Nanoscale optical antennas can modify the direction, decay rate and luminescence quantum efficiency (QE) of excitonic emission from organic semiconductors by concentrating optical modes into nanometer-scale volumes. Here, the emission properties of heterostructured optical antennas (fabricated by template-directed sequential electrodeposition) consisting of plasmonic (noble metal) nanowire antennas coupled to poly(3-hexylthiophene), P3HT, conjugated polymer disks (20 nm high; 60 nm diameter) are presented. The radiative decay rate (Tr) of P3HT in the presence of a single gold nanoantenna is determined to be 440 x 10^6 s^( -1) from photoluminescence lifetime measurements - an increase by a factor of 31 over P3HT in the absence of antennas. Both Tr and QE enhancements of up to 135 and 55 are shown to be possible in theory (full-field electromagnetic simulations), for plasmonic nanowire antennas with optimized length and diameter (180 and 40 nm, respectively) that resonate at the emission wavelength ofP3HT. Work is underway to characterize arrays of plasmonic nanoantennas coupled to 20 nm thick P3HT films to demonstrate large-area enhancements in Tr and QE. Benefits to the absorption characteristics ofP3HT thin films using silver nanoantennas with resonances tuned to the polymer absorption band will also be discussed. When incorporated onto the metallic electrode of bulk-heterojunction photovoltaic test devices the nanoantennas will be shown to render the electrode optically active resulting in improved red response in the photo current spectra.
Brief Bio: Deirdre O'Carroll is an Assistant Professor in Materials Science and Engineering and Chemistry at Rutgers University. She obtained her B.E. (Elec. Eng., 2002) and PhD (Microelectronics, 2008) at University College Cork and the Tyndall National Institute, Ireland. From 2007 to 2009 she was a postdoctoral researcher in the Atwater Group at California Institute of Technology and in 2010 she completed an EC Marie Curie International Outgoing Fellowship in the Ebbesen Group at the University of Strasbourg and CNRS. Research interests include: Photonic nanostructures, plasmonics, conjugated polymer nanostructur,e s and organic pbotonic devices.