Synthesis Of Donor-Acceptor Type Polythiophene Derivatives Via Direct C-H/C-H Coupling Polycondensation And Their Photoelectric Properties

Polythiophene and its derivatives have been widely used in organic solar cells,organic light-emitting diodes,chemical/biological sensors and other fields.Donor(D)-acceptor(A)type(ie D-A type)polythiophene derivatives due to the unique push-pull electronic interaction on the polymer backbone,An efficient intramolecular charge transfer(ICT)can occur between the donor(D)and acceptor(A)units,By combining different D units and A units,ICT and molecular orbital energy levels can be effectively adjusted,realize the performance requirements of conjugated polymer materials in different applications.At present,D-A polythiophene derivatives are mainly synthesized by cross-coupling reactions catalyzed by transition metals(such as Suzuki,Stille and Kumada reactions).These classical synthesis methods require pre-functionalization of monomers,that is to prepare the corresponding aromatic halides and boric acid esters or aromatic organometallic compounds(such as tin reagents or Grignard reagents,etc.),then,polycondensation is carried out in the presence of metal catalysts such as Pd and Ni to prepare D-A conjugated polythiophene.The monomer pre-functionalization steps are complicated,the reaction conditions are harsh,the prepared organometallic reagent has poor stability,is difficult to purify,and has high cost.In response to these problems,this thesis used transition metal-catalyzed direct C-H/C-H coupling polycondensation to synthesize a series of D-A polythiophene derivatives,explored the polymerization mechanism,and systematically investigated the photovoltaic performance and OLED performance of the polymer.The specific research content is as follows:1.Synthesis and polymerization mechanism of carboxylate substituted polythiophenederivatives.Basedon(bis(2-butyloctyl)[2,2'-bithiophene]-4,4'-dicarboxylate)(A)and three donor units,namely 2,2'-Bithiophene,3,3''-Dioctyl-2,2':5',2''-tertthiophene and thiophene(D)are monomers,and 3 kinds of carboxylate substituted polythiophene derivatives are prepared by direct C-H/C-H coupling polycondensation method(P1-P3).The polymer structure and molecular weight were characterized by ¹H NMR and ¹³C NMR spectroscopy,infrared spectroscopy,and gel permeation chromatography(GPC),and the P1 was compared with the control polymer P1*synthesized by the Stille coupling method.The structure of the polymer was further determined.The effects of solvent type,reaction temperature and catalyst type on the polycondensation reaction were investigated,and the polymerization reaction conditions were optimized.On this basis,with(bis(2-butyloctyl)[2,2'-bithiophene]-4,4'-dicarboxylate)and3,3'-dioctyl-2,2'-Bithiophene polycondensation is a reaction model,and the influence of monomer reactivity ratio,reaction time and other factors on the polymerization reaction is explored,and a possible polymerization mechanism is proposed.2.Study on the photovoltaic performance of carboxylate substituted polythiophene derivatives.Using UV-Vis absorption spectroscopy,fluorescence spectroscopy,electrochemical workstation,XRD,TGA and other technical means,the optical and electrochemical properties,crystallinity and thermal stability of P1-P3were characterized,and combined with the DFT calculation results,the influence of different thiophene spacer lengths on polymer properties is discussed.Using P1-P3 as donor materials,photovoltaic devices were prepared,and their microscopic morphology and photovoltaic performance were investigated.Under optimized conditions,the photoelectric conversion efficiency(PCE)of photovoltaic devices based on P1-P3 are 5.18%,0.67%,and 0.17%,respectively.3.Synthesis of polythiophene derivatives containing fluorinated benzotriazole structural units and research on OLED performance.Using5,6-difluoro-2-(2-hexyldecyl)-2H-benzotriazole as monomer A,3-octylthiophene and2,2'-dithiophene as monomer D,Two kinds of polythiophene derivatives(P5 and P6)containing fluorinated benzotriazole structural units were prepared by direct C-H/C-H coupling polycondensation method.Using UV-Vis absorption spectroscopy,fluorescence spectroscopy,electrochemical workstation and TGA and other technical means to investigate their photophysical properties,electrochemical properties and thermal stability.The OLED devices with P5 and P6 as the light-emitting layer respectively showed green light(0.40,0.52)and red light(0.66,0.33),and the maximum brightness and current efficiency of the device are 774 cd/m² and 0.12 cd/A,1178 cd/m² and 0.25 cd/A,respectively.