Highly textured conductive and transparent ZnO films for HIT solar cell applications

Abstract

In this paper, aluminium-doped zinc oxide (AZO) thin-films were fabricated on both glass and silicon substrates by radio-frequency magnetron sputtering at various working pressures of 0.15–0.46 Pa. The effect of working pressure on the structural, electrical, and optical properties of the deposited AZO films was carefully studied. The lower working pressure is more favourable to large grain size, smooth surface, low electrical resistivity, and moderate optical transparency. For the AZO films deposited at lower working pressures, the larger grain size can be ascribed to the higher kinetic energy of the sputtered particles while the lower electrical resistivity is strongly related to both the presence of fewer grain boundaries due to the larger grain size and more activated amount of dopants in the films. We then applied AZO films deposited at 0.15 Pa to Al/AZO/n-a-Si : H/i-a-Si : H/p-c-Si/Al heterojunction Si solar cells with intrinsic thin layer (HIT) solar cells and achieved highly textured surfaces via acid etching. The HIT solar cells after acid texturing showed a higher external quantum efficiency (EQE) value than those with smooth AZO films mainly in the wavelength region from 300 to 500 nm, leading to an obvious increase in the conversion efficiency from 14.1% to 14.7%.