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Holographic solar concentrators stand to benefit from the low angular selectivity and high diffraction efficiency that comes with thin layers and a high refractive index modulation (RIM); as lower angular selectivity reduces the need for solar tracking. While RIM is significant in the development of effective solar concentrating devices there are other important properties like material chemical stability, physical robustness and sensitivity to atmospheric conditions that must be considered. Recent developments have put forward a photosensitive sol gel glass material that meets the criteria of physical and chemical stability with low sensitivity to its environment and reported RIM of 0.003. In this investigation the RIM of a robust photopolymerisable sol-gel glass with a high dynamic range and fast curing times is improved using a thermal post processing method during a post exposure diffraction efficiency growth process. This process was done to maximise the achievable refractive index modulation, and so, many optimisations including exposure time, wavelength, and post processing temperature were made. This was done for different holograms recorded at many different spatial frequencies (400 – 1000 l/mm) and thicknesses. Improvements of 200% to the RIM were observed in some holograms after thermal post processing compared to holograms that were not treated. The max RIM values achieved using this method was 0.0055. Bragg curves were modelled based on the highest achievable RIM in order to determine the minimum thickness value that would provide close to 100% diffraction efficiency while minimising angular selectivity. These holograms were then recorded to showcase the materials’ potential as a solar concentrator.
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