Optoelectronic properties of polythiophene thin films and organic TFTs fabricated by oxidative chemical vapor deposition

Fabrication of devices utilizing unsubstituted polythiophene (PT) has received limited attention because thin films of this insoluble material have been difficult to prepare using traditional solution-based methods. However, since the thiophene monomer is volatile, PT films can be readily fabricated...

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Bibliographic Details
Published in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2014-09, Vol.2 (35), p.7223-7231
Main Authors: Borrelli, David C., Lee, Sunghwan, Gleason, Karen K.
Format: Article
Language:English
Subjects:
Absorption spectra
Chemical vapor deposition
Deposition
Optoelectronics
Polythiophene
Semiconductor devices
Thin film transistors
Thin films
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Summary:Fabrication of devices utilizing unsubstituted polythiophene (PT) has received limited attention because thin films of this insoluble material have been difficult to prepare using traditional solution-based methods. However, since the thiophene monomer is volatile, PT films can be readily fabricated by oxidative chemical vapor deposition (oCVD). The pressure of the oCVD process is here shown to significantly affect the optoelectronic properties of the PT films. Shifts in the Raman bands near 1500 cm super(-1) suggest that the lowest pressure deposition conditions (1 mTorr) result in shorter conjugation. Additionally, relative Raman peak intensities suggest that the polymer chains in these films contain more distortions than films deposited at higher pressures. UV-Vis absorption spectra of the oCVD PT films show that films deposited at the lowest pressure considered (1 mTorr) are slightly blue-shifted and demonstrate lower absorption than films deposited at higher pressures. PT films deposited at 75, 150, and 300 mTorr demonstrated similar UV-Vis absorption spectra, with absorption maxima near 515 nm. Organic thin film transistors (TFTs) were fabricated using oCVD PT as the active channel layer to analyze the effect of deposition pressure on charge transport and electrical properties. Films deposited at 150 mTorr demonstrate the greatest field effect carrier mobility of 4 10 super(-3) cm super(2) V super(-1) s super(-1).
ISSN:2050-7526
2050-7534
DOI:10.1039/C4TC00881B