Modified Surface Texturing of Aluminium-Doped Zinc Oxide (AZO) Transparent Conductive Oxides for Thin-Film Silicon Solar Cells

Abstract

For thin-film solar cells, the properties of the front transparent conductive oxide (TCO) electrode is an important factor in determining the overall performance of the solar cells. An efficient light trapping scheme is required to increase the optical light path and thus enhance the photon absorption within the solar cells. Improved photon absorption is necessary to increase the short-circuit current density (Jsc) and thus the efficiency of cells. In this paper we report the results of the texturing of aluminium-doped zinc oxide (ZnO:Al or AZO) thin films for enhanced light scattering. AZO films were deposited onto soda-lime glass sheets by in-line DC magnetron sputtering. An effective AZO texturing method was developed using diluted hydrogen chloride (HCl) and hydrogen fluoride (HF) acids through either a two-step etching or a mixed etching process, which significantly improves the uniformity of the textured surface. Texturing based on HCl and HF combines the advantages of the large craters created by HCl etching and smaller jagged but uniform features resulting from HF etching. In this work, we demonstrate that by adopting the two-step or the mixed texturing method, it is possible to achieve high haze values of above 40% with very low surface roughness values. The combination of low surface roughness and high haze is beneficial to prevent shunting issues, and is thus very attractive for the fabrication of thin-film silicon solar cells.