Researchers led by Saudi Arabia’s King Khalid University have developed a 3D-printed anti-reflective coversheet for PV modules.
The cover sheet is based on cyclic-olefin copolymers (COC), to which a powder of aluminum oxide (Al2O3) was added at different concentrations. COC are polymers with exceptional mechanical characteristics and transparency, while Al2O3 is known for its enhanced anti-reflection properties.
“The application of antireflective materials on the photovoltaic substrates can enhance the absorption of sunlight and minimize the reflection,” explained the researchers. “Currently, there is no ideal anti-reflective coating for solar cells that can allow the transmission of sunlight without any reflection.”
The novel coversheet was 3D-printed with a size of 52 mm x 38 mm × 1mm and placed on polycrystalline silicon PV cells. The filament for the printer was created in-house by heating the COC polymer and Al2O3 until they reached a molten state. Then, the mixture passed via a spinnerette and later underwent a solidification process. Five filaments were created, one with pure COC and the other with 1 wt% (COCA 1), 2 wt%(COCA 2), 3 wt% (COCA 3), and 4 wt% (COCA 4) of Al2O3.
“Fused deposition modeling (FDM) is an additive manufacturing method that works on the principle of extrusion. A 3D coversheet design is created by a standard computer-aided design (CAD) software,” the team explained. “The specimens are produced by utilizing a nozzle having a diameter of 0.4 mm. The bed temperature is maintained at 60 C, the layer thickness is set at 0.2 mm, the raster angle is set at 45, and the infill pattern is linear without support.”
All the products were tested for structural and morphological behavior, mechanical characteristics, optical characteristics, external quantum efficiency (EQE) and internal quantum efficiency (IQE), spectral responsivity, electrical characteristics, and I-V characteristics.
The COCA3 coversheet was found to have the highest transmittance of 94.65% and lowest reflectance of 5.35%. The scientists also found that the reflectance increases at higher angles of incidence, from 5.35% at 0 C to 21.32% at 80 C for the COCA3 sample and transmittance decreases from 94.65% at 0 C to 78.68% at 80 C for the COCA3 sample. They also ascertained that the peak spectral responsivity increased from approximately 0.05 to around 0.58 A/W at 850 nm.
Furthermore, the testing showed that hall mobility and carrier concentration increased gradually as the electrical resistance decreased in the COCA3-covered cell. It was also found that the COCA3 coversheet has a lower electrical resistance, as well a higher hall mobility and carrier concentration.
“The power conversion efficiency of COCA coated photovoltaic cells was shown to increase from 13.74% to 18.34% under controlled conditions and from 12.88% to 17.21% under open air conditions up to a concentration of 3 wt% of alumina (COCA3),” the group concluded. “With the addition of alumina at a concentration of 4 wt%, both the open-circuit voltage and short-circuit current are reduced, which leads to a reduction in efficiency of the photovoltaic cell.”
Their findings were presented in “Enhanced photovoltaic efficiency through 3D-Printed COC/Al₂O₃ anti-reflective coversheets,” published in the Journal of Materials Research and Technology. Scientists from Saudi Arabia’s King Khalid University, India’s Kongu Engineering College, and Velalar College of Engineering and Technology have conducted the research.
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