IEEE study presents novel microprism sheet that enhances performance of solar cells
Leveraging geometric optics principles, the proposed microprism sheets significantly enhances light absorption of thin-film photovoltaic sheets
image: The proposed microprism sheet, leveraging antireflection and light-trapping effect, enhances light absorption of thin-film photovoltaics on both sides, offering a path towards highly efficient photovoltaic technologies
Credit: “Glitter-size photovoltaics” by SandiaLabs on Openverse Image source link: https://openverse.org/image/4734b475-3455-43aa-a7c2-a8189aed3f0a?q=photovoltaic&p=9
In recent years, the development of photovoltaics (PV) or solar cells has increasingly focused on thinner and more transparent structures that facilitate thin film processing. Among them, semi-transparent thin-film PVs have gained considerable attention for their potential to be integrated into urban structures and vehicles.
Unlike conventional PVs that can harness only sunlight, semitransparent thin-film PVs can generate electricity from both outdoor sunlight and indoor artificial lighting, allowing light absorption from both front and rear sides of the films. On the other hand, these thin-film PVs have limited material volume for light absorption, resulting in insufficient sunlight capture and reduced efficiency. One solution to this issue is the integration of antireflective (AR) materials. However, conventional AR structures are difficult to integrate into thin-film PVs.
Addressing these challenges, a new study published in IEEE Journal of Selected Topics in Quantum Electronics (JSTQE) on April 25, 2025, introduced a novel large-area microprism sheet, made of polyethylene terephthalate (PET), that is geometrically designed to enhance light-trapping in thin-film PVs. “Our microprism sheets, based on principles of geometric optics, mitigate reflection losses on both sides of semi-transparent thin-film PV sheets, leveraging its light trapping effect,” explains Professor Jae-Hyun Kim from Kyung Hee University in South Korea. Due to its potential impact, the study was also featured in JSTQE’s Special Issue on Photonics for Climate Change Mitigation and Adaptation.
Typically, a thin-film PV module is covered with a protective encapsulation layer to shield it from environmental and mechanical damage. In this structure, light is lost mainly in two ways: through partial reflection at the air-cover interface and through internal reflection at the cover-PV boundary.
The proposed microprism sheet, comprising a wedge-shaped, teeth-like structure, exhibits a light trapping function, preventing not only initial reflection, but also redirecting a major portion of internally reflected light back to the PV cell. Specifically, the sheet leverages geometric redirection and internal reflections to prevent light from escaping. It also helps redirect most of the light incident from the rear surface back into the PV cell, maximizing light absorption. As a result, mathematical evaluations showed that the microprism sheet achieved the highest overall light absorbance when compared to an uncoated thin-film PV sheet and an AR-coated sheet.
In ray-optics simulations, an optimized microprism for amorphous-silicon PV sheet achieved 98% transmittance at all incident angles and redirected 81% of the internally reflected light back to the PV over typical solar incidence angles in mid-latitude regions. Furthermore, in outdoor experiments conducted with semitransparent thin-film perovskite (PVSK) PVs, the microprism sheet led to performance enhancements of 23% under front illumination, and 21% for rear illumination compared to an uncoated PV, owing to the combined AR and light-trapping effects.
“The improvements offered by our design will be key for next-generation solar cells,” remarks Dr. Kim. “Additionally, our microprism design allows significant modifications, such as integration with metal coatings to enable directional radiative cooling or for further improving efficiency.”
Overall, this innovative microprism approach demonstrates how simple geometric design can significantly improve light absorption and energy output in thin-film solar cells, paving the way for more efficient and versatile photovoltaic technologies.
Reference
Authors: Jae-Hyun Kim1, Geon-Tae Park1, Rira Kang2, So-Yeon Ju2, Semin Yu3, Byunghong Lee2, and Sun-Kyung Kim1
Title of original paper: Geometric Design for Light Trapping in Bifacial Thin-Film Photovoltaics
Journal: IEEE Journal of Selected Topics in Quantum Electronics
DOI: https://doi.org/10.1109/JSTQE.2025.3564549
Affiliations: 1Department of Applied Physics, Kyung Hee University, South Korea
2Electronic Devices Research Team, Hyundai Motor Group, South Korea
3PSC development Dept. Product Development Team 1, UniTest, South Korea