Experimental verification of spectral grating interference in multiplexed volume holograms employed as broadband dispersive elements for solar concentrators

Diffractive Spectral-Splitting Optical Element Designed by Adjoint-Based Electromagnetic Optimization and Fabricated by Femtosecond 3D Direct Laser Writing

“…Thus, our phase mask provides more flexibility in the position of the PV subcells over more traditional diffraction gratings that direct each color of light to a single diffracted order. 8 Spectral-splitting elements of this type have been previously investigated using a photoresist material and a direct binary search algorithm to optimize the pixel height levels. 12,13 However, heuristic optimization methods require a very large number of simulations of the structure before arriving at an optimal solution.…”

“…A separate spectral-splitting optical element disperses the wavelengths of the incident sunlight, so that different bands of the solar spectrum are directed to subcells of matching band gaps. Spectral splitting has previously been implemented with prisms, dichroic mirrors, multiplexed volume holograms, and specular reflection with highly selective interference filters . However, the design freedom offered by spectral splitting using planar dispersive diffractive optics is particularly attractive for large-area PV applications, in similar fashion to thin dielectric surfaces proposed for light management in PV cells …”

“…We note that this functionality involves both spectral dispersion and a mild amount of optical concentration, so that light incident on different positions of the phase mask are diffracted to different angles. Thus, our phase mask provides more flexibility in the position of the PV subcells over more traditional diffraction gratings that direct each color of light to a single diffracted order …”