Influence of hydrogen plasma treatment on Al-doped ZnO thin films for amorphous silicon thin film solar cells

Abstract

This study investigates the effects of H 2 plasma treatment on characteristics of Al-doped ZnO (AZO) thin films prepared by RF magnetron sputter at 200 °C for amorphous silicon (α-Si) thin film solar cell fabrication. Results of X-ray diffraction analysis showed that the structure of the plasma-treated film did not change but its crystallinity deteriorated as compared to that of the as-deposited film. The electrical resistivity of the AZO films decreased after H 2 plasma treatment, regardless of plasma power. The most improvements in the electrical and optical properties of the AZO film were obtained by applying H 2 plasma RF power of 50 W, where the film resistivity decreased from 1.23 × 10 −3 to 8.23 × 10 −4 Ω cm and the average optical transmittance in the wavelength range of 400–700 nm increased slightly from 89.5% to 91.7%. To enhance light trapping in solar cells, surface-textured AZO films were developed using diluted HCl etching and the haze ratio beyond 30% was obtained. Additionally, the α-Si thin film solar cells consisting of the prepared AZO thin film as the transparent electrodes were fabricated. The efficiency of the cell increased form 3.26% for the as-deposited AZO film to 5.14% for the 0.2%-HCl-etched and H 2 plasma-treated film.