Novel Conjugated Polymers:Synthesis And Optoelectronic Properties

Design and synthesis of conjugated polymers has been a hotspot in the research of the field of materials chemistry. They are widely utilized in the field of organic semiconductor field due to their flexible manufacturing and good optoelectronic properties. Major work of this dissertation is focused on the design and synthesis of a series of conjugated polymers materials, which have the unique optoelectronic properties and meet the requirements of different organic electronic devices, through studying the relationship between structure and property of conjugated polymer. Furthermore, the potential application of these polymers as active layer in polymer solar cells and polymer light emitting diodes is explored, according to the characteristics of polymers.In chapter2, a series of novelty acceptor unit [1,2,3]triazolo[4,5-g]quinoxaline (TzQx) were developed, which has branched alkyl chains at thiophene spacer or long alkoxy chains at triazoloquinoxaline acceptor unit. It is the first report discussing copolymers based on triazoloquinoxaline electron acceptor unit and benzo[1,2-6:4,5-b’]dithiophene (BDT) electron donor unit. The solubility, optical, electrochemical and photovoltaic properties of resulted polymers effected by alkyl or alkoxy chains were studied in detail. The introduction of side chains onto the thiophene spacer or quinoxaline unit lowered the highest occupied molecular orbital energy level of the polymers, while excessive chains prevent the polymer backbone from π-π stacking and result in a lowed photovoltaic performance. The best bulk heterojunction (BHJ) polymer solar cells (PSCs) device by blending PBDT-BTzQx-EH-C1(P2) with PC61BM exhibited a maximum power conversion efficiency (PCE) of2.24%, after optimized device by adding PFN/Ca cathode interfacial layers.In chapter3, we tried to enlarge conjugated framework of benzothiadiazole via fusing quinoxaline or phenazine, resulted units called thiadiazolo [3,4-g] quinoxaline (DTBTQx) and thiadiazolo[3,4-i]phenazine (DTBTBPz). Two new narrow band gap copolymers PBDT-DTBTQx and PBDT-DTBTBPz comprised of DTBTQx or DTBTBPz acceptor unit and BDT donor unit have been synthesized and application for polymer solar cells. The solubility, optical, electrochemical and photovoltaic properties of copolymers effected by different fused acceptor units were investigated. The PSCs devices PCE is not high, but these kinds of electron acceptor units with strong electron-withdrawing ability can be used to build the ultra-narrow band gap alternating copolymers. In chapter4, a new electron-donating unit, thiophenyl-methylene-9H-fluorene, was developed and used for the design of D-A polymers for PSCs application for the first time. By conjugated thiophene with fluorene unit through methylene, thiophenyl-methylene-9H-fluorene shows more planar conformation and stronger electron donating ability. By alternating thiophenyl-methylene-9H-fluorene with several acceptor units, the narrow bandgap copolymers were synthesized. The solubility, optical, electrochemical and photovoltaic properties of resulted polymers effected by different acceptor units were studied in detail. Among them, PFTTTz-THF (P4) based on thiophenyl-methylene-9H-fluorene donor unit and thiazolo[5,4-d]thiazole (THz) acceptor unit, showed best PCE of2.21%, after PSCs device added PFN/Ca cathode modified layers. At the same time, a series of novelty polymers based on thiophenyl-methylene-9H-fluorene,9,9-dialkyl-9H-fluorene,9-alkylidene-9H-fluorene, carbazole-substituted triphenylamine donor units and BTzQx acceptor unit were synthesized. The solubility, optical, electrochemical and photovoltaic properties of resulted polymers were discussed. Among them, the device based of PFDTBTzQ-2OC1(P1) alternated9,9-dialkyl-9H-fluorene donor and BTzQx acceptor unit, delivered a PCE of2.42%after device optimization. A series of new donor units, aniline with substituents imine-bridged fluorene, were synthesized. Three of them polymerized with BTzQx acceptor, resulted narrow band gap copolymers. The solubility, optical, electrochemical and photovoltaic properties of resulted polymers effected by introduction of different substituents (methyl, F atoms and trifluoro methoxy) on aniline imine-bridged fluorene were studied in detail.In chapter5, new polymers based on naphthodifuran (NDF) donor unit and fused conjugated benzotriazole or benzothiadiazole acceptor unit have been synthesized. The solubility, optical, and electrochemical properties of resulted polymers were studied in detail. The BHJ solar cell devices based on these polymers are undergoing.In chapter6,2-D fluorene-alt-bithiophene based polymers with phenylvinyl bridged accepting side chain have been developed by grafting different electron-withdrawing groups including malononitrile,1,3-indanedione,4-nitrophenyl acetonitrile onto polymer backbone. The influence of accepting side chain on the optical and electrochemical properties of resulted polymers was investigated and polymers were explored as the active layer in polymer light emitting diodes.