An efficient antireflection coating (
ARC) can enhance solar cell performance through increased light coupling. Here, we investigate
solution-grown ZnO nanostructures as
ARCs for Si solar cells and compare them to conventional single layer
ARCs. We find that nanoscale morphology, controlled through synthetic chemistry, has a great effect on the macroscopic
ARC performance. Compared with a
silicon nitride (SiN) single layer
ARC, ZnO nanorod arrays display a broadband reflection suppression from 400 to 1200 nm. For a tapered nanorod array with average tip diameter of 10 nm, we achieve a weighted global reflectance of 6.6%, which is superior to an optimized SiN single layer
ARC. Calculations using rigorous coupled wave analysis suggest that the tapered nanorod arrays behave like modified single layer
ARCs, where the tapering leads to impedance matching between Si and air through a gradual reduction of the effective refractive index away from the surface, resulting in low reflection particularly at longer wavelengths and eliminating interference fringes through roughening of the air-ZnO interface. According to the calculations, we may further improve
ARC performance by tailoring the thickness of the bottom fused ZnO layer and through better control of tip tapering.