Efficient High Area OFETs by Solution Based Processing of a π-Electron Rich Donor

• Published in: Chemistry of materials Vol. 18; no. 20; pp. 4724 - 4729
• Main Authors: Miskiewicz, Pawel, Mas-Torrent, Marta, Jung, Jaroslaw, Kotarba, Sylwia, Glowacki, Ireneusz, Gomar-Nadal, Elba, Amabilino, David B, Veciana, Jaume, Krause, Bärbel, Carbone, Dina, Rovira, Concepció, Ulanski, Jacek
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03.10.2006
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm060675m

We report on the preparation of high performance field-effect transistors (FETs) based on large areas of aligned films of a TTF derivative, namely, tetrakis-(octadecylthio)-tetrathiafulvalene (TTF-4SC18). TTF-4SC18 assembles into one-dimensional stacks in which the long alkyl chains promote intermolecular π−π overlapping due to their extremely closely packed nature. The films were prepared from solution by zone-casting, a simple technique that does not require the use of preoriented substrates. The films were characterized by AFM and X-ray, indicating an extremely high crystalline quality. The TTF molecules are tilted with respect to the substrate surface and are well-aligned in the casting direction. More than 40 FETs were measured, showing a remarkable reproducibility of their performance. The average charge carrier mobility value measured along the casting direction was about 0.006 cm2/V s for a channel length L = 100 μm and about 0.01 cm2/V s for L = 80 μm and L = 50 μm. The FET mobilities determined in the direction perpendicular to the orientation were ca. 1 order of magnitude lower. We found that all the devices after annealing exhibited an enhanced performance with FETs mobilities about 1 order of magnitude higher. The best devices revealed a charge carrier mobility close to 0.1 cm2/V s with an on/off ratio of the order of 104.