Vacuum glazing product named SPACIA^TM, being an unique product with very high levels of thermal insulation properties in a very small thickness, is described in detail. The construction and manufacturing process of SPACIA^TM are reported. Its design, which was originally established by R.E. Collins et al. of the University of Sydney, has been adjusted in order to meet the requirements of the Japanese market and the requirements of mass production process. SPACIA^TM is found to have several unique features including airborne sound insulation as well as thermal insulation. Energy required for air conditioning was simulated for Japanese houses with various glazings, and it was revealed that SPACIA^TM could save the energy efficiently. Finally, hybrid IG unit, where vacuum glazing is incorporated into a conventional IG unit, is proposed for further improvement of thermal insulation.

An innovative Ion-Assisted Filtered Cathodic Arc Deposition (IFCAD) system has been developed for low temperature production of thin-film coatings. The IFCAD system employs electro-magnetic and mechanical filtering techniques to remove unwanted macroparticles and neutral atoms from the plasma stream. Therefore, only ions within a defined energy range arrive at the substrate surface, depositing thin-films with excellent mechanical and optical properties. Ion- Assisted-Deposition is coupled with Filtered Cathodic Arc technology to enhance and modify the arc deposited thin- films. Using an advanced computer controlled plasma beam scanning system, high quality, large area, uniform IFCAD multi-layer film structures are attained. Amorphous Diamond- Like-Carbon films (up to 85% sp3 bonded carbon; and micro- hardness greater than 50 GPa) have been deposited in multi- layer thin-film combinations with other IFCAD source materials (such as: Al₂O₃) for optical and tribological applications. Rutile TiO₂ (refractive index of 2.8 at 500 nm) has been deposited with this technology for advanced optical filter applications. The new IFCAD technology has been included in development programs, such as: plastic and glass lens coatings for optical systems; wear resistant coatings on various metal substrates, ultra smooth, durable, surface hydrophobic coatings for aircraft windows; EUV coatings for space instrumentation; transparent conductive coatings; and UV protective coatings for solar cell concentrator plastic Fresnel lens elements for space power.

The objective of this research program is the development of the technology for the industrial fabrication of large format holographic optical elements (HOEs) with predetermined spectral characteristics and angular selectivity. HOEs of this type are used in a variety of technical applications, such as: holographic concentrators for photo-voltaic energy conversion and solar photo- chemistry or as integrated holographic stacks compromising several holograms operating in different ranges of the solar spectrum for daylighting, glazing and shading in buildings. The latter are required for the effective control of the transmission of solar radiation through the windows or the glass curtain wall envelopes of buildings. The HOEs (reflective or transmissive) are recorded in dichromated gelatin layers deposited on glass or plastic substrates. This material and the corresponding thermochemical development process facilitate the achievement of bandwidths, spectral ranges and angular selectivity that match accurately the design spectral and geometrical properties of a particular application.

A photonic band gap structure is periodic lattice of high and low refractive index materials that form pass bands and stop bands (band gaps) in analogy with electronic band gaps. Since metals are highly reflective, it was thought that a photonic band gap crystal containing alternating layers of metal and dielectric would not exhibit a photonic band structure. It was expected that all electromagnetic radiation would be reflected or absorbed and none would be transmitted. However, resonant tunneling through multiple metal films can enhance the transmission by several orders of magnitude. The periodic nature of the metal/dielectric lattice causes the light to propagate through the metal layers with extremely low loss. Perhaps the most unique feature of the metallic optical filter is the ability to have a single pass band and block all other radiation from static fields to soft X-rays. This remarkable property is a result of the highly dispersive nature of metals.

Antireflection (AR) coatings can be incorporated into highly transmitting glazings that, depending upon their cost, performance, and durability of optical properties, can be economically viable in solar collectors, agricultural greenhouses, and PV systems. A number of AR-coated glazings have been prepared under the auspices of the International Energy Agency Working Group on Durability of Materials for Solar Thermal Collectors. The AR coatings are of two types, including (1) various sol-gels applied to glass and (2) an embossed treatment of sheet acrylic. Typically, for unweathered glazings, a 4 - 5% increase in solar-weighted transmittance has been achieved. For AR-coated glass, reflectance values as low as 0.5% - 0.7% at selected wavelengths (680 - 720 nm) were obtained. To determine the durability of the hemispherical transmittance, several collaborating countries are testing these materials both outdoors and in accelerated weathering chambers. All materials exposed outdoors are affixed to mini-collector boxes to simulate flat-plate collector conditions. Results for candidate AR coatings weathered at geographically disperse outdoor test sites exhibit changes in spectral transmittance primarily in the high visible range (600 - 700 nm). Accelerated testing at measured levels of simulated solar irradiance, and at different constant levels of temperature and relative humidity have been performed in different countries. Parallel testing with different levels of laboratory-controlled relevant stress factors permits the time-dependent performance of these materials to be compared with measured results from in-service outdoor exposure conditions. Coating adhesion and performance loss resulting from dirt and dust retention are also discussed.

Alumina, Al₂O₃, films were prepared by the sol-gel process and deposited by spin coating technique. The coating solutions were synthesized by using aluminum-sec butoxide, Al(O^SBu)₃, as a precursor, isopropanol as a solvent, acetylacetone, AcAcH, as a chelating agent and nitric acid, HNO₃ as catalyzer. Highly transparent alumina coatings with thickness in the range of 100 - 700 nm were prepared at different spinning rates and heat treated at 400 degree(s)C. The morphology, microstructure, transmittance characteristics of the films were investigated. The investigations were performed by optical and Fourier infrared spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM examinations and spectrophotometric measurements show that the films were homogeneous and uniform with a visible light transmittance higher than 90%. XRD of the alumina films heat treated at the temperatures below 500 degree(s)C showed that they had an amorphous structure. XPS examination showed that amorphous films were stoichiometric Al₂O₃.

In regards to fenestration (window) systems, calorimetry is defined as the solar radiation incident upon a glazing aperture to a well insulated testing chamber and the transfer of energy through this aperture. Solar calorimetric instrumentation has traditionally involved the measurement of heat exchange using water driven collectors. Standards have yet to be set for the exact apparatus and procedure on solar calorimetry for glazing systems. The accepted procedure for external testing is to expose the calorimeter to clear external conditions and constant solar position via solar tracking.

This paper discusses the critical strategic research and development issues in the development of next-generation photovoltaic technologies, emphasizing thin-film technologies that are believed to ultimately lead to lower production costs. The critical research and development issues for each technology are identified. An attempt is made to identify the strengths and weaknesses of the different technologies, and to identify opportunities for fundamental research activities suited to advance the introduction of improved photovoltaic modules.

Structural, optical and electrical characterization has been conducted on CuInS₂ (CIS) thin film fabricated via spray CVD technique. Both RBS and Raman scattering analyses suggest that the film is slightly Cu rich by approximately 2%. XRD measurement indicates the film is polycrystalline CuInS₂ with [220] orientation on a quartz substrate with a possible Cu_1.7In_0.05S secondary phase (< 3%) co-existing with CIS. The measured optical band gap of the film is about 1.44 eV. Hall effect measurements suggest that the film is p-type. Both measured mobility and resistivity are consistent with those of the bulk. The combination of AFM, STM and electrical measurements indicate that grain boundaries may be the charge carrier transport limiting factors. However, the presence of a secondary non- chalcopyrite phase is complicated the current study. It is still not clear the nature of the hole transport is due to so called `intrinsic doping' and `native defects' in the micron sized CIS crystals, or to the presence of a secondary phase or to the grain boundaries. It is shown that Raman and IR spectroscopy can be powerful tools to study the film stoichiometry, structural composition and molecular species present in the film.

Molybdenum dichalcogenides are semiconductors, which can act as efficient electrode in the realization of photoelectrochemical solar cells. Layered semiconductors may also be of considerable interest for other than photovoltaic applications like high temperature, high vacuum lubricants, substrates for Langmuir-Blodgett films or large molecules (DNA, RNA etc.,) as a suitable for glass or graphite. Among molybdenum dichalcogenides (S₂, Se₂ and Te₂), MoSe₂ has led to the best solid state cells with efficiencies exceeding 6%. The main advantage of these MoSe₂ semiconductor is the prevention of electrolyte corrosion, because of the phototransitions involve non- bonding d-d orbital of the Mo atoms.

Photothermal deflection spectroscopy is used to investigate the optical properties of CuInSe₂ thin film semiconductors, which are different in composition and technical preparation conditions. It is found in the experiment that absorption coefficient and direct band gap of the samples can be changed under the control of substrate temperature and proportion of [Cu]/[In], which agrees with the reported results by other methods.

The importance of renewable energy sources is currently attracting widespread attention due to the limited availability of fuels and major environmental impacts. A great deal of effort is put our days on the development of new efficient solar energy collectors either by quantum or thermal conversion. On this communication we will refers just to thermal converters focusing on the roughness and microtopographic inspection of surface thin films and spectrally selective coatings. Physically Vapor Deposited coatings like sputter deposited metal oxide and nitride thin multilayered and graded ones can be used in spectrally selective surfaces for thermal collectors and energy- efficient windows.

Luminescent Solar Concentrators (LSC's) were thoroughly explored over a decade ago for use with photovoltaic cells. However LSC's as a source for lighting have received less attention than is deserved. To evaluate the lumens supplied by a LSC lighting source over the course of a year and in a fixed orientation it is necessary to know the light-to-light conversion efficiency. We present a model for this and examine its sensitivity to the geometry of the LSC and light transport losses for light guided within the LSC. The latter depends on dye concentration due to spectral overlaps of the absorption and emission bands and to bulk and surface losses due to defects. As a result of these effects the spectral distribution of the emitted light, and hence the color rendering properties, depend on the size of the LSC. Calculated spectra are compared with those measured in the laboratory for full scale LSC's. Results for calculated efficiency as a function of length and dye concentration are given. It is found that properly orientated compact LSC's can provide enough lumens under moderate external illuminance to illuminate a typical room in a house.

Aluminum is a good candidate for both solar and visible angular selectivity if used in metal/high refractive index insulator combinations, but angular selectivity was not observed in Al/TiO₂ films prepared in traditional co- deposition techniques. A new approach, deposition of a thin oblique Al layer, then oblique TiO₂, and later annealing in vacuum, was attempted and good angular selectivity observed in this material combination. In contrast to other angular selective films, these films showed angular selectivity in s-polarized light for the plane of incidence parallel to the TiO₂ columns. Spectral transmittance plots show the effects of Al content and annealing temperature of angular selectivity. SEM micrographs confirm the oblique columnar structure of the annealed complex, and inter-diffusion of Al through the TiO₂ columns.

Titanium dioxide (TiO₂) films have been deposited on SnO₂ coated glass substrates by screen-printing. Film morphology and structure have been characterized by scanning electron microscopy, x-ray diffraction and BET analysis. Dye-sensitized TiO₂ photoelectrochemical cells have been assembled and characterized. Cells sensitized with anthocyanin and a ruthenium complex have been investigated. A 0.77 cm² ruthenium dye sensitized cell with 6.1% power conversion efficiency under Air Mass (AM1.5) conditions was obtained. Results obtained with a pure anthocyanin dye and dye extracted from blackberries were compared. Finally, a natural gel was found to improve the stability of anthocyanin sensitized cells.

Silver-dielectric composite films were produced by a biomimetic technique, using the bacterial strain Pseudomonas stutzeri AG259 as a precursor for sol-gel-type deposition. Heat treated films backed by a metal displayed pronounced spectral selectivity of a kind that makes them interesting for photothermal conversion of solar energy. The optical properties could be reconciled with the Bruggeman effective medium theory.

The electrochromic (EC) property, reversible coloration of certain materials under double injection of ions and electrons, of transition metal oxides (TMO) such as tungsten trioxide is known to depend strongly on the nature and structure of these materials. Possibility exists to tailor the EC behavior of the different TMOs as per the optical modulation needed. In this work the electrochromic performance of three types of tungsten trioxide films deposited under different conditions leading to nanocrystalline, polycrystalline and amorphous films has been studied by dry lithiation method. A comparative study of the EC coloration of these three types of films has been carried out, with a special emphasis on the nanocrystalline films. The techniques of spectrophotometry and atomic force microscopy have been employed for this study. Each type of tungsten trioxide (WO₃) film exhibits a special nature of coloration indicating the potential for its specific application. The nanocrystalline films seem to exhibit a higher overall coloration efficiency and a selective optical modulation compared to the polycrystalline or amorphous films. These films exhibit a very high degree of transmission in the clear state and a high degree of optical modulation concentrated in the infrared region. Hence, the NC films may be of more interest for smart windows from the point of view of energy efficiency. The amorphous films, and even the polycrystalline films under high degree of lithiation, may be more suited for large area display device application due to their efficiency coloration in the visible region of the spectra.

The problem of scaling the impinging solar radiation spectrum, to the excitance of blackbodies on earth at moderate temperatures is discussed. Typically diagrams with these two kinds of spectra are used to demonstrate wavelength separation as the background for solar, optical selectivity. All spectra can satisfactorily be approximated with Planck curves, but the solar spectrum must be reduced in intensity because of the long distance Earth - Sun. Some difficulties with using astronomical data for this scaling are noted. As an alternative, the T⁵-dependence of the Planck curve maxima, when drawn on a wavelength axis, is used to demonstrate that the curves can be scaled based on their total energy and solar absorber stagnation. The ratios of the peaks of the impinging solar radiation to the excitance spectra for black surfaces on earth at various ordinary temperatures are reported. It is pointed out that the choice of independent variable effects the positions of the Planck function peaks, as well the shape of the spectra. The peak values increase proportionally to T³ when frequency is used instead of wavelength and the width of the curves grows linearily with temperature. Effects of using a logarithmic wavelength scale are also noted.