TY - JOUR TI - Synthesis and functionalization of gold nanorods for probing plasmonic enhancement mechanisms in organic photovoltaic active layers DO - https://doi.org/doi:10.7282/T30G3H7D PY - 2014 AB - Incorporation of plasmonic nanostructures into organic photovoltaic solar cells (OPVs) is proposed to address photovoltaic losses within these devices, such as radiative and non-radiative charge recombination, and insufficient light trapping. Plasmonic nanostructures are sub-wavelength antennae that harness light energy through localized surface plasmon resonances (LSPRs), providing energy-specific light management through far-field Rayleigh-scattering. Furthermore, induction of LSPRs produces high electric fields local to the nanostructure, which have been shown to enhance absorption and emission in fluorescent organic molecules; both manifestations of plasmon resonance are expected to enhance OPV performance through increased light-trapping, and active layer absorbance or emission, respectively. Herein, we employ the aspect ratio-dependent longitudinal-LSPR (L-LSPR) of gold nanorods to investigate plasmonic enhancement in OPVs. In this dissertation, gold nanorods (Au NRs) are fabricated by a seed-mediated synthesis. Methods are developed to provide L-LSPRs between 667 nm and 1018 nm using identical growth conditions; altering aspect ratio is performed by controlling the introduction time of the co-surfactant benzyldimethylammonium chloride (BDAC) to the NR growth reaction. The time-dependent influence of BDAC on Au NR aspect ratio is most evident during early times of NR growth (0-20 minutes), directly correlating to growth stages which are susceptible to epitaxial micellar adsorption and passivation of the growing crystalline facets. Analysis of Au NR morphology indicate that increased aspect ratio is brought about through BDAC’s inhibition of Au adatom adsorption to longitudinal facets, and a simultaneous increase in adatom adsorption to tip facets. A series of Au NRs are then fabricated, functionalized, and dispersed within poly (3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT: PCBM) bulk-heterojunction active layers. Au NRs with L-LSPRs of varying spectral overlap with the absorption and emission bands of the electron donor’s (P3HT) spectrum are prepared, in order to probe far-field and near-field enhancement mechanisms. OPV devices are fabricated from the nanoparticle-active layer composites, and their photovoltaic performance characterized. Substantial improvements in power conversion efficiency, up to 30%, are reported. Device performance increases with increasing L-LSPR wavelength. Evidence of plasmonic enhancements is not explicit; increased efficiency is attributed to improvements in molecular ordering of P3HT, as indicated by grazing incidence x-ray diffraction studies. KW - Materials Science and Engineering KW - Solar cells KW - Nanostructured materials KW - Photovoltaic power generation LA - eng ER -