Photolithographic Fabrication of P3HT Based Organic Thin-Film Transistors with High Mobility

An original design and photolithographic fabrication process for Poly (3-hexylthiophene-2, 5-diyl) (P3HT) based Organic thin-film transistors (OTFTs) is presented. The structure of the transistors was based on the bottom gate bottom contact OTFT. The fabrication process was efficient, cost-effective, and relatively straightforward to implement. Most of the fabrication steps were performed at room temperature and atmospheric pressure, with the only exceptions being the high temperatures used for annealing the films and the low pressures used for depositing the metal contacts. More than 226 transistors were fabricated on a single wafer. The electrical characteristics and the geometry of the transistors were consistent across the wafer. Current-voltage (I-V) and atomic force microscopy (AFM) measurements were performed to characterize the primary electronic properties of the transistors and morphology of the P3HT, respectively. Two key performance parameters were extracted from these measurements, the threshold voltage and the field-effect mobility of the transistors. The measured mobility of these transistors was significantly higher than most results reported in the literature for other similar bottom gate bottom contact P3HT OTFTs. The higher mobility is explained primarily by the effectiveness of the fabrication process in keeping the interfacial layers free from contamination, as well as the annealing of the P3HT.