Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 29: [CPP] Organic Electronics and Photovoltaics I (Joint Session DS/CPP/HL/O)
O 29.10: Vortrag
Dienstag, 23. März 2010, 12:00–12:15, H37
Charge transport in conjugated polymers with energetic disorder — •James C Blakesley1,2, Helen S Clubb1, Christopher Groves1, Louise M Hopkins1, and Neil C Greenham1 — 1University of Cambridge, Cambridge, UK — 2Universität Potsdam, Potsdam, Germany
We investigate charge transport in sandwich-type devices with two polyfluorene-based copolymers: poly(9,9-dioctylfluorene-co-bis(N,N'-(4,butylphenyl))bis(N,N'-phenyl-1,4-phenylene)diamine) (PFB) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). A standard analysis of the data produces a poor fit to the data, with an apparent dependence of mobility on device thickness. Previously, such behaviour in electron transport has been attributed to trapping[1]. However, we find that a good fit is obtained by using a numerical simulation based on energetic disorder that takes into account the effects of electric field and carrier density on mobility (Extended Gaussian Disorder model). The amount of energetic disorder is quantified by 110+/-10meV and 100+/-10meV respectively. When the two materials are blended together, hole mobility remains constant when the fraction of PFB is 50% or greater, but drops dramatically for low concentrations of PFB. The amount of energetic disorder remains unaffected by any degree of blending, suggesting that there is no change in microscopic ordering of the polymers upon blending.
[1] R. Steyrleuthner, S. Bange and D. Neher, J. Appl. Phys. 105, 064509 (2009)