Robert Collison - The City University of New York
Co-Author(s): Jacob Trevino, The City University of New York, Advanced Science Research Center, New York, NY; Stephen O'Brien, The City University of New York, City College, New York, NY; Vinod Menon, The City University of New York, City College, New York, NY; Adam Braunschweig, The City University of New York, Advanced Science Research Center and Hunter College, New York, NY
Plasmonic nanostructures can increase the photonic efficiencies of thin film solar cells by acting as optical antennae, by inhibiting the reflection of incident light off of the cell, and by coupling incident light into modes that propagate within the cell. These mechanisms effectively increase the optical density of the exciton-generating medium without increasing the physical thickness of the cell. For organic thin film cells, in which the transport of excitons or charge carriers to junctions or electrical contacts is often inhibited by energetic disorder and low mobilities, additional enhancement in performance may come from increasing the mobility of excitons. One approach is to optically couple organic excitons to delocalized photonic and plasmonic modes. Periodic arrays of plasmonic nanoparticles can be designed to support surface lattice resonances (SLRs), a type of propagating, delocalized plasmonic mode. The goal of this work is to fabricate SLR-supporting arrays of plasmonic particles coated with films of organic dyes, and measure and compare the properties of excitons in coupled and uncoupled films. We hypothesize that strong coupling to SLRs will increase the diffusion lengths of excitons within organic films coated onto the SLR supporting arrays.
We report on the fabrication and spectral characterization of fluorophore-doped polymers and dye aggregates deposited on top of 2D periodic arrays of gold nanoparticles on glass. First, periodic arrays of gold nanoparticles on glass chips were fabricated. The presence of SLRs was confirmed by the angle resolved reflection and transmission spectra of arrays. Coupling between the excitons of the dye molecules and the localized surface plasmon resonances (LSPRs) and surface lattice resonances (SLRs) of the gold particle arrays was investigated by measurement of their angle-resolved transmission and reflection spectra, and of the photoluminescence spectra and images of the organic exciton-coupled arrays. These data are analyzed to determine the degree of coupling and to elucidate the nature of the hybrid states, including their energy and dispersion relation. The effects of the exciton-plasmon coupling on the energy, diffusion length, lifetime, and decay pathways of the supramolecular dye excitons are assessed. From these results, the potential for SLR-supporting arrays to enhance the performance of organic thin film solar cells is discussed.
Funder Acknowledgement(s): The National Science Foundation, CREST IDEALS ; The City University of New York, Graduate Center ; The City College of New York ; The City University of New York, Advanced Science Research Center.
Faculty Advisor: Stetphen O'Brien, firstname.lastname@example.org
Role: I designed the plasmonic arrays (periodic arrays of circles, rectangles, and circle and bowties dimers), fabricated them using electron beam lithography methods, and characterized them optically by recording their angle-resolved transmission spectra. I also conjugated the arrays with dye-doped polymer films and characterized these systems by measurement of their angle-resolved transmission spectra and photoluminescence spectroscopy and microscopy.