Synthesis And Properties Of Conjugated Polymers Based On Thiophene-flanked Isoindigo Derivatives

Organic thin film transistors have wide application prospect in the field of organic electronics due to light weight, good mechanical flexibility, easy processibility,flexible and diverse molecular design. In recent years,thanks to the scientists’constant efforts in expansion and optimizing for the strctures of polymer and OTFT device fabrication process, OFETs based on organic conjugated polymers have achieved a breakthrough progress with high mobility over 14 cm2V-1s-1 .Isoindigo is one of well- known acceptor units which were investigated most. In this paper, we designed and synthesized a series of conjugated polymers based on thiophene-flanked isoindigo and its derivatives, and their field effect performance and some other related properties were studied. The main research is as follows:(1) In chapter 2, two new conjugated polymers, PBTPBF-TT and PBTPBF-HH based on BTPBF and vinyl thiophene units with different side-chain positions were synthesized. Both the polymers showed a broad absorption spectra (covering 400-1600 nm) and remarkably low bandgaps (ca. 0.8 eV). Both the two polymers exhibited ambipolar transport, whereas PBTPBF-TT showed a much higher transport performance than PBTPBF-HH when evaluated. The best hole and electron mobilities were 0.86 cm2V-1s-1 and 0.13 cm2V-1s-1 for PBTPBF-TT ,and were 0.45 cm2V-1s-1 and 0.047 cm2V-1s-1 for PBTPBF-HH, respectively. The surface morphology and crystal properties of the two polymers were studied through GIXD and AFM, and the film for PBTPBF-TT showed better crystallinity and more regular surface morphology than that for PBTPBF-HH which explained PBTPBF-TT had a better performance. Overall,this study showed that a minimal change in their side-chain positions dramatically optimized the polymer’s charge transport performance.(2) In chapter 3, we designed and synthesized a novel acceptor building block,namely BTPPI, which allows for substitution at four nitrogen atoms, so that the polymer, PBTPPI-TT based on BTPPI shows good solubility with short substituents.The OTFT device based on PBTPPI-TT showed high ambipolar charge transport performance with hole and electron mobilities up to 2.69×10-2cm2V-1 and 2.21×10-2 cm2V-1s-1.