| 1. |
- Cardona, M., et al.
(author)
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Ellipsometric investigations of piezo-optical effects
- 1998
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 313-314, s. 10-17
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Journal article (peer-reviewed)abstract
- An introduction to the stress-induced birefringence of solids, with emphasis on cubic and amorphous materials, is given. Most available experimental data have been obtained in the frequency region below the electronic absorption edge: the corresponding coefficients of the stress-optical tensor are then real. Above the edge (and also in the IR region of the Reststrahlen) they become complex. Ellipsometry is an excellent tool for the investigation of complex stress-optical functions. It also yields the hydrostatic pressure induced changes in the dielectric functions. Data obtained recently for diamond and zincblende-type crystals and their theoretical interpretation are discussed.
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| 2. |
- Granqvist, C. G., et al.
(author)
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Progress in Smart Windows Research: Improved Electrochromic W Oxide Films and Transparent Ti-Ce Oxide Counter Electrodes
- 1996
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In: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 8:1-4, s. 97-106
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Journal article (peer-reviewed)abstract
- We review recent work on sputter deposited W-oxide-based films. Improved electrochemical durability was obtained by electron bombardment during deposition, and enhanced coloration/bleaching dynamics was obtained by fluorination. Spectrally resolved scattering measurements indicated that haze levels ≪ 1 % could be reached. Oblique angle deposition could yield angular selectivity. New results are given for sputtered Ti-Ce oxide films, showing their capacity as counter electrodes in transparent electrochromic devices.
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| 3. |
- Granqvist, C.-G., et al.
(author)
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Recent advances in electrochromics for smart windows applications
- 1998
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In: Solar Energy. - 0038-092X .- 1471-1257. ; 63:4, s. 199-216
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Journal article (other academic/artistic)abstract
- Electrochromic smart windows are able to vary their throughput of radiant energy by low-voltage electrical pulses. This function is caused by reversible shuttling of electrons and charge balancing ions between an electrochromic thin film and a transparent counter electrode. The ion transport takes place via a solid electrolyte. Charge transport is evoked by a voltage applied between transparent electrical conductors surrounding the electrochromic film/electrolyte/counter electrode stack. This review summarizes recent progress concerning: (i) calculated optical properties of crystalline WO3, (ii) electrochromic properties of heavily disordered W oxide and oxyfluoride films produced by reactive magnetron bias sputtering, (iii) novel transparent reactively sputter-deposited Zr-Ce oxide counter electrodes and (iv) a new proton-conducting antimonic-acid-based polymer electrolyte. Special in depth presentations are given on elastic light scattering from W-oxide-based films and of electronic band structure effects affecting opto-chronopotentiometry data in Zr-Ce oxide. The review also contains some new device data for an electrochromic smart window capable of very high optical transmittance.Electrochromic smart windows are able to vary their throughput of radiant energy by low-voltage electrical pulses. This function is caused by reversible shuttling of electrons and charge balancing ions between an electrochromic thin film and a transparent counter electrode. The ion transport takes place via a solid electrolyte. Charge transport is evoked by a voltage applied between transparent electrical conductors surrounding the electrochromic film/electrolyte/counter electrode stack. This review summarizes recent progress concerning: (i) calculated optical properties of crystalline WO3, (ii) electrochromic properties of heavily disordered W oxide and oxyfluoride films produced by reactive magnetron bias sputtering, (iii) novel transparent reactively sputter-deposited Zr-Ce oxide counter electrodes and (iv) a new proton-conducting antimonic-acid-based polymer electrolyte. Special in depth presentations are given on elastic light scattering from W-oxide-based films and of electronic band structure effects affecting opto-chronopotentiometry data in Zr-Ce oxide. The review also contains some new device data for an electrochromic smart window capable of very high optical transmittance.
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| 4. |
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| 5. |
- Granqvist, Claes-Göran, et al.
(author)
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Towards the smart window : progress in electrochromics
- 1997
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In: Journal of Non-Crystalline Solids. - 0022-3093 .- 1873-4812. ; 218, s. 273-279
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Journal article (peer-reviewed)abstract
- Electrochromic devices have the ability to produce reversible and persistent changes of their optical properties. The phenomenon is associated with joint ion and electron transport into/out of an electrochromic thin film, in most cases being a transition metal oxide. This paper outlines the various applications of such devices in smart windows suitable for energy-conscious architecture, in variable-reflectance mirrors, and in display devices. Critical materials issues and design concepts are discussed. The paper also covers two specific research topics: computed electronic structure of crystalline WO3 incorporating ionic species, showing how reflectance modulation emerges from a first-principles calculation; and Li+ dynamics in heavily disordered Ti oxide, illustrating how diffusion constants derived from impedance spectroscopy can be reconciled with the Anderson—Stuart model.
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| 6. |
- Kullman, L., et al.
(author)
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Elastic Light Scattering and Electrochemical Durability of Electrochromic Tungsten-oxide-based Films
- 1996
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 288:1-2, s. 330-333
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Journal article (peer-reviewed)abstract
- Electrochromic W-oxide-based films were produced by reactive d.c. magnetron sputtering. Fluorination and substrate bias were used to modify the film properties. Spectral measurements of the total and diffuse light scattering showed that the diffuse component remained at much less than 1% in the visible, irrespective of electrochemical degradation, which is low enough for smart windows applications.
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| 7. |
- Lastras-Martínez, L. F., et al.
(author)
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Reflectance difference spectroscopy of GaAs asymmetric surface quantum wells above the fundamental gap
- 1998
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In: Physica status solidi. A, Applied research. - 0031-8965 .- 1521-396X. ; 170:2, s. 317-321
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Journal article (peer-reviewed)abstract
- We report Reflectance Difference (RD) measurement on (001) GaAs surface quantum wells (QW) under Ultra High Vacuum (UHV) conditions from 1.7 to 5.0eV. The QW is embedded between an arsenic-rich reconstructed GaAs surface and an AlAs barrier. The samples, grown by MBE with a protective arsenic cap layer, were heated to 320 and 430°C to desorb the As layer and form c(4 x 4) and (2 x 4) surface reconstructions, respectively. By modifying the surface reconstructure, we are able to separate the contributions to the optical anisotropy from the surface region (mainly associated with the As dimers) from those originating below the surface.
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| 8. |
- Lindström, T., et al.
(author)
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Electrochromic control of thin film light scattering
- 1997
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In: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 81:3, s. 1464-69
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Journal article (peer-reviewed)abstract
- Total and diffuse reflectance spectra were measured on Al surfaces covered with electrochromic W oxide films in colored and bleached states. Vector perturbation theory was used for analyzing the spectra. The diffuse reflectance appeared to originate from correlated (uncorrelated) interface roughness when the W oxide film was fully colored (bleached). Assuming partially correlated interfaces led to agreement between experimental and calculated spectra. The use of an electrochromic film appears a promising method to control the relative contributions of the interfaces to the resulting scattering.
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| 9. |
- Nostell, P, et al.
(author)
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Single-beam integrating sphere spectrophotometer for reflectance and transmittance measurements versus angle of incidence in the solar wavelength range on diffuse and specular samples
- 1999
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 70:5, s. 2481-2494
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Journal article (other academic/artistic)abstract
- A multipurpose instrument for the measurement of reflectance and transmittance versus angle of incidence for both specular and diffuse samples in the solar wavelength range has been constructed and evaluated. The instrument operates in the single-beam mode and uses a common light source for three experimental setups. Two integrating spheres, 20 cm in diameter, are used for diffuse transmittance and reflectance measurements. The transmittance sphere can be turned around an axis through the sample to vary the angle of incidence. The reflectance sphere uses a center mounted sample and a special feature is the position of the detector, which is mounted on the sample holder at the center of the sphere. This way the detector always sees the same part of the sphere wall and no light can reach the detector directly from the sample. The third setup is an absolute instrument for specular samples. It uses a small averaging sphere as a detector. The detector is mounted on an arm which rotates around the center of the sample, and it can thus pick up both the reflected and transmitted beams including all multiply reflected components. The averaging sphere detector is insensitive to small side shifts of the detected beams and no multiple reflections between detector and optical system occur. In this report a number of calibration procedures are presented for the three experimental setups and models for the calculation of correct transmittance and reflectance values from measured data are presented. It is shown that for integrating sphere measurements, the geometry of the sphere and the diffusivity of the sample as well as the sphere wall reflectance and port losses are important factors that influence the result. For the center mounted configuration these factors are particularly important and special emphasis is given to the evaluation of the reflectance sphere model. All three instrument setups are calibrated using certified reference materials and nonscattering mirrors and substrates. The results are also compared to the results of a double-beam Beckman integrating sphere for near normal angles of incidence and Fresnel calculations. The results in this article show that good agreement is obtained between results from the different instruments if, and only if, proper evaluation procedures are applied to the measured signals.
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| 10. |
- Rönnow, Daniel, et al.
(author)
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Correction Factors for Reflectance and Transmittance Measurements of Scattering Samples in Focussing Coblentz Spheres and Integrating Spheres
- 1995
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 66:3, s. 2411-2422
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Journal article (peer-reviewed)abstract
- The detector signals from a total integrated scatter (TIS) instrument, which uses a focusing Coblentz sphere, have been evaluated. Models for the calculation of correct reflectance and transmittance values for both scattering and nonscattering samples are presented. In particular, the correction for multiple reflections between sample and detector, the detector efficiency versus angle of incidence, and the symmetry properties of the Coblentz sphere have been investigated. Experimental results are compared with results obtained with an integrating sphere using a model for the correction of sphere asymmetry. The results show that the transmittance and reflectance values obtained with the TIS instrument and the integrating sphere agree only when the presented correction factors are properly taken into account.
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