Preparation and topography analysis of randomly textured glass substrates

Abstract

Randomly textured glass sheets in combination with a transparent conductive layer are promising as front contacts for silicon based thin-film solar cells. The authors have developed a novel method to create randomly textured glass surfaces. For the fabrication a wet chemically textured zinc oxide (ZnO) film is used as three dimensional etch mask and its surface topography is transferred to the glass substrate by ion beam etching. The typical texture of the sputtered and etched ZnO film exhibits craterlike features, which can be tuned by a variation of the initial ZnO film thickness and the etching time. Thus, the surface features of the resulting rough glass can be varied within a wide range. Its topography exhibits a maximum root mean square roughness of more than 200 nm with a lateral correlation length around 1500 nm. Microcrystalline silicon solar cells on the textured glass substrates show an increase of the short circuit current density by 36% compared to cells on flat glass. This proves the improvement of the so-called “light-trapping” effect in the solar cells by the glass texture.