Angermann, H.; Laades, A.; Stürzebecher, U.; Conrad, E.; Klimm, C.; Schulze, T.F.; Lawerenz, A.; Korte, L.: Wet-chemical preparation of textured silicon solar cell substrates: Surface conditioning and electronic interface properties. In: 10th International Symposium on Ultra Clean Processing of Semiconductor Surfaces. UCPSS 2010. September 19 - 22, 2010, Ostend, Belgium, 2010, p. 113-114
Abstract:
Decisive preconditions to the development of economically attractive solar cells are further improvements of the energy conversion efficiency by appropriate interface preparation and passivation meth-ods as well as the reduction of material consumption by the application of thin-film technologies [ ]. For this purpose also the simplification of technological proc-esses, particularly the suitability and cost-effectiveness of wet-chemical cleaning and etching processes has to be taken carefully into consideration. This paper reports on the investigation of wet-chemical etching und surface conditioning of different Si sub-strates, carried out before preparation of thin oxides, amorphous / crystalline (a-Si:H/c-Si) hetero-junctions, Si nitride (a-SiNx:H) passivation layers and contacts.The relation between structural imperfections at Si surfaces, light trapping behavior, interface state densi-ties and recombination losses was investigated by scan-ning electron microscopy (SEM), surface photovoltage (SPV) [5], microwave detected photo conductance decay (µW-PCD) [ ], quasi-steady-state photo conduc-tance (QSSPC), and UV-NIR-reflectance measure-ments [ ]. Electronic interface properties of textured Si substrates for solar cells application were found to be mainly influenced by the crystallographic surface configuration of light-trapping structures and secondly, the effective-ness of wet-chemical smoothing, H-termination or oxidation procedures. Strong effects of surface conditioning were found on c-Si/a-Si:H, on Si carbide a-SiC:H and also on c-Si/a-SiNx:H interfaces, even though the field effect passivation is based on the band bending caused by a fixed charge in the film.