Preparation of polythiophene thin films by UV laser-assisted deposition of 2,5-dichlorothiophene with a 248 nm excimer laser beam

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 116; no. 3; pp. 245 - 249
• Main Authors: Nishio, Satoru, Okada, Shin-ichi, Minamimoto, Yae, Okumura, Motoyoshi, Matsuzaki, Akiyoshi, Sato, Hiroyasu
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30.07.1998; Elsevier Science
• Subjects: Applied sciences; Exact sciences and technology; Physicochemistry of polymers; Polymerization; Polymers and radiations; Polythiophene thin films; UV laser-assisted deposition; UV laser-assisted deposition; Polythiophene thin films; Characterization; Five membered ring; Sulfur heterocycle; Near ultraviolet radiation; Photopolymerization; Morphology; Preparation; Thin film; Surface structure
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/S1010-6030(98)00311-6

Polythiophene thin films are prepared by UV laser-assisted deposition (UV-LAD) of 2,5-dichlorothiophene (2,5-DCT) with a 248 nm (KrF) beam at several fluence values. Surface morphologies of the films dependent strongly on laser fluence and deposition rate of the reactant. In the optimized conditions, mesh-like structures consisting of numerous fibers were observed. Electric conductivity of the film prepared by UV-LAD at 10 mJ cm −2 pulse −1 increased from less than 10 −7 S cm −1 up to 10 −3 S cm −1 on iodine doping. FT-IR, photoelectron spectroscopy (XPS) and ultra violet—visible (UV—vis) spectroscopy measurements show that, although sulfur atoms are eliminated to some extent, polymerization occurs basically at 2 and 5 positions of 2,5-DCT by effective elimination of halogen atoms to form polythiophene with various π-conjugation lengths. The film contained both soluble and insoluble components in tetrahydrofuran (THF) and acetonitrile (AN) solvents. Components with π-conjugation length corresponding to those of an oligothiophene with 3 ± 1 thiophene units are dominant for soluble components. Optical band gap is estimated to be 2.93 eV for insoluble components in the film.