Keto defect sites in fluorene-based organic field-effect transistors: The origin of rapid degradation on the performance of the device
- 저자
- Yong-Young Noh , Dong-Yu Kim, Yuji Yoshida, Kiyoshi Yase, Byung-Jun Jung, Eunhee Lim, Hong-Ku Shim, and Reiko Azumi
- 저널명
- Journal of Applied Physics, 97, 104504 (2005)
- 년도
- 2005
- Link
- https://doi.org/10.1063/1.1897068 101회 연결
The effect of keto defects in ¯uorene units on the performance of organic ®eld-effect transistors sOFETsd was examined based on ¯uorene end-capped fused bithiophenes sBFTTd and biphenyl end-capped fused bithiophene oligomers sBPTTd. The formation of keto defects after various periods of UV illumination in air on BFTT ®lms was con®rmed by the increase of the long-wavelength emission at 2.1±2.3 eV in the photoluminescent sPLd spectrum and the generation of a Fourier transfer infrared sFTIRd peak at 1721 cm−1, corresponding to the carbonyl stretching mode of the ¯uorenone moiety. For both BPTT ®lms 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 ¯uorenone moiety was absent in the FTIR spectrum. The threshold voltage, i.e., switch-on voltage, of the OFETs was increased and the ®eld-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 sNtd generated after the formation of keto defects was determined using space-charge-limited current spectroscopy. A Nt of around 2.7 31015 cm−3 was found for the BFTT lm due to the formation of keto defects after 6 h of UV irradiation.