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Availability of Liquid Crystalline Materials for Organic Polycrystalline Semiconductor Thin Films

Published online by Cambridge University Press:  26 February 2011

Hiroaki Iino  and
Jun-ichi Hanna
Hiroaki Iino
Affiliation:
iino@isl.titech.ac.jp, Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, J1-2, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
Jun-ichi Hanna
Affiliation:
hanna@isl.titech.ac.jp, Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, J1-2, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
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Abstract

We have investigated the charge carrier transport properties of polycrystalline films fabricated with discotic and calamitic liquid crystals. The polycrystalline films of these liquid crystals exhibiting particular textures under a polarized microscope, i.e., hexagonal and co-circular patterns for discotic and calamitic liquid crystals, respectively, which indicate that the molecular alignment in the liquid crystalline phase is well preserved exhibit clear hole transport along with molecular stacks even in a 15 μm thick film, judging from transient photocurrents by time of flight method. The hole mobilities are over 0.1 cm2/Vs at room temperature. These results indicate formation of fewer grain boundaries across conduction channels. On the other hand, the carrier transport properties in the polycrystalline films of non-liquid crystalline molecules with the same molecular shape exhibit no particular patterns as described and photocurrents are annihilated in the bulk as a function of time, indicating many deep trap sites in grain boundaries. The present results indicate that the liquid crystalline molecule is a good candidate for preparing quality organic polycrystalline semiconductor thin films in opto-electronic applications.

Keywords

organicphotoconductivitypolycrystal
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 965: Symposium S – Organic Electronics – Materials, Devices and Applications , 2006 , 0965-S08-10
Copyright
Copyright © Materials Research Society 2007

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