Analysis of Photoelectronic Response in Semiconductor Nanowires

This paper reports an analytical and simulation study of the photoresponse of semiconducting nanowires, focusing on photoconductivity and minority carrier diffusion characteristics. Fully depleted nanowires are found to give rise to ultra-high illuminated-to-dark conductivity ratio, as has been observed experimentally. Nanowires can also achieve reduced recombination rate and extended minority carrier lifetime. Band bending via surface fermi level pinning or doping engineering provides physical separation of electrons and holes, which can lead to significantly enhanced recombination lifetime. It is shown that nanowire photo-induced conductivity can be increased by > 10X over similar bulk structures under the same illumination level. A 30X enhancement in recombination lifetime can result with properly engineered energy bands, which is highly beneficial for the energy conversion efficiency of nanowire photovoltaic devices or nanowire/polymer solar cells.