Study On Synthesis And OFETs Properties Of D-A Type Derivates Based On DPP

Diketopyrrolopyrrole(DPP) is an excellent building block for high performance OFETs(Organic field-effect transistors), especially the DPP(Th)2 based materials attract much attention. In this paper, we choosed the DPP(Th)2 linked with benzaldehyde as key intermediate and synthetized two kinds of novel D-A type DPP-based derivatives. We hope that the introduction of vinyl component and benzene ring could extend the conjugation length without distorting the backbone structure; thus, such structures could yield efficient intermolecular π-π interactions. Branched alkyl chains were introduced into the nitrogen centers of the DPP(Th)2 monomer to increase solubility and processability from solution. Thermal stability, photophysical and electrochemical properties and OFETs performance of this two types of oganic semiconductors were also studied. Both as-prepared and annealed film microstructures were also assessed by atomic force microscopy (AFM) and X-ray diffractions (XRD) studies.The following are the two aspects of this work in this paper:1. We synthetized the new semiconductor TM1 by inclusion of dicyanovinyl. Its HOMO and LUMO energy levels and band gap were worked out to be -5.36 eV,-3.81 eV and 1.55 eV respectively. This material exhibited ambipolar response with balanced hole and electron mobilities, up to 0.1680 cm2V-1 s-1 and 0.0154 cm2V-1 s-1 annealing at 120℃. Surprisingly the constructed OFETs with good air stability were achieved. In XRD study, according to the first-order reflection, the d spacing of lamellar packing structure is 22.1 A. In AFM study, the films that were annealed at 90℃ exhibits interconnected granular domains with more smooth surfaces. However, both the XRD patterns and AFM images of thin films are almost unaltered after annealing at 120℃. Taking consideration of the compatibility of the alkyl chains of TM1 with OTS, molecules are more inclined to exhibit an edge-on packing conformation on the substrate along the alkyl directions within the thin film.2. We synthetized the new semiconductors TM2-TM4 by inclusion of dithiafulvenyl linked with different substituents. Their HOMO and LUMO energy levels and band gaps were worked out, of which the TM3 had the lowest(HOMO=-4.99 eV; LUMO=-3.77 eV; EgCV=1.22 eV) and the TM4 had the highest(HOMO=-4.92 eV; LUMO=-3.63 eV; EgCV=1.29 eV). These materials exhibited p-only response in air measurement and achieved the best performance annealing at 100℃. Also the TM3 had the highest hole mobility(7.9×10-4 cm2V-1s-1) and the the TM4 had the lowest(9.3×10-5 cm2V-1 s-1). Finally both as-prepared and annealed film microstructures were also examined by atomic force microscopy (AFM) and X-ray diffractions (XRD) studies. The TM3 showed more dense lamellar packing and smoother films annealing at 100℃.