Fig. 5: HDSG coating on thin-film crystalline silicon (c-Si) solar cells for improved efficiency, mechanical robustness, and oil-based self-cleaning performance.

a Schematic illustration of the HSG/HDSG film fabrication process on thin crystalline silicon (c-Si) solar cells. b 3D schematic cross-section of the final device structure, illustrating the layered configuration of the thin c-Si solar cell and HSG/HDSG coatings. c Current density–voltage (J–V) characteristics of solar cells with and without microstructured films. Inset: photographs of the fabricated devices. d External quantum efficiency (EQE) spectra of the same devices, showing spectral enhancements. Inset: schematic illustrating the microlens effect of HDSG domes that redirect light into the absorber layer. e Photographs of the flexible thin c-Si solar cell with HDSG films, showing bending radius of 1.5 cm. f Normalized photovoltaic parameters (Voc, Jsc, FF, and efficiency) as a function of bending cycles, confirming mechanical durability. g Optical images comparing self-cleaning ability. After contamination and rinsing, the HDSG-coated cell shows effective contaminant removal, while the flat reference remains fouled. h Relative Jsc/Jsc₀ before and after contamination, and after repeated rinsing, demonstrating superior self-cleaning performance of the HDSG-coated device. All scale bars in this figure represent 1.5 cm.