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Order Induced Charge Carrier Mobility Enhancement in Columnar Liquid Crystal Diodes

Eccher, Juliana and Faria, Gregório C. and Bock, Harald and von Seggern, Heinz and Bechtold, Ivan H. (2013):
Order Induced Charge Carrier Mobility Enhancement in Columnar Liquid Crystal Diodes.
In: ACS Applied Materials & Interfaces, 5 (22), American Chemical Society, pp. 11935-11943, ISSN 1944-8244,
[Online-Edition: http://doi.org/10.1021/am403681q],
[Article]

Abstract

Discotic molecules comprising a rigid aromatic core and flexible side chains have been promisingly applied in OLEDs as self-organizing organic semiconductors. Due to their potentially high charge carrier mobility along the columns, device performance can be readily improved by proper alignment of columns throughout the bulk. In the present work, the charge mobility was increased by 5 orders of magnitude due to homeotropic columnar ordering induced by the boundary interfaces during thermal annealing in the mesophase. State-of-the-art diodes were fabricated using spin-coated films whose homeotropic alignment with formation of hexagonal germs was observed by polarizing optical microscopy. The photophysical properties showed drastic changes at the mesophase-isotropic transition, which is supported by the gain of order observed by X-ray diffraction. The electrical properties were investigated by modeling the current-voltage characteristics by a space-charge-limited current transport with a field dependent mobility.

Item Type: Article
Erschienen: 2013
Creators: Eccher, Juliana and Faria, Gregório C. and Bock, Harald and von Seggern, Heinz and Bechtold, Ivan H.
Title: Order Induced Charge Carrier Mobility Enhancement in Columnar Liquid Crystal Diodes
Language: English
Abstract:

Discotic molecules comprising a rigid aromatic core and flexible side chains have been promisingly applied in OLEDs as self-organizing organic semiconductors. Due to their potentially high charge carrier mobility along the columns, device performance can be readily improved by proper alignment of columns throughout the bulk. In the present work, the charge mobility was increased by 5 orders of magnitude due to homeotropic columnar ordering induced by the boundary interfaces during thermal annealing in the mesophase. State-of-the-art diodes were fabricated using spin-coated films whose homeotropic alignment with formation of hexagonal germs was observed by polarizing optical microscopy. The photophysical properties showed drastic changes at the mesophase-isotropic transition, which is supported by the gain of order observed by X-ray diffraction. The electrical properties were investigated by modeling the current-voltage characteristics by a space-charge-limited current transport with a field dependent mobility.

Journal or Publication Title: ACS Applied Materials & Interfaces
Volume: 5
Number: 22
Publisher: American Chemical Society
Uncontrolled Keywords: organic electronics, charge carrier mobility, columnar liquid crystals, perylenediimide, homeotropic alignment, interface effect
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Electronic Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 15 May 2017 09:24
Official URL: http://doi.org/10.1021/am403681q
Identification Number: doi:10.1021/am403681q
Funders: The authors thank the following institutions for financial support: CAPES, CNPq, and INCT/INEO., G.C.F. acknowledges the fellowship by the "Fundacao de Amparo a Pesquisa do Estado de Sao Paulo" (FAPESP) (Proc-number 2008/01935-5 and 2012/01303-4) and by the "Deutscher Akademischer Austauschdienst" (DAAD) (A/09/72945; ref 415)., H.v.S. acknowledges the scholarship "Special Visiting Researcher" by the Brazilian Science without Borders Program (CNPq and Capes Proc-number 400133/2012-1).
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