Abstract
► Silicon nanocone arrays show a total reflectance lower than 4% for wide spectral range. ► Large surface and SiNWs/Si interface recombination losses are identified responsible of the effective carrier lifetime degradation. ► Surface passivation is realized by rapid thermal oxidation which generates smooth surfaces for effective charge-carrier collection.
Uniform and regular silicon nanowires (SiNWs) arrays are fabricated on both sides of solar grade silicons (SiGS) by silver assist-electrochemical etching. SiNWs arrays exhibit an excellent antireflection character with an overall reflectance of 2% in the range from 300 to 1000nm. More importantly, the effective lifetimes of the symmetric SiNWs/Si structures decreased due to the high densities of dangling bonds and surface defects. Surface passivation to overcome lifetime degradation is realized by means of rapid thermal oxidation (RTO). Following rapid oxidation, Fourier Transform Infrared spectroscopy reveals that oxygen diffusion is enhanced inside silicon nanowires where the morphological structure is preserved during RTO. Moreover, it is shown that even the rapid thermal oxidation process is not effective to recover initial τeff due to the high density of imperfections involved during nanowires formation and the contamination level induced by silver. The interdiffusion between residual silver and metal contaminants in the core of the nanowire can probably limit the passivation effect due to the segregation of metal atoms at SiO2 and to the redistribution of both impurities across the wire.