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Probing Bulk Transport, Interfacial Disorders, and Molecular Orientations of Amorphous Semiconductors in a Thin‐Film Transistor Configuration
Author(s) -
Sit WaiYu,
Cheung Sin Hang,
Chan Cyrus Yiu Him,
Tsung Ka Kin,
Tsang Sai Wing,
So Shu Kong
Publication year - 2016
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201500273
Subject(s) - materials science , thin film transistor , amorphous solid , semiconductor , organic semiconductor , electron mobility , optoelectronics , transistor , oled , layer (electronics) , nanotechnology , crystallography , chemistry , physics , quantum mechanics , voltage
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 SiO 2 and polystyrene (PS). On SiO 2 , 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 SiO 2 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 SiO 2 is related to the orientations of the more planar molecules which tend to lie horizontally on the surface.