Fabrication and characterization of holographic lenses recorded in photopolymers with high refractive index modulation for application in solar concentration

Holographic optical elements have a history of use in solar concentrating devices. One of the most significant challenges of using these elements in real-life devices is their typically high angular and spectral selectivity. A possible solution to expanding their operational range is using thinner devices, but to achieve high diffraction efficiency, a recording material with a high refractive index is required. In this work, a photopolymer with high refractive index modulation is used to create volume holographic lenses in layers as thin as 10 µm, while maintaining high diffraction efficiency. These lenses are designed for minimal angular selectivity, while still operating in the volume regime through modelling using the Kogelnik coupled wave theory. A theoretical analysis of the operation of the device as a volume holographic element was carried out. Once recorded, the full benefits of the low angular selectivity concentrating hologram are measured using a PV cell in a solar simulator and are compared with more angularly selective counterparts. An improvement of the PV cell performance of 44% is observed when coupling light with the thinner, less angularly selective lens.