Identifying effects of TiO2 nanowires inside bulk heterojunction organic photovoltaics on charge diffusion and recombination

Abstract

The charge carrier dynamics of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) organic bulk-heterojunction photovoltaics with and without TiO₂ nanowires are studied. Using inorganic nanowires as electron transport pathways improves the charge transit time and electron diffusion coefficient, which is the origin of fill factor and power conversion efficiency improvement observed in these devices. Through further comparison of devices with surface-modified nanowires (PCB–TiO₂-NW), it is found that under AM 1.5 light illumination, charge recombination is dominant in the organic layer rather than at the TiO₂ nanowire surface.