Direct Arylation Synthesis Of Conjugated Polymers And Their Applications In Optoelectronic Devices

Compared with inorganic semiconductor materials,organic semiconductor materials have attracted extensive attention and research due to their unique properties such as easy chemical structure regulation,flexibility and lightness,and high efficiency and low cost device fabrication through printing and other processing technologies.Among polymer-based semiconductor materials,the donor-acceptor type(D-A)conjugated polymers play a dominant role and show excellent device performance,such as organic photovoltaic materials and high carrier mobility materials.At present,these high-performance D-A conjugated polymers are mainly synthesized by traditional cross-coupling methods catalyzed by transition metals such as Stille or Suzuki coupling.In this paper,a series of D-A conjugated polymers were synthesized by direct arylation polymerization using benzodithiophene(BDT)and cyclopentadienodithiophene(CDT)based building blocks as donor units and benzothiadiazole(BT)based building blocks as acceptor units.Then these polymers were applied to organic solar cells(OSCs)and organic field effect transistors(OFETs),respectively,to explore the differences between direct arylation polymerization and the traditional polymerization,and develop an efficient,simple and green polymerization method suitable for conjugated polymers'preparation.Furthermore the influence of chemical molecular structure changes on the physical,chemical and photovoltaic properties of polymer materials was also investigated.The main research contents of this paper are listed below:In chapter one,conjugated polymer materials for organic solar cell and field-effect transistor applications are summarized based on literature reports.In the second chapter,BDT was used as donor unit,phenol alkoxy group with two fluorine atoms was introduced into the benzene ring to increase the solubility of the polymer and regulate the energy levels of the polymer,and then polymerized with the acceptor unit BT to obtain PBDT-BT series of D-A conjugated polymers.We used the traditional Suzuki polymerization method and the new direct arylation polymerization method respectively,and successfully obtained a suitable direct arylation polymerization system for BDT.The PBDT-UPF-BT polymer and PBDT-Side F-BT polymer were synthesized respectively.The results show that PBDT-UPF-BT has better molecular symmetry and narrower band gap,which is beneficial to carrier transport and the device performance.In the third chapter,PCDT-BT series of conjugated polymers were prepared based on CDT as the donor unit and BT as the acceptor unit,which were also used traditional Suzuki,polymerization method and the direct arylation polymerization method.We successfully explored a suitable direct arylation polymerization system for CDT based polymers,and provided new aspect for organic semiconductor material industrialization production.Meanwhile,the influence of alkyl side chain length in donor unit on polymer properties was also studied.Two polymers PCDT-EH-BT polymer and PCDT-C16-BT were synthesized respectively.The hole mobilities of the two polymers were 0.007 cm~2V^-1s^-1,0.04 cm~2V^-1s^-1,respectively.The results shows that the introduction of straight long chain not only improved the solubility of polymer,but also reduced the band gap and improved the carrier mobility.