Effects of ZnO-nanostructure antireflection coatings on sulfurization-free Cu₂ZnSnS₄ absorber deposited by single-step co-sputtering process

ZnO nanostructures as anti-reflective coatings were synthesized by using hydrothermal technique for a sulfurization-free Cu₂ZnSnS₄ absorber prepared by co-sputtering deposition. By controlling the morphology of solution-grown ZnO nanostructures, the average reflectance of the Cu ₂ZnSnS₄ solar cell with branched ZnO nanorods decreased from 7.6% to 1.12%, and the energy conversion efficiency promoted by 10.4% from the initial value of 4.8% to 5.3%. The efficiency improvement was well studied with the effects of the gradually increased refractive index between the air and the top electrode of Cu₂ZnSnS₄ solar device, due to the presence of the ZnO nanostructure.