College of Natural and Computational Sciences

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Browsing College of Natural and Computational Sciences by Author "Abadi, Asefa"

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    Studies of Novel Graphene Nanoribbon/ Polyaniline Nanocomposites for Their Applications in Solar Cells
    (Addis Ababa Universty, 2012-03) Abadi, Asefa; Mazher, Javed (Professor)
    Organic polymer nanocomposites blended with graphene nanostructures have recently attracted lot of scientific interest due to their novel heterojunction charge transport properties and for fabrication of solar cells with enhanced energy conversion efficiencies. Simulational studies of electronic and transport properties of polyaniline-graphene nanoribbon (PAn-GNR) nanocomposite systems have been performed in various conformations and in strict percolation regime. Ab-initio DFT-LDA-NEGF simulations have been carried out for at least seven compositionally vivid samples of the PAn-GNR system with built-in two-probe device geometries. As obtained density of states (DOS) and transmission spectra [T(E)] plots are examined for the charge transport behavior in these nano-systems. We have observed significant number of contributing states driven from contact electrodes in to the nanomaterial, which are described on the basis of Fano effects and as induced strong couplings. We have also studied electron and hole eigenstate conduction channels along with I–V measurements using Landauer relations for these nanocomposites which help in understanding different modes of the charge transport. For some of the samples we have observed a negative differential resistance (NDR) phenomenon which is rightly explained. Diagnoses of the NDR phenomena in respect to presence of Fano states and other DOS and transmission singularities have been conceded. Prospects of self-aligned PAN-GNR nanocomposites for solar cell applications have also discussed. The present study of nano devices would be helpful in understanding intrinsic properties of photovoltaic materials in nano-devices for their futuristic deployment in nano-solar cells.