Texture etched ZnO:Al coated glass substrates for silicon based thin film solar cells

ZnO:Al films were r.f.- and d.c.-magnetron sputtered on glass substrates from ceramic (ZnO:Al2O3) and metallic (Zn:Al) targets, respectively. The initially smooth films exhibit high transparencies (T greater than or equal to 83% for visible light including all reflection losses) and excellent electrical properties (rho = 2.7-6 x 10(-4) Omega cm), Depending on their structural properties these films develop different surface textures upon post deposition etching in diluted HCl. The light scattering properties of suitable films can be controlled over a wide range simply by varying the etching time. Moreover, the electrical properties are not affected by the etching process. Thus, within certain limits a separate optimization of the electro-optical and light scattering properties is possible. Amorphous silicon (alpha-Si:H) based solar cells prepared on these new texture etched ZnO-substrates show high quantum efficiencies in the long wavelength range demonstrating an effective light trapping. First alpha-Si/alpha-Si stacked solar cells were realized with initial efficiencies exceeding 10%. (C) 1999 Elsevier Science S.A. All rights reserved.