Angermann, H.; Stürzebecher, U.; Kegel, J.; Gottschalk, C.; Wolke, K.; Laades, A.; Conrad, E.; Klimm, C.; Stegemann, B.: Wet-chemical conditioning of H-terminated silicon solar cell substrates investigated by surface photovoltage measurements. Solid State Phenomena 195 (2013), p. 301-304
In high-efficiency crystalline Si solar cells textured mono- and multi-crystalline substrates are commonly used to reduce reflection losses and to increase the absorption probability by light trapping. The improvement of the optical properties, however, is related to a larger effective surface area and to an increased surface micro-roughness. It inherently corresponds to an increased number of electrically active defect states in the band gap and thereby results in higher interface recombina-tion losses. Consequently, surface texturing has to be combined with appropriate surface passivation to minimise electronically active interface defects. This contribution reports on a very sensitive electrical method, namely field depended large signal surface photo voltage (SPV), which is utilised to detect the small number of defects in the range from 1010 cm 2eV 1 to 1014 cm 2eV 1. The capabilities of the large signal surface photovoltage (SPV) method for detailed investigations of interface recombination losses and the development of efficient interface passivation methods was shown for wet-chemical surface conditioning processes. Electronic interface properties of Si solar cell substrates were found to be mainly influenced by complete removal of saw damage and mini-mization of surface micro-roughness on different crystallographic surface configurations. The se-quences of wet-chemical oxidation, oxide removal and H-termination processes have to be carefully optimised with respect to the substrate configuration and subsequent deposition processes.