Ink-jet printed p-type polymer electronics based on liquid-crystalline polymer semiconductors

Abstract

Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophenes) (pBTTTs) - currently one of the most promising class of polymer semiconductors - are known to have a low-room-temperature solubility in a broad range of common organic solvents. By judicious selection of a suitable solvent for these rigid-rod-like, liquid-crystalline materials, we ink-jet printed poly(2,5-bis(3- dodecylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT-C12) into discrete thin-film field-effect transistors (FETs) that display on/off ratios of up to 107 and charge-carrier mobilities in the range of 0.05-0.1 cm2 V-1 s-1. Compared to spin-coated devices, the ink-jet printed devices typically had lower current leakage; indeed, gate-leakage currents were 1 to 2 orders of magnitude lower in ink-jet printed transistors. These overall device performance of ink-jet printed pBTTT-C 12 would be sufficient for, for instance, driving simple electrophoretic displays [T. N. Ng, S. Sambandan, R. Lujan, A. C. Arias, C. R. Newman, H. Yan and A. Facchetti, Appl. Phys. Lett., 2009, 94, 233307; G. H. Gelinck, T. C. T. Geuns and D. M. de Leeuw, Appl. Phys. Lett., 2000, 77, 1487-1489; H. E. A. Huitema, G. H. Gelinck, J. van der Putten, K. E. Kuijk, C. M. Hart, E. Cantatore, P. T. Herwig, A. van Breemen and D. M. de Leeuw, Nature, 2001, 414, 599-599; H. E. A. Huitema, G. H. Gelinck, J. van der Putten, K. E. Kuijk, K. M. Hart, E. Cantatore and D. M. de Leeuw, Adv. Mater., 2002, 14, 1201-1204.]. We demonstrate here integration of such ink-jet printed pBTTT-C12 transistors into unipolar digital logic gates, which produced a signal gain of more than 16. This is one of the highest gains reported for a unipolar-based logic gate and demonstrates the potential of pBTTT polymers for high performance application employing simple ink-jet printing procedures conducted in light and ambient air without any special precautions. © 2010 The Royal Society of Chemistry.