@article {60938, title = {Balancing daylight, glare, and energy-efficiency goals: An evaluation of exterior coplanar shading systems using complex fenestration modeling tools}, journal = {Energy and Buildings}, volume = {112}, year = {2016}, month = {01/2016}, pages = {279-298}, abstract = {

Exterior shades are the most effective way to control solar load in buildings. Twelve different coplanar shades with different geometry, material properties and cut-off angles were investigated for two California climates: the moderate San Francisco Bay Area climate and a hot and dry Southern California climate. The presented results distinguish themselves from other simulation studies by a newly developed method that combines three research-grade software programs (Radiance, EnergyPlus and Window 7) to calculate heat transfer, daylight, and glare resulting from optically-complex fenestration systems more accurately. Simulations were run for a case with constant electric lighting and a case with daylighting controls for a prototypical, internal load dominated office building.

In the case of daylighting controls, the choice of slat angle and solar cut-off angle of a fixed exterior slat shading system is non trivial. An optimum slat angle was identified for the considered cases. Material properties (e.g., solar and visible reflectance) did not affect energy use if constant electric lighting was assumed, but they did have a significant influence on energy use intensity (EUI) when daylighting controls were assumed. Energy use increased substantially when an additional interior shade was used for glare control.

}, keywords = {Complex fenestration systems, Discomfort Glare, Energy Plus, Energy Use Intensity, Exterior shades, Glare Control, radiance}, doi = {10.1016/j.enbuild.2015.12.009}, author = {Sabine Hoffmann and Eleanor S. Lee and Andrew McNeil and Luis L. Fernandes and Dragan Vidanovic and Anothai Thanachareonkit} } @techreport {1701, title = {Optics Version 5.1.01}, year = {2002}, month = {11/2002}, institution = {Regents of the University of California}, address = {Berkeley, CA}, author = {Richard Versluis and Rebecca Powles and Michael D. Rubin} } @article {12213, title = {Refractive Index Changes of Pd-Coated Magnesium Ianthanide Switchable Mirrors Upon Hydrogen Insertion}, journal = {Journal of Applied Physics}, volume = {85}, number = {1}, year = {1999}, month = {01/1999}, pages = {408-413}, chapter = {408}, abstract = {

The optical effect upon insertion of hydrogen into Pd-coated magnesium lanthanide switchable mirrors is investigated in terms of the changes of their complex refractive indices. A significant change in the optical constants of LnMg layers is seen between the as-deposited state and the dehydrided state after one cycle. Furthermore, the optical effect of switching the Pd cap layer to a PdH cap layer was determined. It is shown that the Pd layer mainly limits the visible transmittance of the hydrided stack to about 35\%-40\%. Whereas the extinction coefficient of dehydrided LnMg layers at 550 nm is between 2.2 and 3.1, it is as low 10-4 as in the transparent state. This is of great promise to applications requiring large optical contrast (e.g., optical switches).

}, issn = {0021-8979 }, doi = {10.1063/1.369399}, author = {Klaus von Rottkay and Michael D. Rubin and Peter A. Duine} } @article {11766, title = {Effect of Hydrogen Insertion on the Optical Properties of PD-Coated Magnesium Lanthanides}, journal = {Electrochimica Acta}, year = {1998}, month = {9/1998}, address = {London, U.K.}, abstract = {

Metallic magnesium lanthanide thin films upon insertion of hydrogen transform to a highly transparent hydride phase. With a Pd overlayer, the transformation can be produced either by electrochemical insertion of hydrogen or by exposing the film to hydrogen gas. Unlike amorphous oxide electrochromics, the transformation is accompanied by a large change in visible reflectance (about 50\%). The optical switching effect in these materials is investigated in terms of changes in the complex refractive index as determined by variable-angle spectroscopic ellipsometric and normal-incidence radiometric measurements over the solar spectrum. Furthermore the optical effect of converting the Pd caplayer to Pd-H was determined. It is shown that the pd layer limits the visible transmittance of the hyrdrided stack to about 35-40\%. Whereas the extinction coefficient of the dehydrided LnMg-layers at 550 nm is between 2.2 and 3.1, it is as low as 10-4 in the transparent state.

}, author = {Klaus von Rottkay and Michael D. Rubin and Franck Michalak and Robert D. Armitage and Thomas J. Richardson and Jonathan L. Slack and Peter A. Duine} } @article {11792, title = {Electrochromic lithium nickel oxide by pulsed laser deposition and sputtering}, journal = {Solar Energy Materials and Solar Cells}, volume = {54}, number = {4-Jan}, year = {1998}, month = {07/1998}, pages = {59-66}, chapter = {59}, abstract = {

Thin films of lithium nickel oxide were deposited by sputtering and pulsed laser deposition (PLD) from targets of pressed LiNiO2 powder. The composition and structure of these films were analyzed using a variety of techniques, such as nuclear-reaction analysis, Rutherford backscattering spectrometry (RBS), X-ray diffraction, infrared spectroscopy, and atomic-force microscopy. Crystalline structure, surface morphology and chemical composition of LixNi1-xO thin films depend strongly on deposition oxygen pressure, temperature as well as substrate{\textendash}target distance. The films produced at temperatures lower than 600{\textdegree}C spontaneously absorb CO2 and H2O at their surface once they are exposed to the air. The films deposited at 600{\textdegree}C proved to be stable in air over a long period. Even at room temperature the PLD films are denser and more stable than sputtered films. RBS determined the composition of the best films to be Li0.5Ni0.5O deposited by PLD at 60\ mTorr O2 pressure. Electrochemical tests show that the films exhibit excellent reversibility in the range 1.0{\textendash}3.4\ V versus lithium. Electrochemical formatting which is used to develop electrochromism in other films is not needed for the stoichiometric films. The optical transmission range is almost 70\% at 550\ nm for 150\ nm-thick films. Devices made from these films were analyzed using novel reference electrodes and by disassembling after cycling.

}, keywords = {Lithium nickel oxide, pulsed laser deposition, sputtering}, doi = {10.1016/S0927-0248(97)00223-7}, author = {Michael D. Rubin and Shi-Jie Wen and Thomas J. Richardson and John B. Kerr and Klaus von Rottkay and Jonathan L. Slack} } @article {11794, title = {Electrochromic Lithium Nickel Oxide Thin Films by RF-Sputtering from a LiNiO2 Target}, journal = {Electrochimica Acta}, volume = {44}, number = {18}, year = {1998}, pages = {3085-3092}, abstract = {

Thin films of lithium nickel oxide were deposited by rf sputtering from a stoichiometric LiNiO2 target. The composition and structure of these films depended on the oxygen pressure during deposition (sputtering gas is Argon), and, to a certain extent, the target history. The sputtering geometry, i.e. the substrate to target distance and the sputtering angle were also critical. the films exhibit excellent reversibility in the potential range 1.1V to 3.8 V vs Li/Li+ and could be cycled in a liquid electrolyte half cell for more than 3000 cycles with a switching range ΔTvis close to 70\%. The coloration efficiency in the visible was typically -30 to -40 cm2 C-1. The switching performance of a device utilizing a lithium nickel oxide film as counter electrode for a tungsten oxide electrochromic film is reported.

}, author = {Franck Michalak and Klaus von Rottkay and Thomas J. Richardson and Jonathan L. Slack and Michael D. Rubin} } @article {11805, title = {Ellipsometry on Sputter Deposited Tin Oxide Films: Optical Constants Versus Stoichiometry Hydrogen Content, and Amount of Electrochemically Intercalated Lithium}, journal = {Applied Optics}, volume = {37}, number = {31}, year = {1998}, pages = {7734-7741}, abstract = {

Tin oxide thin films were deposited by reactive radio-frequency magnetron sputtering onto In2O3:Sn coated and bare glass substrates. Optical constants in the 300-2500 nm wavelength range were determined by a combination of variable-angle spectroscopic ellipsometry and spectrophotometric transmittance measurements. Surface roughness was modeled from optical measurements and compared with atomic-force microscopy. The two techniques gave consistent results. The fit between experimental optical data and model results could be significantly improved when it was assumed that the refractive index of the Sn oxide varied across the film thickness. Varying the oxygen partial pressure during deposition made it possible to obtain films whose complex refractive index changed at the transition from SnO to SnO2. An addition of hydrogen gas during sputtering led to lower optical constants in the full spectral range in connection with a blue shift of the band gap. Electrochemical intercalation of lithium ions into the Sn oxide films raised their refractive index and enhanced their refractive-index gradient.

}, author = {Jan Isidorsson and Claes G. Granqvist and Klaus von Rottkay and Michael D. Rubin} } @conference {2929, title = {Integrated Performance of an Automated Venetian Blind/Electric Lighting System in a Full-Scale Private Office}, booktitle = {ASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII}, year = {1998}, month = {09/1998}, address = {Clearwater Beach, FL}, abstract = {

Comprehensive results are presented from a full-scale testbed of a prototype automated venetian blind/lighting system installed in two unoccupied, private offices in Oakland, California. The dynamic system balanced daylight against solar heat gains in real-time, to reduce perimeter zone energy use and to increase comfort. This limited proof-of-concept test was designed to work out practical "bugs" and refine design details to increase cost effectiveness and acceptability of this innovative technology for real-world applications. We present results from 14 months of tuning the system design and monitoring energy performance and control system operations. For this southeast-facing office, we found that 1-22\% lighting energy savings, 13-28\% cooling load reductions, and 13-28\% peak cooling load reductions can be achieved by the dynamic system under clear sky and overcast conditions year round, compared to a static, partly closed blind with the same optimized daylighting control system. These energy savings increase if compared to conventional daylighting controls with manually-operated blinds. Monitored data indicated that the control system met design objectives under all weather conditions to within 10\% for at least 90\% of the year. A pilot human factors study indicated that some of our default control settings should be adjusted to increase user satisfaction. With these adjustments, energy savings will decrease. The final prototype design yielded a 10-year simple payback for this site. If mechanical system downsizing opportunities and qualitative improvements to worker{\textquoteright}s comfort are included, this innovative technology could be more cost effective. Marketing information for commercializing this technology is given.

}, author = {Eleanor S. Lee and Dennis L. DiBartolomeo and Edward L. Vine and Stephen E. Selkowitz} } @article {1675, title = {Office Worker Response to an Automated Venetian Blind and Electric Lighting System: A Pilot Study}, journal = {Energy and Buildings}, volume = {28}, year = {1998}, month = {10/1998}, pages = {205-218}, chapter = {205}, abstract = {

A prototype integrated, dynamic building envelope and lighting system designed to optimize daylight admission and solar heat gain rejection on a real-time basis in a commercial office building is evaluated. Office worker response to the system and occupant-based modifications to the control system are investigated to determine if the design and operation of the prototype system can be improved. Key findings from the study are: (1) the prototype integrated envelope and lighting system is ready for field testing, (2) most office workers (N=14) were satisfied with the system, and (3) there were few complaints. Additional studies are needed to explain how illuminance distribution, lighting quality, and room design can affect workplane illuminance preferences.

}, keywords = {behavior, Comfort, commercial buildings, daylighting, envelope}, doi = {10.1016/S0378-7788(98)00023-1}, author = {Edward L. Vine and Eleanor S. Lee and Robert D. Clear and Dennis L. DiBartolomeo and Stephen E. Selkowitz} } @article {12144, title = {Optical Constants of Sputter-Deposited Ti-Ce Oxide and Zr-Ce Oxide Films}, journal = {Applied Optics}, volume = {37}, number = {25}, year = {1998}, month = {09/1998}, pages = {5993-6001}, chapter = {5993}, abstract = {

Films of Ti oxide, Zr oxide, Ce oxide, Ti-Ce oxide, and Zr-Ce oxide were made by means of reactive dc magnetron sputtering in a multitarget arrangement. The films were characterized by x-ray diffraction and electrochemical measurements, both techniques being firmly connected to stoichiometric information. The optical constants n and k were evalued from spectrophotometry and from variable-angle spectroscopic ellipsometry. The two analyses gave consistent results. It was found that n for the mixed-oxide films varied smoothly between the values for the pure oxides, whereas k in the band-gap range showed characteristic differences between Ti-Ce oxide and Zr-Ce oxide. It is speculated that this difference is associated with structural effects.

}, doi = {10.1364/AO.37.005993}, author = {Monica Veszelei and Lisen Kullman and Claes G. Granqvist and Klaus von Rottkay and Michael D. Rubin} } @conference {1932, title = {Tungsten-Vanadium Oxide Sputtered Films for Electrochromic Devices}, booktitle = {Electrochemical Society: Molecular Functions of Electroactive Thin Films}, volume = {98-26}, year = {1998}, month = {11/1998}, address = {Boston, MA}, abstract = {

Mixed vanadium and tungsten oxide films with compositions ranging from 0 to 100\% vanadium (metals basis) were prepared by reactive sputtering from metallic vanadium and tungsten targets in an atmosphere of argon and oxygen. The vanadium content varied smoothly with the fraction of total power applied to the vanadium target. Films containing vanadium were more color neutral than pure tungsten oxide films, tending to gray-brown at high V fraction. The electrochromic switching performance of these films was investigated by in situ monitoring of their visible transmittance during lithium insertion/extraction cycling in a non-aqueous electrolyte (1M LiClO4 in PC). the solar transmittance and reflectance was measured ex-situ. Films with vanadium content greater than about 15\%, exhibited a marked decrease in switching range. The coloration efficiencies followed a similar trend.

}, author = {Thomas J. Richardson and Klaus von Rottkay and Jonathan L. Slack and Franck Michalak and Michael D. Rubin} } @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} } @conference {11778, title = {Effective Medium Approximation of the Optical properties of electrochromic cerium-titanium oxide compounds}, booktitle = {SPIE Proceedings}, volume = {3138}, year = {1997}, month = {07/1997}, pages = {19-Sep}, address = {San Diego, CA}, abstract = {

Cerium titanium oxide samples derived from a solution have been compared against sputtered films over a wide range of different compositions. X-ray diffraction was used to investigate the structural properties of the compound material existing in a two-phase mixture MAO2-MBO2. The optical properties were evaluated over the whole solar spectrum by variable angle spectroscopic ellipsometry combined with spectrophutometry. The spectral complex refractive index was determined for CeO2 and TiO2, as well as for their compounds. To reduce the large number of permutations in composition of multi-component oxides it would be useful to be able to predict the properties of the mixtures from the pure oxide components. Therefore these results were compared to those obtained by effective medium theory utilizing the optical constants of CeO2 and TiO2. In order to investigate the performance as passive counter-electrode in Li+ based electrochromic devices the films were tested by cyclic voltammetry with in-situ transmission control. Chemical composition was measured by Rutherford backscattering spectrometry. Surface morphology was analyzed by atomic force microscopy.

}, keywords = {cerium titanium oxide, effective medium theory, electrochromic, optical constants}, author = {Klaus von Rottkay and Thomas J. Richardson and Michael D. Rubin and Jonathan L. Slack} } @conference {11966, title = {Influence of stoichiometry on the electrochromic cerium-titanium oxide compounds}, booktitle = {11th International Conference of Solid State Ionics}, year = {1997}, month = {11/1997}, address = {Honolulu, Hawaii}, abstract = {

CeO2-TiO2 finds use as passive counter-electrode in electrochromic devices. Thin films were produced by dc-sputtering in a wide range of compositions. Influence of total pressure and oxygen partial pressure on the optical constants of TiO2 was investigated. Slightly substoichiometric TiO2 films exhibit a red-shift of the bandgap. The TiO2 content in the compound essentially determines the degree of cathodical coloring upon Li+ intercalation. However, pure TiO2 films with comparable visible transmittance in the clear state behave differently during electrochemical cycling depending on oxygen stoichiometry. Films that are deposited at higher total pressure are more oxygen rich and require initial formatting until current voltage cycles become stable. CeO2-TiO2 films of intermediate compositions have the relatively highest charge capacity. Comparison with atomic force microscopy indicates a correlation of small grain size with high charge capacity.

}, keywords = {band gap, charge capacity, electrochromic cerium titanium oxide, grain size, optical constants, rms roughness, tio2}, author = {Klaus von Rottkay and Thomas J. Richardson and Michael D. Rubin and Jonathan L. Slack and Lisen Kullman} } @article {1974, title = {Window Optics}, journal = {Solar Energy}, volume = {62}, number = {3}, year = {1997}, pages = {149-161}, abstract = {

Optical and radiative properties of glazing materials are primary inputs for determination of energy performance in buildings. This paper revisits the problem and reformulates the calculations to encompass a variety of solutions to practical problems in window optics. Properties of composite systems such as flexible films applied to rigid glazing and laminated glazing can be predicted from measurements on isolated components in air or other gases. Properties of a series of structures can be generated from those of a base structure. For example, the measured properties of a coated or uncoated substrate can be extended to a range of available substrate thicknesses without the need to measure each thickness. Similarly, a coating type could be transferred by calculation to any other substrate. A simple monolithic model for extrapolating from normal properties to oblique properties is shown to have sufficient accuracy for the purpose of annual energy performance calculations. A process is initiated to develop a reliable method for determination of effective indices suitable for more detailed spectral and directional optical calculations.

}, author = {Michael D. Rubin and Klaus von Rottkay and Rebecca Powles} } @conference {11545, title = {Analysis of Durability in Lithium Nickel Oxide Electrochromic Materials and Devices}, booktitle = {2nd International Meeting on Electrochromism}, year = {1996}, month = {10/1996}, address = {San Diego, CA}, abstract = {

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.

}, author = {Shi-Jie Wen and John B. Kerr and Michael D. Rubin and Jonathan L. Slack and Klaus von Rottkay} } @conference {11793, title = {Electrochromic Lithium Nickel Oxide Thin Film by Pulsed Laser Deposition}, booktitle = {Electrochemical Society Meeting}, volume = {96-24}, year = {1996}, month = {10/1996}, pages = {54-63}, address = {San Antonio, TX}, abstract = {

Thin films of lithium nickel oxide were deposited by pulsed laser deposition (PLD) from targets of pressed LiNiO2 powder with layered structure. The composition, structure and surface air sensitivity of these films were analyzed using a variety of techniques, such as nuclear reaction analysis, Rutherford backscattering spectrometry (RBS), x-ray diffraction, infrared spectroscopy, and atomic force microscopy. Optical properties were measured using a combination of variable angle spectroscopic ellipsometry and spectroradiometry. Crystalline structure, surface morphology and chemical composition of LixNi1-xO thin films depend strongly on deposition oxygen pressure, temperature as well as substrate target distance. The films produced at temperatures lower than 600 {\textdegree}C spontaneously absorb CO2 and H2O at their surface once they are exposed to the air. The films deposited at 600 {\textdegree}C proved to be stable in air over a long period. Even when deposited at room temperature the PLD films are denser and more stable than sputtered films. RBS determined that the best electrochromic films had the stoichiometric composition Li0.5Ni0.5O when deposited at 60 mTorr O2 pressure. Electrochemical tests show that the films exhibit excellent reversibility in the range 1.0 V to 3.4 V versus lithium and long cyclic life stability in a liquid electrolyte half cell. Electrochemical formatting which is used to develop electrochromism in other films and nickel oxide films is not needed for these stoichiometric films. The optical transmission range is almost 70\% at 550 nm for 120 nm thick films.

}, author = {Shi-Jie Wen and Klaus von Rottkay and Michael D. Rubin} } @article {12146, title = {Optical Indices of Electrochromic Tungsten Oxide}, journal = {Thin Solid Films}, volume = {306}, number = {1}, year = {1996}, month = {08/1997}, pages = {10-16}, chapter = {10}, abstract = {

Tungsten trioxide (WO3) is the most widely used material for the active layer of electrochromic devices. Knowledge of the complex refractive index over the range of coloration states is required for device design. Optical constants of WO3 over the whole solar spectrum were determined as a function of injected charge. Films of WO3 were prepared by electron-beam evaporation, then colored in several steps by reduction with lithium (Li) up to 68 mC cm-2 {\textmu}m-1 injected charge. Measurements included variable-angle spectroscopic ellipsometry and spectroscopic transmittance and reflectance at normal incidence. Analysis was complicated by the fact that a transparent-conducting layer of indium tin oxide (ITO) was required to perform lithiation. Optical indices of the glass substrate and ITO transparent conductor were determined separately and then fixed in the model. The indices of WO3 could then be extracted from measurements on the complete structure. A parametric dispersion model corresponding to Gaussian broadening of the oscillators was used to represent the dielectric response of WO3.

}, keywords = {Colored state, Complex refractive index, electrochromic, tungsten oxide}, doi = {10.1016/S0040-6090(97)00254-X}, author = {Klaus von Rottkay and Michael D. Rubin and Shi-Jie Wen} } @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 {12148, title = {Optical Indices of Pyrolitic Tin-Oxide Glass}, booktitle = {Materials Research Society 1996 Spring Meeting}, volume = {426}, year = {1996}, month = {04/1996}, address = {San Francisco, CA}, abstract = {

SnO2:F is a widely used transparent conductor and commercially available in a multilayer structure as Tech glass. Current applications include photovoltaics, electrochromics and displays. Optical design of these and other applications requires knowledge of the optical constants, in some cases, over the whole solar spectrum. Various optical property measurements were performed including variable angle spectroscopic ellipsometry, and spectral transmittance and reflectance measurements. This material is deposited in several steps and has a fairly complex structure. The measured data were fit to models based on this structure to obtain the optical indices. Atomic force microscopy confirmed the optically modeled surface roughness.

}, author = {Klaus von Rottkay and Michael D. Rubin} } @conference {12150, title = {Optical Modeling of a Complete Electrochromic Device}, booktitle = {2nd International Conference on Electrochromics}, year = {1996}, month = {10/1996}, address = {San Diego, CA}, abstract = {

Optical indices have been determined for thin films of all materials needed to model a typical electrochromic device. Two electrochromic materials, tungsten oxide and lithium nickel oxide, are widely used in electrochromic devices. The optical indices of the underlying transparent conductors as well as a polymer electrolyte were also analyzed. The optical data was obtained using a combination of variable-angle spectroscopic ellipsometry and spectroradiometry. The data was then fit to appropriate models of structure and dispersion in order to extract the optical indices of the materials. First, the optical indices of the transparent conductive substrates were obtained and fixed in the model. The best models correspond well to independent physical measurements of film structure, such as atomic-force microscopy and surface profiling. Surface roughness, gradient composition and other types of inhomogeneity are common in both the transparent conductors and electrochromic, resulting in particularly complex models. The polymer has a homogeneous structure, but obtaining optically smooth surfaces was a problem. Complete sets of data were produced over the entire solar spectrum for a range of colored states of the films. Using the data for each layer, a realistic electrochromic device was simulated.

}, author = {Klaus von Rottkay and Michael D. Rubin and John B. Kerr} } @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} } @conference {11610, title = {Characteristics of Laminated Electrochromic Devices Using Polyorganodisulfate Electrodes}, booktitle = {SPIE Proceedings 2017}, year = {1993}, pages = {143}, abstract = {

The use of polyorganodisulfides as optically passive counterelectrodes in a variety of electrochromic devices are discussed. Characteristic data is presented for electrochmmic devices using proton, and lithium coloration ions with polyethylene oxide electrolyte and polydimercaptothiadiazole positive electrodes. Solid state devices consisting of molybdenum doped W03, amorphous polyethylene oxide electrolyte (a-PEO), and a polyorganodisulfide counter-electrode colored rapidly from a pale yellow to a deep blue-green, upon application of 1.2 V d.c. The photopic transmittance changed from 61 to 98, and the solar transmittance from 45 to 5\% during the coloration process. Also, our experiments with polyimidazole are detailed. This family of compounds due to its unique electrical and ion conduction properties allow a single composite ion storage and ion conductor electrode to be made, simplifying the device construction. Devices rnade from this family of compounds color to deep blue-gray upon application of 1.2-1.5 V. Bleaching occurs at -0.4 to -0.5 s. The photopic transmittance changed from 55 to 9\%. and the solar transmittance from 34 to 4\% during coloration. Both coloration and bleaching are quite rapid.

}, author = {Carl M Lampert and Steven J. Visco and Marca M. Doeff and Yan Ping Ma and Yongxiang He and Jean-Christophe Giron} } @techreport {1724, title = {Photoelectric Control of Daylight-Following Lighting Systems}, year = {1989}, month = {02/1989}, abstract = {

The ability of daylight-following lighting systems to provide a minimum specified light level at the task surface is influenced by 1) the control algorithm used, 2) the spatial response of the ceiling-mounted control photosensor and 3) the location of the photosensor relative to task and window. Best performance was obtained with a closed-loop proportional control system controlled by a photosensor, with a large field of view but shielded from direct light from the window. A minimum specified illuminance level could be maintained at specific points on the task surface regardless of daylight condition or room geometry provided that the system gain was properly calibrated to account for the local luminous environment.

Open-loop proportional control also performed adequately but offered less precise control than closed-loop systems due to the necessity of using a photosensor that was not shielded from direct window light. Integral-reset systems that were tested performed poorly, but performance could be improved slightly by completely shielding the photocell from direct window light.

}, author = {Francis M. Rubinstein and Rudolph R. Verderber and Gregory J. Ward} }