Papers by Keyword: Charge Transport

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Authors: H.-E. Nilsson, E. Bellotti, K.F. Brennan, M. Hjelm
Authors: Migbar Assefa Zeleke, Lai Xin, Li Sheng Liu
Abstract: Modeling of heat and electrical current flow simultaneously in thermoelectric convertor using classical theories do not consider the influence of defects in the material. This is because traditional methods are developed based on partial differential equations (PDEs) and lead to infinite fluxes and stress fields at the crack tips. The usual way of solving such PDEs is by using numerical technique, like Finite Element Method (FEM). Although FEM is robust and versatile, it is not suitable to model evolving discontinuities since discontinuous fields are mathematically singular at the crack tip and required an external criterion for the prediction of crack growth. In this paper, we follow the concept of peridynamic (PD) theory to overcome the shortcomings above. Therefore, the main aim of this paper is to develop the peridynamic equations for the generalized Fourier’s and Ohm’s laws. Furthermore, we derived the peridynamic equations for the conservation of energy and charge for the coupled thermoelectric phenomena.
Authors: James R. Jennings, Qing Wang
Abstract: General characteristics of dye-sensitized nanoporous semiconductor electrode systems are summarized, with a particular emphasis on dye-sensitized solar cells. Properties of these electrode systems which distinguish them from conventional bulk semiconductor electrodes are highlighted. Current understanding of electron transport in dye-sensitized solar cells, in terms of the diffusion and multiple trapping models, is reviewed. Alternative transport and recombination theories are also briefly reviewed. Electron transfer at the semiconductor/electrolyte interface in dye-sensitized solar cells is reviewed and recent experimental results obtained by the authors are highlighted. As applicable, common techniques for characterization of electron transport and transfer in dye-sensitized solar cells are described, with reference to case studies where the electron diffusion length in dye-sensitized solar cells has been estimated. The steady-state aspects of the dye-regeneration process are also reviewed, together with the cross-surface percolation of holes in the dye monolayer and the finite-length diffusion of redox species in the electrolyte.
Authors: Guo Jun Kang, Chao Song, Xue Feng Ren
Abstract: A series of silicon (VI) porphyrins compounds with varying meso substitutions Si (TPP)Cl2 (where X=5,10,15,20-tetraphenylporphyrin), Si (TFP)Cl2 (X=5,10,15,20-tetrafluorenylporphyrin), Si (TQP)Cl2(X=5‚10‚15‚20-tetra (2,3,6,7-tetrahydro-1H,5H-benzo [ij] puinolizine) porphyrin),Si (TMP)Cl2(X=5,10,15,20-tetra (N,N-dimethylphenyl) porphyrin) have been investigated using density functional theory (DFT) to assess the influence of ruffled conformation on the electronic structures, frontier molecular orbital, charge carrier transport, electronic spectra. The electronic structures reveal that all these Si porphyrins display visible ruffling distortion, as the dihedral angle Cα2-N2-N4-Cα4 are ca. 30 ̊. And calculations confirm that ruffed distortion result in higher LUMO energies, lower EA values than corresponding planed Zn porphyrins, especial for similar λhole and λelectron values. These calculations suggest that the ruffled conformation bring about better charge injection and transport, which would broaden the application of distorted porphyrin in several different fields.
Authors: V.C. Anye, M.G. Zebaze Kana, Jing Du, Wole Soboyejo
Abstract: We examine the fundamental operation of an Organic Light Emitting Device with emphasis laid on the Hole Transport Layer (HTL) and the optoelectronic properties of the other layers that make up the device. Investigation of the adhesion properties together with surface morphology, electrical and optical characterization of the different layers of the device was carried out. Poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT: PSS) was used as the conventional HTL material in the first case. This yields the reference device or system under studies. In the second case, PEDOT: PSS was replaced by an inorganic material, molybdenum trioxide (MoO 3 ). The device performance in case two (2) revealed an improvement in performance. A couple of deposition techniques were examined together with the analysis of their effect on the resultant device properties. With the aid of theoretical models, we quantified the results obtained in terms of average pull-off forces and corresponding adhesion energies. The Derjaguin-Muller-Toporov model was utilized to model the adhesion energies between interfaces of adjacent layers of the device. Results that delineate modeling of charge transport across device interfaces are shown including the effects of pressure on the device optoelectronic properties.
Authors: Eugen R. Neagu, Rodica M. Neagu, José N. Marat-Mendes
Authors: L.A. Kosyachenko, I.K. Vereshchagin, S.M. Kokin
Authors: H.-E. Nilsson, U. Englund, M. Hjelm
Authors: B. Agyei-Tuffour, E.R. Rwenyagila, J. Asare, O.K. Oyewole, M.G. Zebaze Kana, D.M. O’Carroll, W.O. Soboyejo
Abstract: This paper explored the effects of pressure on contacts between layers of organic photovoltaic cells with poly (3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as the active layer. The contacts between the layers are modeled using analytical concepts and finite element models. The potential effects of surface roughness and dust particles are modeled along with the effects of lamination pressure and adhesion energy. The results show that, increased pressure is associated with decreased void length or increased contact length. The contacts associated with the interfaces between the active layer and the hole/electron injection layer poly (3,4-ethylenedioxythiophene: poly styrenesulphonate (PEDOT.PSS) and Molybdenum trioxide (MoO3) are also compared. The implications of the results are discussed for the design of stamping/lamination processes for the fabrication of organic photovoltaic cells.
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