Optimization of the texturization of ZnO:Al surface using HCl + HNO3 for application in thin film silicon solar cells

Abstract

As-deposited sputtered ZnO:Al (AZO) films exhibit high transparency (T ≥ 85% at 550 nm of wavelength) and excellent electrical properties (ρ = 2.58 × 10−04Ω cm). But the effective light scattering from the as deposited flat ZnO:Al substrate was not suitable for light trapping in thin film solar cells. Thus we used etching process by equi-molar HCl and HNO3 acid mixture on AZO substrates. The scattering properties of the films can be controlled simply by varying etching time. The electrical properties of the films are not affected much by the etching process, but the haze of the films varied form ~ 2% to ~ 30% at 550 nm of wavelength. These substrates have been used for the fabrication of amorphous silicon solar cells. Solar cells fabricated on etched AZO substrates, we have achieved 12.2% increase in conversion efficiency from the as-deposited AZO substrates.