Incorporating photonic layers into polymer solar cells

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0933435MouleThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).SummaryIn this proposal, the PIs will determine whether monolayers of nanoparticles with tuned surface plasmon polaron (SPP) frequencies can be effectively used to increase the light absorption and thereby the power conversion efficiency (PCE) of solution processed organic photovoltaic devices (OPV). The proposed project has the following four Intellectual Merits components that will be addressed separately. 1) Synthesis of dielectric/metal core/shell colloids with tuned SPP resonance: In the synthesis component, metal nanoparticles and nano-shells will be fabricated with SPP energies that are tuned from 600 nm - 850 nm. The nano-shells will be fabricated with a SiO2 core and Au, Ag or Cu as the shell layer. The solubility of the colloids and electrical connection to surrounding OPV materials will be controlled using various conjugated surfactants. 2) Deposition of colloid monolayers over large areas: The colloid monolayers will be deposited over large areas using the spin coating technique. Prior UC Davis research has shown that well defined monolayers can be spin coated if the concentration, spinning speed, surface tension and surface adhesion are carefully controlled. 3) Characterization and modeling of colloid film optical properties: The optical properties of the colloid monolayers will be measured using variable angle spectroscopic ellipsometry (VASE) on a variety of substrates. The object of this step is to determine i) Whether light that is absorbed by SPP modes is dissipated thermally or does it dissipate by causing electronic excitation in the OPV materials? ii) If the SPP modes cause electronic excitations, in which direction, over what distance and in what spectral range? iii) What is the spectrum and intensity of light reflected and transmitted from a nano-shell monolayer in such a layer stack? iv) What proportion of the increased optical field in the OPV layers can be attributed to normal scattering and what part to the SPP modes? 4) Fabrication and testing of single and multiple band gap polymer photovoltaic devices incorporating the plasmonic waveguide layers: Tandem (two PV layers) OPV devices will be fabricated to determine if and how much the optical absorption can be increased using layers of photonic metal nanoparticle layers. The specific goal of the device studies is to enhance the absorption of low band gap OPV materials that absorb in the near infrared using the metal colloid monolayers. The broader impacts of this project are in the training of new professionals that are educated in the key area of photovoltaic technology. Special emphasis is placed in this project on supporting a graduate student that is a working mother.