}, abstract = {

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{\textdegree}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 {\texttimes} 10-3, and n = 2.28 and k = 4 {\texttimes} 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. {\textquotedblleft}In situ{\textquotedblright} 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.

}, keywords = {D.C. magnetron sputtering, electrochromism, Niobia, optical properties, sol-gel deposition}, doi = {10.1016/0927-0248(95)00147-6}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert and Michael D. Rubin} } @conference {12141, title = {Optical and Electrochemical Properties of Sol-gel Spin Coated CeO2-TiO2 Films}, booktitle = {SPIE Meeting}, year = {1995}, month = {07/1995}, address = {San Diego, CA}, abstract = {

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.

}, keywords = {cerium oxide-titanium oxide, counter electrode, electrochemical properties, electrochromic device, optical properties, sol-gel deposition}, author = {Nilg{\"u}n {\"O}zer and Selmar DeSouza and Carl M Lampert} } @conference {12149, title = {Optical Indices of the Tin-doped Indium Oxide and Tungsten Oxide Electrochromic Coatings}, booktitle = {Material Research Society Symposium }, volume = {403}, year = {1995}, pages = {551-556}, abstract = {

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.

}, author = {Klaus von Rottkay and Michael D. Rubin and Nilg{\"u}n {\"O}zer} } @article {12195, title = {Preparation and Properties of Spin-Coated Nb2O5 Films by the Sol-Gel Process for Electrochemical Applications}, journal = {Thin Solid Films}, volume = {277}, number = {2-Jan}, year = {1995}, month = {05/1996}, pages = {162-168}, chapter = {162}, abstract = {

The preparation and properties of Nb2O5 coatings made by the sol-gel process were investigated. The films were deposited by spin coating on In2O3:Sn/glass and quartz substrates from a polymeric solutions of niobia derived from niobium ethoxide. The films were characterized by investigation of the stoichiometry, refractive index, optical transmission, electrochemical behavior, and the microstructure. X-ray diffraction studies showed the films to be amorphous for heat treatments below 450 {\textdegree}C. X-ray photoelectron spectroscopy (XPS) measurement revealed the O:Nb atomic stoichiometry to be 5:2. Cyclic voltammetric measurements showed that the Nb2O5/1 M LiClO4-propylene carbonate system exhibits electrochemical reversibility beyond 1200 cycles without change in performance. In situ UV-Vis-NIR spectroelectrochemical measurement revealed that Nb2O5 films exhibit an electrochromic effect in the spectral range 300\<λ\<2100 nm and remain unchanged in the infrared spectral range. The change in visible transmittance was 40\% for a 250 nm thick electrode. XPS spectra indicate that Nb(V) is reduced to a lower valence state Nb(IV) in a colored state with injected Li+. The bronze coloration is due to a simultaneous injection of electrons and Li+ ions into Nb2O5. The sol-gel-deposited\ Nb2O5 films are useful for cathodically coloring electrochromic electrodes in electrochromic devices.

}, keywords = {Electrochemistry, Niobium oxide, optical properties, X-ray photoelectron spectroscopy}, url = {http://dx.doi.org/10.1016/0040-6090(95)08011-2}, author = {Nilg{\"u}n {\"O}zer and Din-Guo Chen and Carl M Lampert} } @conference {1815, title = {Sol-Gel Deposited Amorphous Tantalum Oxide and Niobium Oxide Films as Protonic Conductors}, booktitle = {Window Innovations 95 Conference Proceedings}, year = {1995}, month = {06/1995}, address = {Toronto, Canada}, abstract = {

In this work we report on the preparation of tantalum oxide and niobium oxide films by the sol-gel method for use as proton ion conductors in electrochromic devices. Measurement of the proton conductivity was derived from impedence spectroscopy measurements. The proton conductivity for Ta2O5 and NbO5 films was 4.6 x 10-6 Scm-1 and 3.2 x 10-7 Scm-1 respectively. The structural and chemical properties of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. These films were found to be amorphous and close to the stoichometry of Ta2O5 and NbO5 respectively. In order to estimate the compatibility of these sol-gel deposited layers as ion conductors for EC devices, we investigated tantalum oxide and niobium oxide films deposited on sputtered WO3 films. Charge balance and coloration characteristics were investigated during voltammetric cycling in a pH 2 liquid electrolyte. Spectral transmittance was measured for colored and bleached conditions. The photopic weighted transmittance change and solar weighted transmittance change were Tp=35.2\% - 21.8\% and Ts=75.7\% - 14.2\% for tantala films on tungsten oxide. For niobia on tungsten oxide the values were Tp=85.3\% - 35.2\% and Ts=75.8\% - 28.1\%.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @conference {1816, title = {Sol-Gel Deposited Electrochromic Coatings}, booktitle = {Am. Optical Society, Technical Digest}, volume = {17}, year = {1995}, month = {06/1995}, pages = {344-347}, address = {Tucson, AZ}, abstract = {

Electrochromic devices have increasing application in display devices, switchable minors and smart windows. A variety of vacuum depition technologies have been used to make electrochromic devices. The sol-gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO3, V2O5, TiO2, Nb2O5 and NiOx.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @conference {1855, title = {Structural and Optical Properties of Sol-Gel Deposited Proton Conducting Ta2O5 Films}, booktitle = {8th International Workshop on Glasses and Ceramics From Gels}, year = {1995}, month = {09/1995}, address = {Faro, Portugal}, abstract = {

Proton conducting tantalum oxide films were deposited by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC2H5)5 as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400 {\textdegree}C, were amorphous. Films heat treated at higher temperatures were crystalline Ta2O5. The solar transmission values (Ts) of tantala films on glass generally range from 0.8-0.9 depending on thickness. The refractive index and the extinction coefficient were evaluated from transmittance characteristics in the UV-VIS-NIR regions. The refractive index values calculated at λ=550 nm increased from n=1.78 to 1.97 with increasing heat treatment from 150 to 450 {\textdegree}C. The films heat treated at different temperatures showed low absorption with extinction coefficients of less than k=1 x 10-3 in the visible range. Spectrophotometric and impedance spectroscopic investigations performed on Ta2O5 films revealed that these films have protonic conductivity of 3.2 x 10-6 S/cm. The films are suitable for proton conducting layers in electrochromic (EC) devices.

}, keywords = {electrochromic devices, optical proterties, proton conductor, tantalum oxide}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @article {11611, title = {Characterization of Sol-Gel Deposited Niobium Pentoxide Films for Electrochromic Devices}, journal = {Solar Energy Materials and Solar Cells}, volume = {36}, number = {4}, year = {1994}, pages = {433-443}, abstract = {

Niobium pentoxide films, fabricated by the sol-gel process, were spin coated onto conductive indium tin oxide (ITO)/glass, and microscope slides. These films were cycled in a 1M LiClO4 propylene carbonate (PC) solution, and exhibited electrochromic behavior upon the electrochemical insertion (reduction) and extraction (oxidation) of lithium. In-situ optical transmittance measurements were investigated in the ultraviolet/visible/near-infrared wavelength regions (250-2100 nm). Niobium pentoxide films showed reversible optical switching from 320 to 870 nm, but were found electrochromically inactive in the infrared region. Surface analysis using X-ray photoelectron spectroscopy (XPS) indicated little difference in the chemistry of Nb2O5 films as deposited and lithiated LixNb2O5 films, as XPS binding energies of Nb and O showed no appreciable shifts. These films were found to be amorphous by X-ray diffraction. Optical transmittance measurements combined with cyclic voltamograms and XPS spectra, revealed that the electrochromic behavior of these films occurs due to the insertion of Li+ cations into niobium pentoxide films. The bronze coloration of the niobium pentoxide films could make them useful as an electrochromic counter electrodesfor electrochromic devices.

}, author = {Nilg{\"u}n {\"O}zer and Timothy Barreto and Temel Buyuklimanl and Carl M Lampert} } @conference {11612, title = {Characterization of Tantalum Oxide Films Prepared by Sol-Gel Process for electrochemical devices}, year = {1994}, abstract = {

Tantalum oxide films were prepared by sol-gel process using tantalum ethoxide Ta(OC2H5)5. The dependence of deposition conditions (i.e. composition of polymeric solutions and spinning rate) on ionic conductivities for tantalum oxide films were studied. The best results achieved for films fabricated by the spin coating technique were from clear polymeric solutions. These films had low packing density ρ=3.2 g/cm3 and good proton conductivity (about 10-6 Ω-1 cm-1). X-ray photoelectron spectroscopy (XPS) was used for studying the compositions of the tantalum oxide films. We report on the use of tantalum oxide films as ion conductors in devices consisting of WO3/Ta2O5/H+ ion storage polymer structure. We found tantalum oxide to have very good properties for proton device applications.

}, author = {Nilg{\"u}n {\"O}zer and Yongxiang He and Carl M Lampert} } @conference {12128, title = {Office Lighting: A Review of 80 Years of Standards and Recommendations}, booktitle = {1993 IEEE Industry Applications Society Annual Meeting}, year = {1993}, month = {10/1993}, address = {Toronto, Canada}, abstract = {

This paper traces the development of quantitative office lighting standards from its beginnings to the present. It discusses the sources of recommended lighting practice, the nature of the quantitative recommendations, and trends in recommended values on a comparative basis. A critical assessment of contemporary standards is provided within this historical context.

}, author = {Werner K.E. Osterhaus} } @conference {12011, title = {Large Area Glare Sources and Their Effect on Discomfort and Visual Performance at Computer Workstations}, booktitle = {1992 IEEE Industry Applications Society Annual Meeting}, year = {1992}, month = {10/1992}, address = {Houston, TX}, abstract = {

This paper studies the effects of a large area light source of variable but uniform luminance surrounding a video display terminal (VDT) on the perceived glare discomfort and visual performance of computer operators. A set of criteria was established for rating the discomfort from glare as either intolerable, disturbing, noticeable, or imperceptible. Source luminance adjustments by means of a variable transformer to match the subjective glare criteria, as well as ratings of preselected lighting conditions on a visual analog scale with the same criteria, were used to determine comfortable lighting conditions. Results from the experiment indicate that subjects reliably selected a preferred lighting condition at any time when asked to adjust the luminance to produce optimum visual comfort. There was considerable between-subject variation in the range of luminances over which the surround field was neither noticeably too dim nor noticeably too bright. Comfortable luminance ranges also varied with initial presentation luminances immediately preceding the adjustment. Subjects preferred higher luminances following high initial presentation luminances. Performance speed at a difficult letter-counting task suggests that visual performance was slightly impaired by the presence of glare discomfort. Counting errors also occurred slightly more frequently under higher surround source luminances. There was a tendency for subjects to become more susceptible to glare over the course of the experiment.

}, author = {Werner K.E. Osterhaus and Ian L. Bailey} }