Texture surfaces and etching mechanism of ZnO:Al films by a neutral agent for solar cells

Texture surfaces of ZnO:Al (AZO) films are prepared by ammonium acetate, a neutral etching agent. The structural, optical, and electrical properties of AZO films are investigated in detail for improving the light trapping ability. Under the optimal etching conditions (e.g., solution concentration of 5.0 wt% and etching time of 20 min), AZO films have a typical crater-like structure with haze values in the 20-30% range, as well as a high visible transparence and electrical conductivity. A feasible mechanism model is proposed to explain the etching process. Both H+ and OH− hydrolyzed in solution are involved in the etching reaction. The etching reaction and product diffusion co-dominate the process to form crater-like structures. In ammonium acetate, the etching process is much mild and controllable, making it easy to generate homogeneous texture morphologies in a large area. The high conversion efficiency of 10.75% is achieved for single-junction amorphous silicon thin-film solar cells using textured AZO films as the front contact layers. The ammonium acetate is an ideal etchant for preparing textured AZO films for commercial applications in solar cells.