Building-Integrated Concentrating Photovoltaics based on a low-toxicity photopolymer

Low-toxicity solar concentrator systems represent an important challenge for outstanding photovoltaic applications. Particularly, Multiplexed Holographic Lenses (MHL) as Holographic Solar Concentrators (HSC) provide insight into promising possibilities for Building-Integrated Concentrating Photovoltaics. This technology does not affect crucial ecosystems, and can convert buildings from energy consumers into energy suppliers. They can be used in windows, roofs, or walls, and a high diffraction efficiency and wide acceptance angle are desired. In this work, we presented several designs of multiplexed holographic lenses of low spatial frequency 525 lines/mm, based on a low-toxicity photopolymer and supported on a window glass. The average diffraction efficiency of these holographic solar concentrators was evaluated at 633 nm, whereas the acceptance angle was evaluated by measuring the short-circuit current under solar illumination at different incident angles. Versatile and high-efficiency holographic elements have been used to concentrate sunlight from different relative positions during the day, avoiding the need for expensive tracking systems. To the best of our knowledge, this is the best trade-off between high diffraction efficiency (85%) and wide acceptance angle (104◦) in a low-toxicity holographic solar concentrator.