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|Title:||Engineering Interfaces in Polymer/ Fullerene Blends|
Department of Materials Science and Engineering.
|Abstract:||Polymer fullerene blends have gathered substantial interest in recent years for their potential technological applications, such as optoelectronics and photovoltaics. The performance of these blends is highly dependent on the properties of the nanoparticle-polymer, the polymer-polymer, and the air polymer interfaces. We first investigated the effect of processing additives on the morphology of active layer in polymer solar cell and improved the efficiency by controlling the interface region between active layer and electrode. In particular, polystyrene (PS) with different molecular weights (MW) are used as processing additives in poly[N-9?-heptadecanyl-2,7-carbazole-alt-5,5-(4?,7?-di-2-thienyl-2?,1?,3?-benzothiadiazole)] (PCDTBT)/ phenyl-C61-butyric acid methyl ester (PCBM) solar cell. The interfacial tension between PCDTBT and PS is increased with the increasing PS Mw, which enhances the segregation of the PS phase to the vacuum surface, where the interfacial area is decreased. The migration of PS to the surface mitigated the aggregation of PCBM in the active layer and thus optimized interface region between active layer and electrode, which led to higher efficiency. Secondly we studied the interfacial interaction between graphene or graphene oxide and poly(methyl methacrylate) (PMMA). The effects of graphene and graphene oxide on the dewetting dynamics of thin polymer films are also investigated. The results indicated that graphene oxide were much more effective than graphene in stabilizing the films against dewetting. The influence of graphene and graphene oxide on the interdiffusion of PMMA films was measured by neutron reflectivity. The diffusion coefficient was unaffected by the presence of graphene but was reduced with graphene, indicating that interactions between the PMMA and graphene were weaker than that between the PMMA and graphene oxide. Finally, eletrospining method is applied to prepare poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/ polyvinylpyrrolidone (PVP)/PCBM fibers for solar cell devices. By incorporation the fibers into active layer, multiple donor-acceptor interfaces are created in the fibers and in the backfill layer. Compared with the thin-film counterpart, the short-circuit current density and the fill factor are both enhanced in nanofiber-based systems, which is attributed to the favorable morphology provided by the fibrous network serving as a template for the active layer.|
|Appears in Collections:||Stony Brook Theses and Dissertations Collection|
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