Poly(2,7-carbazole) Derivatives as Semiconductors for Organic Thin-Film Transistors a Salem Wakim, Nicolas Blouin, Emilie Gingras, Ye Tao, Mario Leclerc * Introduction Organic semiconductors have recently received great attention because of their potential of applications as active layers in various electronic devices such organic light-emitting diodes (OLEDs), [1] organic field-effect tran- sistors (OFETs) [2] and photovoltaic cells (PCs). [3] Polymeric semiconductors are especially desirable due to their solution processability and good mechanical properties allowing their utilization in low-cost fabrication tech- niques (inkjet printing, roll-to-roll, etc.) and making them compatible with flexible plastic substrates. In the parti- cular case of p-type OFETs, regioregular poly(3-hexyl- thiophene) [4] (P3HT) and poly[(9,9 0 -n-dioctylfluorene)-alt- bithiophene] [5] (F8T2) have been extensively studied over the last 10 years. They exhibit mobility of about 0.1 and 0.02 cm 2  V 1 s 1 , respectively. However, the sensitivity of regioregular P3HT to atmospheric oxygen makes its OFET performances problematic in air. [6] In the case of the relatively stable F8T2, alignment of the polymer chains on rubbed polyimide substrate and annealing at high temperature in the liquid-crystalline phase are necessary to obtain high mobility. Recently, other polythiophene [7,8] and polyfluorene [9] derivatives with high mobility were also reported. The analyses of these polymeric FETs show Communication New poly(2,7-carbazole) derivatives have been synthesized using Yamamoto or Stille coupling reaction. These polymers are highly soluble in common organic solvents and have relatively high molecular weights. Solution-processed organic field-effect transistors using these new polymeric semiconductors were found to exhibit a hole mobility up to 2.0  10 3 cm 2 V 1 s 1 with a current on/off ratio of 5  10 4 under ambient conditions. S. Wakim, N. Blouin, E. Gingras, M. Leclerc Canada Research Chair on Electroactive and Photoactive Poly- mers, De ´partement de Chimie, Universite ´ Laval, Quebec City, Quebec, Canada G1K 7P4 Fax: (þ1) 418 656 7916; E-mail: mario.leclerc@chm.ulaval.ca S. Wakim, Y. Tao Institute of Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6 a : Supporting information for this article is available at the bottom of the article’s abstract page, which can be accessed from the journal’s homepage at http://www.mrc-journal.de, or from the author. 1798 Macromol. Rapid Commun. 2007, 28, 1798–1803 ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.200700307