| Recently, the organic small molecular materials with quasi-three-dimensional structure have been extensively researched in the organic light emitting diode, organic photovoltaic and organic white light illumination. The structure with two conjugated chains connected by one single bond was one of the typical representatives of quasi-three-dimensional structure, which could increase the solubility of materials without introducing the excessive alkyl chains and inhibit materials crystallinity, conducive to form amorphous structure. In virtue of its binding method, the molecules were flexible and could adjust its spatial structure according to the environment, assuring to form dense and orderly films in preparing organic semiconductor devices. The quasi-three-dimensional structure was isotropic in the optical and electronic properties, which was benefit to enhance the carrier mobility. Owing to the unique properties of quasi-three-dimensional structure, a series molecules with low band gap using the5,5’-bizenzo[c][1,2,5]thiadiazole and3,3’-bithiophene as the central nodes have been designed and synthesized, and their application in organic solar cells as electron donor was also prospected. The thesis is mainly consisted and listed as follows:(1) Two materials with electron donor-acceptor type were synthesized by Stille coupling, in which5,5’-bizenzo[c][1,2,5]thiadiazole were used as central nodes, and fluorine and carbazole units as four arms. The dihedrals between the two benzothiazoles of the central nodes were approximately60°by molecular simulation, which indicated that these molecules were quasi-three-dimensional structure. These materials were used as electron donor materials and blended with the PC71BM as electron acceptor to prepare the organic solar cells by solution processing. The molecule with fluorine as electron donor showed a relatively low performance:power conversion efficiency (PCE)=0.74%with short circuit current (Jsc)=2.47mA/cm2, open circuit voltage (Voc)=1.09V and fill fact (FF)=27%.(2) Low PCE of meterials in chapter one may be caused by relatively bad film-forming ability with small molecular weight. In order to obtain higher PCE, materials with higher molecular weight were designed to enhance the film-forming ability and absorption ability. Two quasi-three dimensional structure molecules with5,5’-bizenzo[c][1,2,5]thiadiazole as central nodes, SFTBT(with molecular weight of4896g/mol) and SCzTBT(with molecular weight of5021g/mol), and their corresponding one dimension linear molecules (LFTBT and LCzTBT) were synthesized respectively. The dihedrals between the two benzothiazoles in the central node of the SFTBTB and SCzTBT molecules were approximately70°by molecular simulation, indicating that two molecules were quasi-three-dimensional structure. The molecule of LFTBT with one dimension linear structure was used as electron donor and blended with the PCBM as electron acceptor to prepare the bulk heterojucontion solar cells, which showed the PCE=2.84%with Voc=0.94V, Jsc=2.95mA/cm2and FF=58.3%, Correspondingly, the properties of SFTBT with quasi-three-dimensional structure was PCE=3.38%, Voc=1.08V, Jsc=6.75mA/cm2and FF=43%,19%higher compared with LFTBT. Also, the PCE of SCzTBT was higher than LCzTBT.(3) Using3,3’-bithiophene as the central nodes and4-cyanophenyl isocyanate as draw electron units at the end of the molecules, four low band gap oligothiophene molecules with quasi-three-dimensional structure were designed and synthesized. The dihedrals between the bithiophenes nodes were over80°by molecular simulation, which indicated that these molecules were quasi-three-dimensional structure. The length of the conjugated chain was extended by increasing the number of thiophene units, to explore the effect of it on the optical, electrical and thermodynamics properties. When using the DHPT-SC as electron donor and blending with PC71BM as electron acceptor to prepare the bulk heterojunciton solar cells, the PCE was1.70%with Voc=0.92V, Jsc=5.35mA/cm2, FF=34%.(4) Using3,3’-bithiophene as the central nodes, benzothiazole as draw electron units, three low band gap molecules with different alky chain were designed and synthesized. The dihedrals between the bithiophenes nodes were close to90°by molecular simulation, which indicated that these molecules were quasi-three-dimensional structure. The solubility and film-forming ability of the meterials were enhanced by fixed into substituents with different length alky chains, and their effect on the optical, electronics and thermodynamics properties were also investigated.(5) Three biaryl compounds of2T-CN,4T-CN and6T-CN were synthesized by using PdCl2dppf as catalyst without4,4,4’,4’,5,5,5’,5’-octamethyl-2,2’-bi-(1,3,2-dioxaborolane), the conditions of the reaction were also be optimization, such as the solvent, base and ligand.6T-CN showed a relatively well photovoltaic properties with PCE=2.03%, Voc=0.86V, Jsc=6.24mA/cm2, FF=38%。... |
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