Optical Waveguide Lattices with Novel Transmission Properties Towards Enhanced Energy Conversion in Solar Cells

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This grant supports research that contributes to new knowledge related to optical materials for increased solar energy capture, thereby promoting progress in renewable, clean energy. The proposed optical structure consists of periodic arrays of light collecting elements created in polymer materials. The polymer consists of a blend of components that are synthetically organized into periodic structures that can control light transmission. When coated over a solar cell, this structure promises to convert more light into electricity. This would result in the generation of more power as compared to current solar cells, as well as mitigation of energy losses that have persisted in solar cell technologies. This material structure is also a low-cost alternative to more complicated and costly solar cell coatings. This award supports fundamental research on the structure-property relationships of this new material structure, particularly on how it collects light, as well as fundamental property-function relationships to increase energy conversion in solar cells. Studies of light transmission and solar cell output are performed, with optical simulations used to confirm experimental findings. The award also supports the education of high school and undergraduate students and helps broaden participation of underrepresented groups in research.Broadband optical waveguide lattices show the capability of collecting light from a broad angular incident range and transmitting it in a single direction. This capability to control light collection and transmission is attractive as a potential strategy to meet the critical need to manage light propagation and collection in optical devices, such as for increasing energy conversion and reducing losses in industry-standard front contact solar cells. The goal of this project is to prepare, characterize, and study multiple waveguide lattices created in polymer thin films as solar cell coatings, with the experimental objective to demonstrate a wide angular collection window for light, to thereby increase energy conversion. The structures are produced through irradiation of a photoreactive binary component polymer blend with arrays of microscale optical beams, which in turn form multiple arrays of broadband cylindrical optical waveguides. This research elucidates structure-property correlations between the waveguide lattices and their light transmission and collection characteristics, as well as investigates increases in external quantum efficiency and current density in front contact silicon solar cells when the structures are employed as the encapsulation layer. Such correlations are established by carrying out angle-resolved transmission and energy conversion measurements over the full solar spectrum and as a function of the waveguide lattice parameters, as well as through corroborative theoretical studies of light transmission using Beam Propagation simulations. This research promises to advance the capability to control the optical transmission properties of materials, with the potential to increase solar energy conversion, thereby advancing renewable, clean energy production. The educational activities of this award will seek to enhance high school education by providing research experiences, as well as advancing undergraduate education in materials science through interactive experiments. Education and recruitment efforts will focus on groups underrepresented in STEM.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.