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- Jonsson, Jacob, et al.
(författare)
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Angle-dependent light scattering in materials with controlled diffuse solar optical properties
- 2004
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 84:1-4, s. 427-439
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Tidskriftsartikel (refereegranskat)abstract
- Light scattering plays a prominent role in a wide range of energy-efficient materials and solar applications. Some examples are materials for daylighting, diffusely reflecting sunscreens, foils for radiative cooling and nanocrystalline solar cells. Measurements of the angular profile of light scattering are very useful for obtaining a detailed characterization of the light scattering mechanisms. We review recent theoretical results on the forward and backward light scattering profiles. Forward scattering is of major importance for novel pigmented polymeric daylighting materials. Measurements of scattering profiles are in good agreement with Mie theory. Backscattering profiles from highly diffusely reflecting paints containing titanium oxide-based pigments have also been measured. It seems that scattering from the paint surface dominates at low pigment volume fractions. Results for paints with high pigment volume fractions are interpreted in terms of coherent backscattering effects from the pigment particles.
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- Jonsson, Jacob, 1974-
(författare)
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Optical Characterisation of Miniature Structures and Translucent Sheets for Daylighting Applications
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For a long time spectrophotometry has been a powerful method of determining optical material properties. Since the technique measures the parameters of interest, reflectance and transmittance, it is in general easy to use and interpret. Certain materials, such as miniature structures or scattering materials, must be given a more careful analysis to avoid incorrect interpretation. General solutions to measurement challenges for thick scattering samples and anisotropically scattering samples are presented.Thorough knowledge about the components of a spectrophotometer gives a solid base which is necessary when trying to design or modify an instrument for the characterisation of miniature components. Focusing optics and pinhole apertures are two methods investigated for studying samples on a millimeter scale. Focusing optics retain a high intensity but might cause internal reflection. Pinhole apertures are easy to build into a sample holder, but they will reduce light intensity which can give problems with signal to noise ratio. Using a microscope as a focusing lens system permits the measurement of samples of a size down to the order of ten micrometers. However, absolute measurements are difficult due to the strong focusing properties of the microscope.Translucent sheets are of interest for daylighting applications, a growing field in today's energy-conscious society. If sunlight is to be used for indoor illumination it is preferable to make it diffuse. By using Transparent Refractive Index Matched Micro (TRIMM) particles in a transparent polymer sheet, it is possible to obtain high transmittance in combination with tailorability of the scattering profile. Such sheets have been characterised experimentally, as well as by Monte Carlo raytracing simulations. The good agreement between simulation and experiment shows that this type of simulation can be used in the materials design process. A more theoretical study of patterns in multiple Mie scattering has been carried out using the Monte Carlo program developed for characterisation of the TRIMM particle sheets.
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