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Russell J. Holmes
Ͻ 2014.11.21()  13:30~14:00
Enhanced exciton harvesting in organic photovoltaic cells by directly engineering intermolecular energy transfer
÷ ƼϿ_Holmes.pptx (96.34KB)  
     In this talk, we will discuss an alternate strategy that instead focuses on novel device architectures aimed at directly addressing the deficiencies in excitonic energy transfer that limit the exciton diffusion length (LD). Specifically we present an approach to engineer LD by optimizing the intermolecular separation in thin film and consequently, the photophysical parameters responsible for energy transfer. By diluting the electron donor boron subphthalocyanine chloride into a wide-energy-gap host, we optimize the degree of interaction between donor molecules and observe a ~50% increase in LD.  Interestingly, we find that dilution of the active material offers the ability to engineer energy transfer not only in the bulk, but also across interfaces. This is possible as dilution of one layer adjacent to a neat layer creates an imbalance of origin and destination sites for exciton hopping at the interface. Using a kinetic Monte Carlo formalism, we show that an imbalance of sites at interfaces can bias exciton motion toward the D-A interface, creating one-way gates for excitons. Thus, we demonstrate the ability to directly engineer exciton transport by tailoring intermolecular interactions in thin film, and also by designing exciton gating interfaces for enhanced exciton harvesting.