Keto defect sites in fluorene-based organic field-effect transistors: The origin of rapid degradation on the performance of the device
- Center for Frontier Materials, Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, 1 Oryong-Dong, Buk-Gu, Gwangju 500-712 (Korea, Republic of)
The effect of keto defects in fluorene units on the performance of organic field-effect transistors (OFETs) was examined based on fluorene end-capped fused bithiophenes (BFTT) and biphenyl end-capped fused bithiophene oligomers (BPTT). The formation of keto defects after various periods of UV illumination in air on BFTT films was confirmed by the increase of the long-wavelength emission at 2.1-2.3 eV in the photoluminescent (PL) spectrum and the generation of a Fourier transfer infrared (FTIR) peak at 1721 cm{sup -1}, corresponding to the carbonyl stretching mode of the fluorenone moiety. For both BPTT films irradiated in air and BFTT in nitrogen, i.e., a keto-free system, no increase in long-wavelength emission in the PL spectrum, was found and the peak corresponding to the carbonyl stretching mode of the fluorenone moiety was absent in the FTIR spectrum. The threshold voltage, i.e., switch-on voltage, of the OFETs was increased and the field-effect mobility and on-state drain current were rapidly decreased after the formation of ketonic defects, since these defects induce the formation of numerous trap sites in the band gap of the semiconducting conjugated oligomer. The density of trap sites (N{sub t}) generated after the formation of keto defects was determined using space-charge-limited current spectroscopy. A N{sub t} of around 2.7x10{sup 15} cm{sup -3} was found for the BFTT film due to the formation of keto defects after 6 h of UV irradiation.
- OSTI ID:
- 20709676
- Journal Information:
- Journal of Applied Physics, Vol. 97, Issue 10; Other Information: DOI: 10.1063/1.1897068; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
AIR
BIPHENYL
CARBONYLS
CARRIER MOBILITY
CRYSTAL DEFECTS
ELECTRIC POTENTIAL
EV RANGE 01-10
FIELD EFFECT TRANSISTORS
FLUORENE
FOURIER TRANSFORMATION
INFRARED SPECTRA
NITROGEN
ORGANIC SEMICONDUCTORS
PERFORMANCE
PHOTOLUMINESCENCE
SPACE CHARGE
SPECTROSCOPY
THIN FILMS
THIOPHENE
ULTRAVIOLET RADIATION