| Organic field effect transistors?OFETs? have promising applications in the organic electronics due to their unique advantages of low-cost, light-weight, flexible,solution-processible and large-area device electronics. The semiconducting energy level and molecular arrangements in solid state determine thermodynamic/chemical stabilities and change carrier mobility of the corresponding OFET devices. Accordingly, the design and synthesis of organic semiconductors with a suitable energy level is of great importance. In this work, we focuse on the design and synthesis of novel organic semiconductors and investigate the OFETs performance of the prepared organic semiconductors. The main contents are outlined as follows:?1? A series of new Acceptor-donor-acceptor type compounds entailing W1-W3 are designed and synthesized. These compounds had the same donor moiety of2,6-di?thiophen-2-yl?dithieno[3,2-b:2 ',3 '-d]thiophene and different acceptor groups of2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran?TCF?, dicyanovinyl?DCV?and 3-ethyl-2-thioxothiazolidin-4-one. Then the UV-visible absorption spectroscopy,electrochemistry and OFET device performance of the synthesized acceptor-donor-acceptor type compounds were thoroughly investigated. The results show that all compounds have high thermal stability and strong absorption in the visible light region. Among them,compound W1 with TCF as acceptor group display the lowest LUMO energy level of-3.74 eV and the smallest HOMO-LUMO band gap of 1.74 eV, suggesting the promising applications of TCF unit in low band gap organic semiconductors. W3 compounds show the highest device performance, and after annealing its mobility reaches 4.0 × 10-2 cm2/Vs.?2? Two compounds W4-W5 based on benzodithiophene quinoid are designed and synthesized. The UV-visible absorption spectroscopy, electrochemistry and OFET device performance of the synthesized compounds are thoroughly investigated. The results show all compounds have high thermal stability and strong absorption in the visible light region.Among them, this compounds display the very low LUMO energy level?<-4.5eV? and thesmallest HOMO-LUMO band gap?1.2eV?, certifing that the two molecules are typically low band gap materials. In addition, the study finds that the quinone structure toward different direction could lead to a different molecular packing mode. W4 indicates the H-type aggregation are dominated in the thin films, but W5 exhibited the J-type aggregation.W4-W5 show the typical electron transport properties of n-type, and corresponding electron mobility of 1.32×10-5cm2/Vs and 9.30×10-4cm2/Vs, respectively.?3? Series of dithieno[3,4-c]-pyrrole-4,6-dione?di-TPD? involving polymers?W6-W10?are synthesized. The UV-visible absorption spectroscopy, electrochemistry and OFET device performance of the synthesized compounds are thoroughly investigated, which have potential to be act as ambipolar semiconductors. Due to the more electron deficiency of di-TPD building unit, the LUMO energy level for W6-W10?<- 3.4 eV? were lower than that of TPD.The results showed that the introduction of different polymerization monomers can fine-tune the energy level of the polymer. The OFET testings demonstrate, that compound W6, shows the typical transport property of p-type, and after annealing, its mobility reaches 0.16 cm2/Vs.Compounds, W7 and W8, shows the typical transport property of ambipolar semiconductors,and after annealing,their hole-dominated charge mobilities are 0.13 cm2V-1s-1and 4.23 ×10-2cm2V-1s-1 and 9.30×10-4 cm2/Vs respectively. By the way, because of the device of low-lying structure, their electron mobilities are rather low. W9 and W10 transistor performance are being further investigated. |
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