Control of the molecular orientation of a 2,2′-bithiophene-9,9-dioctylfluorene copolymer by laser annealing and subsequent enhancement of the field effect transistor characteristics

Kubota, Korefumi; Kato, Takuji; Adachi, Chihaya
August 2009
Applied Physics Letters;8/17/2009, Vol. 95 Issue 7, p073303
Academic Journal
We controlled the orientation of a 2,2′-bithiophene-9,9-dioctylfluorene (F8T2) copolymer spin-coated film on a polycarbonate substrate using a laser-annealing technique and demonstrated an enhancement of the field-effect transistor characteristics. We used a semiconductor laser, having a lasing wavelength of λ=405 nm, with a small spot size of 400 nm. Using polarizing optical microscopy and x-ray diffraction analysis, we confirmed enhancement of the orientation of the molecular chains of F8T2, along the laser scanning direction. Following laser annealing, the field-effect hole mobility resulted in a value of μ=1.6×10-3 cm2/V s, which is about three times higher than that of the unannealed sample.


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