Using acrylamide-based photopolymers for fabrication of holographic optical elements in solar energy applications

Abstract

A holographic device is under development that aims to improve light collection in solar cells. The aim is to explore the potential of using photopolymer Holographic Optical Elements (HOE) to collect light from a moving source, such as the sun, and re-direct it for concentration by a holographic lens.. A working range of 45 degrees is targeted for such a device to be useful in solar applications without tracking. A photopolymer HOE is capable of efficiently re-directing light, but the angular selectivity of a single grating is usually of the order of one degree at the thicknesses required for high efficiency. The challenge here is to increase the angular and wavelength range of the gratings so that a reasonable number may be multiplexed and/or combined to provide a device that can concentrate light incident from a large range of angles. In this paper low spatial frequency holographic recording is explored in order to increase the angular and wavelength range of an individual grating. Ultimately, a combination of gratings will be used so that a broad range of angles of incidence are accepted. A design is proposed for the combination of such elements into a holographic solar collector. The first step in achieving this is optimization of recording at low spatial frequency. This requires a photopolymer material with unique properties, such as a fast monomer diffusion rate. This paper reports results on the efficiency of holograms recorded in an acrylamide based photopolymer at low spatial frequencies (100, 200 and 300 l/mm). The diffraction efficiency and angular selectivity of recorded holograms have been studied for various photopolymer layer thicknesses and different intensities of the recording beams. A diffraction efficiency of over 80% was achieved at a spatial frequency of 200 l/mm. The optimum intensity of recording at this spatial frequency was found to be 1 mW/cm 2 . Individual gratings and focusing elements with high efficiency and FWHM angles of 3 o are experimentally demonstrated.

Investigation of the sensitivity to humidity of an acrylamide-based photopolymer containing N-phenylglycine as a photoinitiator

“…Photopolymer materials can be used in holographic data storage [1][2][3][4][5][6][7], diffractive and refractive optical elements [8,9], solar concentrators [10,11], holographic interferometry [12][13][14][15][16] and holographic sensors [17][18][19]. Acrylamide-based photopolymers are widely covered in the literature.…”

Volume Holography: Novel Materials, Methods and Applications

“…HOEs are also capable to efficiently redirecting light with the aim to improve light collection in solar cells [42].…”

Characterization of volume holographic optical elements recorded in Bayfol HX photopolymer for solar photovoltaic applications

“…Two kinds of photosensitive materials proven to be suitable for the recording of holographic lenses as solar concentrators are dichromated gelatin (DCG) [5,[8][9][10][11] and photopolymers [12][13][14]. Both of these materials can be self-produced or acquired from manufacturing companies and provide high efficiency, resolution, index modulation and transparency.…”

“…Sam et al [12] used HoloMer 6A photopolymer, produced by Light Logics Holography and Optics, to record a holographic lens. Akbari et al [13] utilized self-produced acrylamide-based photopolymers for HOE recording in the frame of solar energy applications. They stacked together a combination of HOEs to achieve a broad angle range.…”