Scalable Synthesis of Fused Thiophene-Diketopyrrolopyrrole Semiconducting Polymers Processed from Nonchlorinated Solvents into High Performance Thin Film Transistors

The synthesis and characterization of a fused thiophene-diketopyrrolopyrrole based semiconducting polymer PTDPPTFT4 is presented. A number of synthetic challenges have been overcome in the development of a practical scalable synthesis. Characterization by Gel Permeation Chromatography (GPC) over a range of temperatures has revealed the tendency of this polymer to aggregate even at elevated temperatures and confirmed that the molecular weight values obtained are for nonaggregated material. This polymer meets a number of important requirements for potential industrial applications, such as scalable synthesis, solubility in industrially suitable solvents, and material stability and processability into stable high performance thin film transistor devices. Computational modeling has been used to help explain the structure property relationships contributing to the high performance. Grazing incidence X-ray of the thin films showed out of plane lamellar packing and in plane pi-pi stacking, both good indicators of a preferentially oriented thin film, desirable for high charge carrier mobility. Hole mobilities in excess of 2 cm(2)/V.s, on/off ratio of >10(6), and threshold voltage <2 V have been achieved.