Fabrication of sub-wavelength antireflective structure to enhance the efficiency of InGaAs solar cells

Abstract

Large differences in the refractive index between semiconductors (Si, GaAs, etc.) and air produces considerable Fresnel loss, which can seriously hinder the absorption of sunlight by photovoltaic solar cells. This study presents a cost-effective roller nanoimprinting technique for the fabrication of sub-wavelength structures (SWSs) as an alternative to conventional anti-reflective coatings used to reduce reflectance in triple-junction InGaP/InGaAs/Ge solar cells. The proposed nanoimprinting technology uses a soft PDMS mold duplicated from a hard silicon template, which is fabricated using PS sphere lithography and dry etching processes. To evaluate the anti-reflective performance of SWSs, we employed rigorous coupled wave analysis (RCWA) to simulate the propagation of electromagnetic plane waves in a GaAs substrate. Simulation results demonstrated a considerable reduction in reflectance resulting from a gradual change in the refractive index provided by SWSs. Photoelectric conversion efficiency was also increased.