Synthesis And Photoelectronic Properties Of Dibenzothiophene-S,S-dioxide Based Conjugated Polymers

Conjugated photoelectronic polymers have the advantages of light weight, high stability,structural diversification, high photoelectric response, solution processable and easy tofabricate flexible devices, and have great potential application in polymer light-emitting diodie,polymer solar cell and organic field effect transistor, and are becoming the focus of currentresearch and development of new materials.Dibenzothiophene-S,S-dioxide (SO) is an electron-deficient moiety with rigid and planarstructure. All the atoms are at the highest valence, giving the SO moiety having a greatantioxidant capacity, high chemical and environmental stability. Moreover, SO moiety has alow-lying lowest unoccupied molecular orbital (LUMO) energy level, high fluorescencequantum yields and electron mobility. In this thesis, aiming at the lacks of the photoelectricfunctional polymers, we brought the advantages of SO moiety into the relative polymers, toexploit the new functions of SO moiety and improve the performance of the polymers, as wellas reveal a way to better the design and synthesis highly efficient and stable photoelectricfunctional polymers.1) SO moiety was incorporated into the white-emitting single polymer based on2,7-carbazole as the backbone and benzothiadiazole as the yellow emitting center, andeffectively improved the fluorescence quantum yields and charge-balance factor, alsonarrowed down the LUMO energy gaps between the blue and yellow chromophores, leadingto high efficient and stable white-light emission based on the relative device. The electronicluminous (EL) spectra of the device showed excellent stable in a large applied current densityrange of12-300mA/cm2. The device based on the white-emitting single polymer containingSO moiety exhibited the maximum power efficiency (PEmax) of8.0lm/W and maximumexternal quantum efficiency (EQEmax) of3.9%with the single layer device of structureITO/PEDOT:PSS/polymer/CsF/Al. The effecienies were4times of the device based on thepolymer without SO moiety.2) new D-A type thiophene-2,8-dioctyl-dibenzothiophene-S,S-dioxide (DTSO) moietyhad been designed and synthesized. DTSO unit was further incorporated into the poly(2,7-fluorene) with varying content, and high exciton utilization rate of34%,51%and56%for the related blue, green and white emitting polymers were obtained, respectively. And thedevice based on the related polymers showed the maximum luminous efficiency (LEmax) of3.4,8.8and7.5cd/A, and the maximum external quantum efficiency of5.3%was obtained basedon the white-emitting single polymer.3) SO moiety as the side chain was grafted into poly(2,7-fluorene), and more β phase wassuccessfully induced, leading to more rigid polymer chain and higher fluorescence quantumyields. The related polymer PFO-FSO1based single layer device showed the EQEmaxof2.1%,which was3times of that of polyfluorene without SO. The CIE coordinate of the PFO-FSO1is (0.16,0.08), which is the NTSC standard blue-emitting CIE coordinates. Moreover, the ELspectra of the device showed excellent stable in a large applied current density range of6-240mA/cm2. And it also found that electron-deficient side chain could induce more β phase ofpoly(2,7-fluorene) than electron-rich side chain. SO moiety as the side chain was grafted intothe water/alcohol soluble poly(2,7-fluorene) containing amino-group, which was used as thecathode materials of interfacial modification for polymer solar cells (PSCs). The PSC based onPCDTBT:PC71BM (1:4, w/w) as the active layer and the interfacial polymer with SO moiety,exhibited excellent performance with the power conversion efficiency (PCE) of6.46%, whichimproved about35%of PCE of the PSC without the interfacial polymer. The interfacialpolymer with aromatic groups in the side chain showed similar interfacial modificationproperty comparing to that without. In contrast, the electron-deficient SO moiety containerexhibited a little bit better interfacial modification performance.4) SO derivatives were copolymerized with strong electron-rich indacenodithiophene (IDT)moiety to build the medium band gap (~2.2eV) donor-acceptor copolymers, which were usedas the electron-donor for the polymer solar cells. The best PCE of the related device can reach3.81%, which is among the highest efficiencies in the polymers with the bandgap over2.2eV.SO moiety was incorporated into the narrow bandgap copolymers, and the related polymersolar cells exhibited a high PCE of4.93%, which is improved by about1%of PCE comparedwith the device based on the polymer without SO.