AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThM

Paper EM-ThM7
In-Plane Anisotropy of Pentacene Crystals on Surface Alignment Layers and its Influence on Photovoltaic and Thin-Film Transistor Device Characteristics

Thursday, November 16, 2006, 10:00 am, Room 2001

Session: Organic Electronic Materials and Devices
Presenter: A. Amassian, Cornell University
Authors: A. Amassian, Cornell University
A.C. Mayer, Cornell University
A. Kazimirov, Cornell University
D.-M. Smiglies, Cornell University
G.G. Malliaras, Cornell University
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Significant research effort has gone into understanding and controlling the growth of pentacene thin films, with the ultimate goal of enhancing charge transport by favouring 2D over 3D growth on surfaces. As pentacene behaves as a 2D powder on insulating surfaces, and electron transport is limited by charge trapping at grain boundaries, electron mobility can be further improved (in some directions) by orienting crystal growth using surface alignment layers. In this paper, we report on our recent efforts to induce in-plane anisotropy in pentacene crystals on a variety of mechanically rubbed surfaces, including conducting polymer (PEDOT:PSS) surfaces, high-k dielectrics (fluorinated ter-polymer) and various self-assembled monolayers (SAMs). In situ x-ray scattering measurements carried out at the Cornell high energy synchrotron source (CHESS) in a variety of measurement configurations show evidence of in-plane alignment in monolayer-thick pentacene films vacuum evaporated on some of these rubbed surfaces. Rubbing-induced preferential orientation of pentacene grains is shown to lead to an increase of the pentacene mobility by a factor of ~2.5 for current flow in the direction perpendicular to alignment in organic thin film transistor devices (OTFT).