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

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) to1.9~2.0(Si 3 N 4 and ZnO) to1.72~1.75(SiON) to 1 (air). Experimental results show that the use of 0.4 μ m long ZnO NT arrays coated with a 150 nm thick SiON film increasesΔη/ηby 39.2% under AM 1.5 G (100 mW/cm 2 ) illumination as compared to that of regular SCs with a Si 3 N 4 /micropyramid surface. This enhancement can be attributed to SiON/ZnO NT arrays effectively releasing surface reflection and minimizing Fresnel loss.