Fundamental properties of the transmissive electrochromic device are described. The device comprises of a semi-solid electrolyte and a WO3 film sandwiched by a pair of transparent electroconductive sheet glasses. The transmittance of the device can be arbitrarily controlled within the range from 80% to 10%. The response time was found to be greatly depended on the size. The life time for the repetitive operations is more than 105 cycles. Fairly good durability against the outdoor conditions has been clarified. This device is capable of controlling reflectance of mirror when a reflective layer is coated on the either surface of outer glass. Outline of this reflective device is also described. The reflectance of the mirror of the size of 25cm x 6.5cm can be changed from 72% to 20% within 4sec at 1.5VDC. This device is suitable for anti-dazzling mirror of motor cars.

Electrochromic hydrated nickel oxide films were produced by reactive rf-magnetron sputtering followed by electrochemical treatment in KOH. Spectrophotometry was used to study the modulation of luminous and solar transmittance and to assess the durability. 15N nuclear reaction analysis showed that coloration occurred upon hydrogen extraction. The investigated coatings appear to have very good properties for smart window applications.

The electrochrcrnic properties of hydrated nickel oxide thin films electrochemically deposited by anodization onto doped tin oxide-coated glass have been studied by transmittance measurements, cyclic voltammetry, Fourier-transform infrared spectroscopy, and ion-backscattering spectrometry. The spectral transmittance is reported for films switched in both the bleached and colored states. The photopic transmittance (Tp) can be switched from T (bleached) = 0.77 to T (colored) = 0.21, and the solar transmittance (Ts) can be switched from Ts(bleached) = 0.73 to TS (colored) = 0.35. Also reported is the near-infrared transmittance (TNIR)which was found to switch fran T N,IR (bleached) = 0.72 to TNIR (colored) = 0.55. The bleached condition is noted to have very low solar absorption in both the visible and solar regions. Ion-backscattering spectrometry was performed on the hydrated nickel oxide film, yielding a camposition of Ni01.0 (dehydrated) and a film thickness of 125 A. Cyclic voltammetry showed that, for films in the bleached or colored state, the reversible reaction is Ni(0H), = NiOOH + H+ + e . Voltammnetry also showed that the switching of the film is controlled by the diffusion or protons, where OH plays a role in the reaction mechanism. Analysis of the hydrated nickel-oxide thin films by Fourier-transform infrared spectroscopy revealed that both the bleached and colored states contain lattice water and hydroxyl groups. The surface hydroxyl groups play an important role in the coloration and bleaching of the anodically deposited nickel oxide thin films.

Any system for the utilisation of solar energy requires to be of large area because of the low energy density of the radiation. It also requires to be highly thermally insulating to prevent the loss of low temperature heat that is gained. To be cost-effective in any application requires that a coating made to improve a system has to be made in large areas at low cost. In a vacuum system of high capital cost this means that a high speed process is required. The process of reactive planar magnetron sputtering is considered in terms of these criteria with examples given of the preparation of oxide-metal-oxide and conducting oxide filters as low emissivity transparent surfaces. Recent advances in the preparation of such filters are described, These include the use of anti-reflecting layers on conducting oxides and more precise deposition techniques for the preparation of the oxide in a thin metal-containing structure. The preparation and properties of tungsten oxide are described with the view of more advanced developments including the use of the electro chromic effect as well as a new material for a heat reflecting filter.

The electrochromic response time and the chemical and electrochemical stability of amorphous tungsten oxide layers have been found to be adversely affected by the degree of porosity and hydration of the oxide layers 1,2, thus complicating the preparation of stable high speed electrochromic films. Based on our investigations of the microstructure of thermally evaporated tungsten oxide we could overcome this problem by preparing high density (P = 6.4 g cm-3) tungsten oxide layers by flash evaporation or by reactive dc sputtering. In spite of the higher packing density (reduced free volume) which increased the electro-chemical stability remarkably, the electrochromic response time of thin layers could be re-duced to 50 ms to reach a contrast ratio of 1 : 2 at 633 nm, which is comparable to that of sputtered iridium oxide films. Even with 1.6 4m thick dc sputtered tungsten oxide layers a response time of 400 ms for a contrast ratio of 1 : 2 and a response time of 5 s for a contrast ratio of 1 : 1000 could be achieved.

Polycrystalline tungsten oxide W03 thin films were prepared by oxidation at high tempera-ture of tungsten compound layers deposited by chemical vapor deposition of W(CO)6. Structure, optical characteristics (n and k) and density of the films were determined. Transparent electrochromic configurations were prepared by deposition of a thin film of this oxide on a Sn02 coated glass.

Electrochromic tungsten trioxide films have been prepared by d.c. reactive sputtering of metallic tungsten target in Ar-02 mixture. The structural and the optical properties of tungsten trioxide films have been investigated for the different sputtering conditions. The operating electrochromic characteristics as the current density and the transmission versus switching voltage have been presented. The dynamical properties of EC system have been measured and calculated from diffusion model. The diffusion coefficient of hydrogen atoms into the W03 were found to depend on sputtering conditions.

Unstructured electrochromic mirrors with variable reflectance have been developed on the basis of hydrogen tungsten bronzes. The characteristic compounds of these devices are (1) solid ion-conducting layers ("electrolytes") resulting in only few micrometer thick all-solid-state systems, which can be enclosed between the substrate and a second glass plate and are thus protected from the environment, (2) integrated reflecting metal layers, and (3) hydrogen-storing electrochromic layers. Two basically different constructions are feasible. In "diffusion-driven" devices the bronze is formed (decomposed) by the chemical reaction x/2 H2+ W03⇔HxW03, in "field-driven" systems an electrochemical bronze formation (decomposition), x H + W03+ x e HxW03, takes place. The modes of construction are presented and compared, the electrochemistry of the thin layer cells involved is discussed, the prop-erties of devices according to the state of development are reported, and possible applications, e.g. as glare-free, inside and outside, automotive rear view mirrors with adjustable reflectance, are briefly described.

Different kinds of transparent insulation materials were investigated. The thermal conductivity was found to depend mainly on thermal radiation. For this reason it was found to be generally sufficient to classify the materials by only one radiative property. The improvement of thermal insulation by application of a selective absorber was investigated by measurements and calculations. A new configuration to combine a selective absorber with a transparent insulation is proposed. Some spectral measurements were done and compared with calculations. Radiative grey characterization was compared with spectral characterization.

At ambient temperatures, transparent silica aerogels as well as translucent granular fillings are excellent superinsulating spacers if evacuated. Thus their use in windows and covers for passive solar systems is extremely promising. Thermal loss coefficients under variation of radiative temperature, sample density, boundary emissivity and internal gas pressure are presented. Furthermore, the scaling of the solid conductivity with density is discussed.

We investigate the radiative heat transfer between blackbody-like surfaces confining an infrared-absorbing gas layer. Spectrophotometric measurements on selected gases lead us to optimized compositions with sulfur hexafluoride, propyne, and different freons. Theoretically, the gas is able to diminish the radiative heat flux across a 1 cm thick slab by a factor - 0.7 in comparison with the case of a non-absorbing medium. Infrared-absorbing gases seem to offer interesting possibilities for improved transparent thermal insulation of windows.

Transparent insulation materials for solar energy applications are classified and described in this paper. An experimental set-up with an integrating sphere for the whole global spectrum range having a large entrance port is capable of measuring angle-dependent directional-hemispherical transmittances for planar samples and non-planar structures with acceptable accuracy up to about 70 degrees. The theoretical description of such structures allows to calculate directional transmittances even for combinations of different kinds of layers, for instance to determine seasonal variations of monthly-averaged transmittances for the whole cover system.

Two glass types for luminescent solar concentrators are presented: Type 1 is a silicate glass activated with Yb203, Nd203 and Cr20. This type shows luminescence in the region 970-1080 nm. It is possible to use it in combination with a silicon detector. The glass type 2 is a borosilicate glass activated with UO2. Its wavelength region of luminescence is 510-560 nm. It can be used in combination with a CdS/Cu2S or GaAs photo detector respectively.

The interest in efficient daylighting systems has grown recently, due to their potential for saving a considerable amount of electrical energy used for lighting purposes. In this paper we discuss the properties of daylighting systems based on either fluorescent planar concentrators and transparent light guiding plates or light pipes coated with highly reflective silver coated plastic films. Finally we give first results from a demonstration project, daylighting systems in the students' living quarters in Stuttgart-Hohenheim, which is supported by the Commission of the European Communities.

Energy transfer between fluorescent dye molecules and small silver particles can improve the apparent fluorescence quantum yield for the dye, provided that the silver particles are of a suitable size and form to amplify the total absorption and fluorescence. This mechanism provides a possibility for extending the range of dyes which could be used in fluorescent collectors to longer wavelengths, by increasing the quantum yield and long-term stability of dyes absorbing in the NIR. Composite material models of the optical characteristics and measurements of the absorption, fluorescence and fluorescence lifetime are used to investigate this effect.

A mathematical model was developed for a transparent planar light concentrator based on diffuse scattering of light. The model may be used in predicting the short-circuit current from different modifications of the collector in connection with solar cells.

A modification of a luminescent solar concentrator was studied. The upper side edges of a luminescent plate were rounded and the solar cells were attached onto the lower side of the rounded edges, so that both the luminescent radiation and the transmitted light could be collected. The optimum shape of the rounded edge was mathematically derived.

The relaxation of a few typical orange and red absorbing dyes in PMMA ( polymethylmetacrylate ) is studied by compensation photocalorimetry and picosecond fluorescence spectroscopy. At ambient temperature the orange dyes have a fluorescence quantum efficiency of close to unity and they decay monoexponentially. The red dyes have lower efficiencies and their decay can be described by two exponentials. This decay kinetic is not in agreement with the model of dipol-dipol mediated intramolecular fluorescence quenching.

Transparent conducting zinc oxide films have been prepared by reactive sputtering in an Ar/H2 mixture. The optical and electrical properties of the films are presented and discussed. The effects of some post-deposition thermal treatment have been also investigated. ZnO/CdTe heterojunctions have .been prepared by sputtering ZnO films on CdTe single crystals. The photovoltaic conversion efficiencies of the obtained solar cells was 6.8%.

Cadmium-tin oxide (CTO) films have been prepared by d.c. reactive sputtering of Cd-Sn alloy targets in Ar-02 gas mixture. The electrical, optical and structural properties as well as the chemical composition of transparent conducting CTO films were found to depend on sputtering conditions. The value of optical band gap, optical constants, effective mass and relaxation time of electrons have been determined.

Fluorine-doped tin dioxide layers have been producted by spraying an organic tin solution on a hot substrate. The substrates were common window glass, pyrex and black enamelled steel. Best results are obtained with black enamelled steel. Typical values of the spectral selective layer are in that case: a solar absorptance of 0.92 and a thermal emittance of 0.15. Aging tests have been carried out in air and in vacuum. In vacuum above about 250° C aging effects occur, which are related to a decrease of the-Sn0-fraction of the layer. The effect of sodium, which can diffuse from the glass substrate into the layer, is also investigated. Experiments show that only unrealistic high concentrations of sodium give significant changes of the properties of the layer.

The influence of the deposition parameters on the electrical and optical properties of very thin silver films prepared by magnetron sputtering was studied. To evaluate the film properties a method was used, which is based on simple optical transmission measurements, and was proposed recently by one of the authors /1/. The results show that the specific resistivity, the plasma energy and the optical resistivity of films below 30 nm thickness are very sensitive to deposition parameters as cathode power density. It is concluded that the obtained variations in the optical and electrical properties are related to the density of the sputtered films.

The combination of visible transmittance and IR-reflectance of a heat-mirror is essentially a property of a Drude-type material. The difference between the heat-mirror materials is that the desired transmittance occurs in different spectral regions of the Dnxie model and accordingly is subjected to different optical limitations. Based on these observations the existing transparent heat-mirrors are optically classified and new materials like TiN, ZrN, HfN LaB6, GdSe, Ir02, Ru02' Re03 and NaxWO3 are suggested.

Transparent metallic conductors are being increasingly utilized in solar cells, display systems and a wide range of opto-electronic devices. Indium-Tin-Oxide (I.T.O.) has been widely employed in this role. Recently, cadmium stannate has also been utilized as an optically transmissive cathode contact in prototype electroluminescent displays (Kirton et. al.). In many instances, the conversion properties of an opto-electronic device are limited by the optical transmission and reflection properties of the interfaces formed between the transparent conductor and other semiconducting materials. These may in turn be controlled by chemical and/or metallurgical reactions occurring at an interface.

The efficiencies for total solar cogeneration (TSC) can be optimized by tailoring the transparent heat-mirror (HM) beam splitter spectral profile shape. The entire output is cogenerated by photovoltaic/photothermal conversions into three energy forms: electricity (PV) 18V d.c./module, high-temperature heat (HT) 400°C, and low-temperature heat (LT) 70°C. The emphasis is to maximize the high-quality energy sum PV + HT, while maintaining PV at a high level. A generalized 5-parameter double Fermi model for the HM spectral profile is investigated allowing for a wide parametric range and profile asymmetry. The projected optimized TSC conversion efficiencies are: PV = 14.3%, HT = 43.5%, and LT = 42.2% with a high-quality energy sum of PV + HT = 57.8%. The approach to this optimum HM spectral profile by experimental HM films such as ITO are discussed.

During the past several years, a high level of activity has been directed toward developing more efficient lighting products to meet consumer demand in the face of energy scarcity and its high cost. Without major redesign of lamps, manufacturers have been able to achieve modest gains of 5 to 10 percent in incandescent lamp efficacy by optimizing standard features such as filament design, gas fill, etc. What was desired for incandescent lamps was a major jump in efficacy of 30% or more. Much encouraging work, notably by Philips in the Netherlands, has already been accomplished in the laboratory using thin film reflectors to recycle the wasted infrared radiation from incandescent lamps. Indium tin oxide (ITO) films, which are transparent in the visible and reflect well at wavelengths greater than 2 micrometers, is a most attractive material for its simplicity and apparent high performance. It °has a serious drawback, however, in its inability to reflect adequately when its temperature exceeds 800 C. A separate outer jacket surrounding the lamp itself is required in order to keep the ITO coating cool and thereby take advantage of its properties. The use of this extra component makes this solution to the energy problem more expensive and complex. In the United States, the Duratest Corporation has developed a sophisticated silver coating which is deposited inside domestic type A-line lamps. About six years ago, the General Electric Co., a major U.S. lamp manufacturer, approached 0.C.L.I. and requested assistance in improving the quartz-halogen lamp. The G.E.-0.C.L.I. method that was developed for improving the efficacy of an incandescent lamp product consists of coating quartz-halogen lamps with infrared reflectors. These reflectors are interference reflector stacks made of refractory metal oxides using conventional thermal evaporation technology. These products have been available commercially for about three years.

Different forms of spectrally selective black cobalt solar absorber surfaces have been prepared using direct electrodeposition and electrodeposition followed by chemical oxidation or thermal oxidation. The dependence of surface optical properties on the deposition process conditions has been studied. Compositional and microstructural properties have been examined using a range of surface analytical techniques. The effects of exposure of black cobalt surfaces in air at temperatures up to 500°C have been examined. Favourable conclusions are drawn for the performance of a CoO(OH) surface formed by chemical oxidation and for a fully oxidised cobalt metal film formed by thermal oxidation in air. In the latter case film thickness and surface microstructure are shown to have pronounced effects on the surface optical properties.

The solar selective properties of fluorine doped tin oxide on anodized aluminium have been investigated. The tin oxide was pyrolytically sprayed on black nickel pigmented anodized aluminium, heated to about 450°C. The results show that the total solar absorption of this tandem exceeds 0.9 with a thermal emittance of around 0.2. Owing to the exceptional chemical, thermal and mechanical stability of the tin oxide coating this selective surface turns out to be remarkably resistant to accelerated ageing.

The temperature stability of solar selective absorbing Cr-SiO-cermets on Cu and Cr/Cu-subsotrates was tested. The cermets were prepared by rf sputtering. Thermal annealing up to 900C was done in air, Ar and vacuum for periods up to 28 days. Some crystal growth and stable optical properties were observed.

The absorber-reflector tandem configuration is used for the realization of a selective absorbing surface for the photothermal conversion of solar energy. The infrared reflector consists of a stainless steel substrate, covered or not with a W or Mo thick film. The visible absorbing function is realized by a thin, low cost, Fe-A1,0, cermet film. The cermet films are prepared by R.F. co-sputtering onto a rotating stainless steel substr'te. The target consists of a circular Al203 plate covered with small discs, the concentration varying with the Fe disc number. The optical properties of the thin Fe-Al203 are studied as a function of the Fe volume fraction from 0.2 to 0.9. The dielectric function is calculated from the reflectivity and transmittivity measurements in the 300-50.000 nm spectral range. The films exhibiting the required selective properties : high absorptivity in the visible, high transparency in the infrared, are selected. A sandwich, composed of a thin Al203 antireflecting film, the cermet film (with adequate thickness and composition) and the reflecting substrate, exhibits a good selectivity for the photothermal conversion at low and middle temperatures.

The reflectivity spectra of sputtered zirconium and titanium nitride, carbide and carbonitride thin films have been studied. The data are interpreted by means of their electronic structure in a Drude-Lorentz model. The influence of the nature of the metal and of the non metals is qualitatively understood. Although no good solar absorber is reported here, this study shows that the optical profile of the ternary compounds can be tailored in a wide range between those of the binary compounds.

Preliminary results of the spectral selective characteristics of a cermet composed of a semiconducting cuprous oxide Cu20, in the matrix of a dielectric film of aluminium oxide, Al203, is presented for the first time. The composite film is charcterised by a hemispherical absorptance,∝, of 0.83, and thermal emittance at 100°C, eT of 0.29. These properties are observed to be little affected by a prolonged heating of the film in atmospheric air at 200°C for many hours.

The creation of a rough surface state allows a modification of optical properties. Deposits of electroless layers of Ni-P have been realized on metallic (steel, aluminium), plastic and glass substrates. The layers are obtained by electroless process using the reduction of nickel ions by the hypophosphite ions. The non metallic surfaces must undergo pretraitment by chemical activation before plating. The layers have a rough surface state formed by juxtaposed nodules. When dipped in a nitric acid solution, the surface presents a blackening resulting from hole formation visible first on the boundaries between the nodules and then, on the whole deposit surface. During etching, absorptance as increases with etching time, and reaches values higher than 95%. Emittance ε remains weak and near 20%. We follow the evolution of optical, thermal, physical and chemical properties after aging. Several analytical methods have been employed like XPS, Auger spectroscopy, electron microprobe, EDAX, electron microscopies, etc. We show that the selectivity results from the creation of a rough surface state and that the effect of the acid etching on the optical properties is bound to the initial structure of the alloy. The optical properties are simulated by the utilization of a statistical model of roughness. An interpretation of the attack phenomenon is given that takes into account kinetics with two reaction rates depending on the microstructure of the as-prepared material.

Selective optical properties can be achieved by a suitable surface roughness. Characteristic parameters describing the roughness of the surface profile are the rms-roughness, the rms-slope, and the autocorrelation length. The relation between these parameters and the spectral reflectance of the considered surface is known approximately from the scalar scattering theory. Due to the dimensions of the investigated surface profiles the roughness measurements require scanning electron microscopy for surface imaging. For the statistical evaluation the image data are processed in a computer system, which performs the Fourier-transformation of the whole image. The square of the Fourier transform yields the spectrum of the spatial frequencies from which the autocorrelation function and the correlation length can be derived by inverse Fourier-transformation. The scanning electron microscope causes a systematic imaging error, which can be corrected by approximating the image signal as a superposition of the surface height and its slope. The results are compared with the results of spectral measurements of the specular as well as the hemispherical reflection in the IR-rage applying the scalar theory mentioned above for copper-oxide and chromium absorber coatings.

Good durability of solar absorber coatings is one of the most important preconditions for their application. Since the lifetime of an absorber should be at least ten years, a prediction of the ageing behaviour by accelerated ageing tests is very desirable. In general the ageing due to temperature loads of the coatings is caused by chemical or diffusion processes. The temperature dependence of the chemical reaction velocities as well as of the diffusion constants is described by Arrhenius'law. Therefore an increase of the test temperature leads to an accelerated ageing. The degradation of the optical properties of the layer (e. g. solar absorptance and thermal emittance) at high temperatures as a function of time, caused by the enhanced temperatures, can be transformed to lower temperatures using Arrhenius'law. Thus an estimation of the ageing behaviour and the lifetime at operating temperatures is possible. This method is applied to copper-oxide coatings and to Ni-MgF2 cermets. The specific ageing processes have been investigated by Auger-electron-spectroscopy combined with energy-dispersive x-ray analysis, which has shown, that the degradation of the copper-oxide layers is caused by chemical processes while the ageing processes in Ni-MgF2 coatings are dominated by diffusion processes.

Aging (under heating in air at 100°C ) of Cu and Cu - Cr coatings on glass substrates has been studied by measuring the spectral transmittance and reflectance in the wavelength range 0,4 - 25pm. The results show a fast oxidation of copper films. In the case of Cu-Cr double layer system an initial increase of the IR reflectance has been observed. After this stage the system shows a selectivity similar to that of a single as-received Cu films and very good stability to the oxidation. The prolonged heating (up to 600 h) in air at 100°C does not essentially change the IR reflectance of the Cu - Cr system. The increase of the IR reflectance of Cu - Cr coatings in the initial stage of heating and their further stability has been explained, supposing an oxidation of the Cr layer.

Five composite materials of Al-N have been prepared by dc magnetron reactive sputtering techniques. Good agreement is obtained between computed and experimentily measured reflec-tances and absorptances for Al-N/Al(AD). Solar absorptance of Al-N/A1 selective surface(HT) is - 0.92 and emittance - 0.04 at room temperature. Gas evolution from sputtered Al-N/Al has been studied using thermomanometry and mass spectrometry. The total outgassing from the surface is considerably low.

The effect of high solar flux on the catalytic methapation reaction has been investigated. Irradiation of the nickel catalyst at a flux of 1.4 MW/m2 resulted in a 100% increase in methane yield for the reaction. This high flux photo-enhancement is believed to be due to photo-enhanced dissociation of the CO molecule on the nickel catalyst surface.

Measurements of the near-normal/hemispherical reflectance in the infrared spectral range can be taken by using integrating spheres as photometric integrators. In the infrared region, where the reflectance of the sphere coating significantly differs from one, the specular component of the reflected flux causes problems due to the different weighting of the specularly and diffusely reflected part by the sphere wall. An evaluation method for circumventing these difficulties is presented. It is shown that the influence of the sample indicatrix can be eliminated with a good accurracy if the specular reflectance factor is known. The considerations are based on investigations in the spectral range from 1 μm to 15 μm performed with a Fourierspectrometer and a gold coated integrating sphere. Examples demonstrate the application of this method for the investigation of samples whose specular reflectance factors change with wavelength. That especially occurs if the selective properties of solar absorber coatings is caused by surface roughness. The described method can be applied to estimate the surface roughness parameters and to characterize the optical properties of selective solar absorber layers.

Opitical fibers with not uniform terminations to be used for a better collection and trasmission of light have been carefully analyzed. The coupling efficiency of a plane wave with a linearly tapered fiber has been calculated in different geometrical conditions. Developments and some interesting applications are discussed.

The saddle field source has for many years played a unique role in the preparation of specimens for electron microscopy and in mass spectrometry analysis. It is the purpose of this work to show where the advantages of this unique source are now being successfully exploited in the field of thin film deposition.

The single-layer coatings on the base of strongly alloy semiconductors, meeting such demands as high reflective capacity in near infrared area of spectrum, are considered. The calculations and estimation of the reflective capacity of the model semiconductors are given. The results of investigation on optimization of the parameters of strongly alloy semiconductors are also given.

The aim of this work is to analyze the behaviour of a thin layer of semiconducting CdS, used as photosensible anode in a photoelectrolyitical cell, when the same electrode is covered by a thin layer of a non-conducting polymer. Such a structure should permit a protection against the photocorrosion effects, that, as well known, are considerable for the Cadmium Sulfide and, generally, for all the semiconductors with a small value of the interband gap. This procedure ought to allow a long term stability of the electrodes. With this purpouse it has been measured the rate at which the photocurrent, exhibited by the dispositives, decreases in time as a function of the polymer thickness. The choose of the Formvar (polyvinylformale) as the polymer, was suggested by the large use made, in former times, by the same authors, of this material in junction devices, where the electric charge conduction was by tunnel effect.

It is shown that thick transmission phase holograms can either be chromatically selective or non-selective depending on the design of geometrical conditions of recording and processing of holograms. Theoretically plotted curves show that by appropriate selection of recording parametes and geometry, holographic optics can be fabricated to use almost entire useful spectrum of the sun with a reasonably good efficiency.

Amorphous solar cells are becoming important in energy-related fields all over the world. Indeed in Japan, amorphous solar cell R & D, which was begun as a national project in 1980, has now made the leap from basic research to partial applications research. The level of amorphous solar cell R & D in Japan is now the highest in the world, and one might say that we have become the Mecca of this field of research, matched avidly by all other countries. Being presented is the outline of amorphous solar cell R & D as a national project in Japan, "Sun-Shine Project."

A preliminary report of some optical and electron spin resonance (ESR) properties of hydrogenated amorphous silicon (aSi:H) films prepared by rf sputtering in 10 mtorr He, 0.5 mtorr H2, and varying rf power is presented. As the rf power is decreased from 3.3 to 0.27 W/cm2, the deposition rate also decreases but the concentration of Si-H and Si-H2 bonds, the optical energy gap Eq, and the dangling bond spin density all increase. In particular, the optical gap of the He/H2 sputtered films increases from 1.65 to 2.09 eV and is considerably higher than for films sputtered by Ar/H2 under similar conditions. The gap is, however, only slightly higher than that of Ar/H2 sputtered films which contain the same proportion of Si-H2 bonds. The dangling bond spin density is somewhat lower in He/H films than in Ar/H2 deposited at the same rate, and decreases to about lx1016 cm-3 at high rf power.

Current materials technology provides methods for reducing solar cell panel temperatures aboard spacecraft by passive heat dissipation technicues. Technology is available for the replacement of conventional solar cell panel substrates with materials which combine the advantages of lighter weight, improved structural strength, and increased thermal conductivity. This study demonstrates how the application of such methods can significantly improve the photovoltaic efficiency of solar cell panels.

The density of states distributions near mid gap in a series of hydrogenated amorphous silicon films have been determined from space charge limited current measurements. The measurements were made on Au/aSi:H Schottky diode structures prepared by reactive rf sputter deposition. Samples with hydrogen concentrations near 16% as determined from infrared absorption had densities of states of 3x1014 states/cm3 eV. The experimental results indicate that high quality aSi:H films with low densities of states can be obtained under certain deposition conditions and that the density of states at mid gap is hydrogen concentration dependent with a minimum near 16%. For a given hydrogen concentration, films thicker than 2 um yielded the lowest density of states consistent with a model in which diffusion currents can be neglected and where surface and interface layers have a higher defect density than the bulk of the film.

We report for the first time the optical absorption and photovoltaic characteristics of thin films of Cu2SnS3,. Films obtained by the direct evaporation of the synthesised compound were observed to be deficient in copper, while those grown in an atmosphere of copper vapour were observed to be more stoichiometric. Both sets of films are characterised by indirect and direct absorption edge properties. The indirect absorption edges are at 1.O65 and 1.5O0 eV, while the direct band edges are at 1.658 and 1.770 eV for the copper deficient and stoichiometric films respectively. The stoichiometric film is characterised by p-type semiconducting properties while schottky type solar cell developed from it is observed to have promising photovoltaic characteristics.