Synthesis and Properties of Phenothiazylene Vinylene-Based Polymers: New Organic Semiconductors for Field-Effect Transistors and Solar Cells

Abstract

A series of new phenothiazylene vinylene-based semiconducting polymers, poly[3,7-(4'-dodecyloxyphenyl)phenothiazylene vinylene] (P1), poly[3,7-(4'-dodecyloxyphenyl)phenothiazylene vinylene-a/t-1,4-phenylene vinylene] (P2), and poly[3,7-(4'-dodecyloxyphenyl)phenothiazylene vinylene-a/t-2,5-thienylene vinylenel (P3), have been synthesized via a Horner-Emmons reaction. FTIR and H-1 NMR spectroscopies confirmed that the configurations of the vinylene groups in the polymers were all-trans (E). The weight-averaged molecular weights (M-w) of P1, P2, and P3 were found to be 27,000, 22,000, and 29,000, with polydispersity indices of 1.91, 2.05, and 2.25, respectively. The thermograms for P1, P2, and P3 each contained only a broad glass transition, at 129, 167, and 155 degrees C, respectively, without the observation of melting features. UV-visible absorption spectra of the polymers showed two strong absorption bands in the ranges 315-370 nm and 450-500 nm, which arose from absorptions of the phenothiazine segments and the conjugated main chains. Solution-processed field-effect transistors fabricated from these polymers showed p-type organic thin-film transistor characteristics. The field-effect mobilities of P1, P2, and P3 were measured to be 1.0 x 10(-4), 3.6 x 10(-5), and 1.0 x 10(-3) cm(2) V-1 s(-1), respectively, and the on/off ratios were in the order of 10(2) for P1 and P2, and 10(3) for P3. Atomic force microscopy and X-ray diffraction analysis of thin films of the polymers show that they have amorphous structures. A photovoltaic device in which a P3/PC71BM (1/5) blend film was used as the active layer exhibited an open-circuit voltage (V-OC) of 0.42 V, a short circuit current (J(SC)) of 5.17 mA Cm-2, a fill factor of 0.35, and a power conversion efficiency of 0.76% under AM 1.5 G (100 MW cm(-2)) illumination. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48:635-646,2010