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French company Solarcloth tested and compared three colour solutions: MorphoColor interference films from the German Fraunhofer Institute; ColorQuant interference encapsulants from the German company Lenzing Plastics; and diffusion films from the Swiss company Solaxess.
French copper-indium-gallium-selenium (CIGS) photovoltaic cell specialist Solarcloth is looking to integrate colour into its flexible CIGS photovoltaic modules.
The company tested and compared three colour solutions: MorphoColor interference films from the German Fraunhofer Institute; ColorQuant interference encapsulants from the German company Lenzing Plastics; and diffusion films from the Swiss company Solaxess.
The companys CEO Alain Janet told pv magazine France that the technologies tested were selected based on seven main criteria, namely performance degradation, the impact of colorant materials on the product and the environment, reliability, angular color stability, cost, required inventory volume, and potential for industrial scale-up.
“Coloured PV is a fairly new playing field, where it is difficult to balance – to date – stability, cost in terms of industrial scale and customer expectations in terms of performance and visual appeal,” says Janet.
Fraunhofers MorphoColor solution is based on a stack of thin layers that allow for successive reflections, interferences and diffractions that result in an angular distribution of color in space. The stack is approximately 800 nm thick and can be deposited by pyrolytic sputtering onto a transparent polyethylene terephthalate (PET) substrate that can be integrated into the module between two layers of encapsulant.
“The efficiency losses generated are very low, around 6% of the original cell efficiency, even for white or grey films. We observed very good colour homogeneity and saturation using a black backsheet,” says Paul Rivas, a Nanoscience and Nanotechnology student, who conducted the study internally during his internship at SolarCloth. However, he explains that “the fragility of the PET substrate and the poor adhesion of the nanoprint tested in spring have delayed its application until the end of 2024.”
Lenzing Plastics’ ColorQuant interference encapsulants have shown very good interfilm and backfilm resistance. “But there is a clear mismatch between the colored front-side film and the front films used by SolarCloth. In addition, the low perceived color saturation is not very pleasing or very effective in hiding the cells,” says Janet.
The diffusion films from Solaxess, on the other hand, showed stable ageing and good aesthetics. However, their adhesion was poor and they showed significant performance losses, "especially in the light grey and white films."
The MorphoColor interference films from the German Fraunhofer Institute, with which SolarCloth has signed a development agreement, show the most promising results. “We are leaning towards this solution, subject to better adhesion and a competitive price for the MorphoFlex version,” said Janet, noting that the performance obtained is “very encouraging” and that the technique is “a little more expensive, but reasonable.” Once the solution has been validated, the modules will be directly “tinted” by SolarCloth. |
