Improving Crystalline Silicon Solar Cell Efficiency Using Graded-Refractive-Index SiON/ZnO Nanostructures

Abstract

The fabrication of silicon oxynitride (SiON)/ZnO nanotube (NT) arrays and their application in improving the energy conversion efficiency (η) of crystalline Si-based solar cells (SCs) are reported. The SiON/ZnO NT arrays have a graded-refractive-index that varies from 3.5 (Si) to 1.9~2.0 (Si3N4 and ZnO) to 1.72~1.75 (SiON) to 1 (air). Experimental results show that the use of 0.4 μm long ZnO NT arrays coated with a 150 nm thick SiON film increases Δη/η by 39.2% under AM 1.5 G (100 mW/cm2) illumination as compared to that of regular SCs with a Si3N4/micropyramid surface. This enhancement can be attributed to SiON/ZnO NT arrays effectively releasing surface reflection and minimizing Fresnel loss.