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Proceedings Paper

Directional solidification of C8-BTBT films induced by temperature gradients and its application for transistors
Author(s): Ichiro Fujieda; Naoki Iizuka; Yosuke Onishi
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Paper Abstract

Because charge transport in a single crystal is anisotropic in nature, directional growth of single crystals would enhance device performance and reduce its variation among devices. For an organic thin film, a method based on a temperature gradient would offer advantages in throughput and cleanliness. In experiments, a temperature gradient was established in a spin-coated film of 2,7-dioctyl [1]benzothieno[3,2-b]benzothiophene (C8-BTBT) by two methods. First, a sample was placed on a metal plate bridging two heat stages. When one of the heat stages was cooled, the material started to solidify from the colder region. The melt-solid interface proceeded along the temperature gradient. Cracks were formed perpendicular to the solidification direction. Second, a line-shaped region on the film was continuously exposed to the light from a halogen lamp. After the heat stage was cooled, cracks similar to the first experiment were observed, indicating that the melt-solid interface moved laterally. We fabricated top-contact, bottom-gate transistors with these films. Despite the cracks, field-effect mobility of the transistors fabricated with these films was close to 6 cm2 /Vs and 4 cm2 /Vs in the first and second experiment, respectively. Elimination of cracks would improve charge transport and reduce performance variation among devices. It should be noted that the intense light from the halogen lamp did not damage the C8-BTBT films. The vast knowledge on laser annealing is now available for directional growth of this type of materials. The associated cost would be much smaller because an organic thin film melts at a low temperature.

Paper Details

Date Published: 16 March 2015
PDF: 10 pages
Proc. SPIE 9360, Organic Photonic Materials and Devices XVII, 936012 (16 March 2015); doi: 10.1117/12.2078594
Show Author Affiliations
Ichiro Fujieda, Ritsumeikan Univ. (Japan)
Naoki Iizuka, Ritsumeikan Univ. (Japan)
Yosuke Onishi, Ritsumeikan Univ. (Japan)

Published in SPIE Proceedings Vol. 9360:
Organic Photonic Materials and Devices XVII
Christopher E. Tabor; François Kajzar; Toshikuni Kaino; Yasuhiro Koike, Editor(s)

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