Wet-chemical preparation of textured silicon solar cell substrates: Surface conditioning and electronic interface properties

摘要

The dominance of crystalline silicon (Si) in photovoltaics can be ascribed partly to the extensive knowledge about this material, which has been accumulated in microelectronics technology. Methods to passivate Si interfaces, which were developed for microelectronic device technologies, have been extended to solar cell manufacturing in the past. These methods, however, have been optimised for polished substrates, and do not work so effective with textured surfaces, which commonly used in the fabrication of high efficiency Si solar cells to enhance anti-reflection properties. Decisive preconditions to the development of economically attractive solar cells are further improvements of the energy conversion efficiency (η) by appropriate interface texturisation and passivation of interface defects, as well as the reduction of material consumption. For this purpose the simplification of technological processes, particularly the suitability and cost-effectiveness of wetchemical cleaning and etching methods has to be taken carefully into consideration. Wet-chemical processes are used in solar cell manufacturing mainly for three purposes: (1) removal of saw damage, (2) texturisation and (3) surface conditioning for the subsequent passivation and/or p/n junction and contact formation. This paper reports on investigations of wet-chemical texturisation und surface conditioning of different Si solar cell substrates, carried out before preparation of hydrogenated amorphous Si (α-Si:H)/c-Si, Si carbide (α-SiC:H)/c-Si, Si nitride (a-SiN_x:H)/c-Si hetero-junctions.