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

This study investigates the effects of H2 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 H2 plasma treatment, regardless of plasma power. The most improvements in the electrical and optical properties of the AZO film were obtained by applying H2 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 H2 plasma-treated film.

► We examine the effects of H2 plasma treatment on characteristics of ZnO:Al films. ► H2 plasma treatment does not change the crystal structure of ZnO:Al films. ► The electrical resistivity of ZnO:Al films decreases after H2 plasma treatment. ► H2 plasma treatment increases slightly transmittance of AZO films in visible range. ► H2 plasma-treated AZO films enhance the efficiency of Si thin-film solar cells.