Document Type

Journal Article

Department/Unit

Department of Physics; Institute of Advanced Material

Abstract

Thin film transistors (TFTs) can be used to determine the bulk-like mobilities of amorphous semiconductors. Different amine-based organic hole transporting materials (HTs) used in organic light-emitting diodes have been investigated. In addition, the present study also measures the TFT hole mobilities of two iridium phosphors: Ir(ppy)3 and Ir(piq)3. These materials are grown separately on SiO2 and polystyrene (PS). On SiO2, the TFT mobilities are found to be 1–2 orders smaller than the bulk values obtained by time-of-flight (TOF) technique. On PS gate dielectric layer, the TFT mobilities are in good agreement TOF data. Only 10 nm of organic semiconductor is sufficient for TFTs to achieve TOF mobilities. Using the Gaussian disorder model, it is found that on SiO2 surface, when compared to the bulk values, the energetic disorders (s) of the HTs increase and simultaneously, the high temperature limits (µ∞) of the carrier mobilities decrease. Both s and µ∞ contribute to the reduction of the carrier mobility. The increase in s is related to the presence of randomly oriented polar Si-O bonds. The reduction of µ∞ on SiO2 is related to the orientations of the more planar molecules which tend to lie horizontally on the surface.

Publication Year

2016

Journal Title

Advanced Electronic Materials

Volume number

2

Issue number

3

Publisher

Wiley

First Page (page number)

1500273

Referreed

1

Funder

The support for this work under the Research Grant Council of Hong Kong under Grant No.#12201914 and #FRG2/12-13/080 is gratefully acknowledged. This work is also partially supported by the Research Grant Council of Hong Kong under Project #21201514.

DOI

10.1002/aelm.201500273

Link to Publisher’s Edition

http://dx.doi.org/10.1002/aelm.201500273

Copyright

This is the peer reviewed version of the following article: Sit, Wai-Yu, Sin Hang Cheung, Cyrus Yiu Him Chan, Ka Kin Tsung, Sai Wing Tsang, and Shu Kong So. "Probing bulk transport, interfacial disorders, and molecular orientations of amorphous semiconductors in a thin-film transistor configuration." Advanced Electronic Materials 2.3 (2016): 1500273, which has been published in final form at http://dx.doi.org/10.1002/aelm.201500273. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Keywords

charge transport, molecular orientation, organic light emitting diodes, organic thin-film transistors, time of flight

ISSN (electronic)

2199160X

Included in

Physics Commons

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