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Proceedings Paper

Determination of carrier mobility of amorphous organic electronic material by thin film transistor configuration
Author(s): C. H. Cheung; K. K. Tsung; S. K. So
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Paper Abstract

We demonstrate that organic thin film transistors (OTFTs) can act as an alternative tool for carrier mobility evaluation in amorphous organic electronic materials. OTFT is a three terminal device which can be operated with an active layer of film thickness thinner than 100 nm. The materials under investigation are phenylamine-based (PA) compounds, which are amorphous hole transporting materials widely used in organic light emitting diodes (OLEDs). The field effect (FE) mobilities of PA compounds (hole) were determined in a TFT configuration. For the case of N,N'-diphenyl-N,N'-bis(1-naphthyl) (1,1'biphenyl)-4,4'diamine (NPB), the FE mobility was found to be 2 × 10-5 cm2/Vs. It is about one order of magnitude smaller than that obtained from independent time-of-flight (TOF) technique (2 x 10-4 cm2/Vs) using a thick film of ~ 5 μm. Temperature dependent measurement was performed under temperature ranging from 235 to 360 K. The extracted energetic disorder by means of the Gaussian Disorder Model from OTFT was 85meV, which was larger than that of TOF (~74 meV). Similar observations were found in other PA compounds. The increase in the extracted disorder parameter in TFT configuration was one of the origins of the discrepancy between the FE and TOF mobility. OTFTs can be regarded as a useful tool for carrier mobility evaluation with little material consumption.

Paper Details

Date Published: 2 September 2008
PDF: 9 pages
Proc. SPIE 7051, Organic Light Emitting Materials and Devices XII, 70511M (2 September 2008); doi: 10.1117/12.793650
Show Author Affiliations
C. H. Cheung, Hong Kong Baptist Univ. (Hong Kong China)
K. K. Tsung, Hong Kong Baptist Univ. (Hong Kong China)
S. K. So, Hong Kong Baptist Univ. (Hong Kong China)

Published in SPIE Proceedings Vol. 7051:
Organic Light Emitting Materials and Devices XII
Franky So; Chihaya Adachi, Editor(s)

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