The Effect Of The Position And Number Of Fluorine Atoms On The Properties Of The DA Conjugated Polymer

Human survival depends on the limited energy sources, such as oil, coal, However, with the excessive consumption, which caused scarcity and environmental pollution of the resources, which effects the health of human body. As the best alternatives, solar energy appeal to much attention from lots of researchers. Solar cells have developed for nearly half a century from the original silicon to the organic solar cells. Compared to commercial and practical inorganic battery of reactants, organic solar cells are lower cost, more easily to obtain materials, and could be used for the preparation of the flexible components, etc. To improve the power conversion efficiency, the key to achieve the goal is to enhance utilization of active material of light absorption layer. Designing the molecular structure of narrow band gap in favor of the electron delocalization and carrier transfer, which could enhance the short circuit current. To get better molecular planarity by designing similar eoplanar aromatic structure or through the introduction of atoms in the side chain, groups increase or decrease resistance of the backbone of the polymer chain structure to improve torsion Angle, which also can improve the intermolecular ?-? stacking, and finally increase short circuit current.This paper based on two kinds of molecular of star molecular polythiophene derivatives and dialkoxyl benzene with diazosulfide (BT), introducing the fluorine atoms onto acceptor units of molecular in order to improve planarity and enhance short circuit current. Through Stille cross-coupling reaction synthesized, here synthesized two kinds of new copolymer PTCBT, PTCFBT, PFTCBT and PFPTBT, PFPFTBT, PPFTBT respectively, and prepared heterojunction solar cells. Then explore the property of the polymer solar cells, the specific work as follows:(1) With the three polymers, bulk heteroj unction solar cells are prepared. The polymer and devices were characterized, and explore the photovoltaic performance, etc, the results show that:by thermogravimetric analysis determination,the three polymers exhibit good thermodynamic stability. Determined by ultraviolet absorption spectrophotometer, PTCFBT and PFTCBT two polymers which introduce fluorine atoms, the absorption edges at 700 nm and 760 nm respectively. The membrane of polymer PTCBT, PTCFBT, PFTCBT corresponding maximum absorption peak at 552 nm,516 nm, 586 nm. Through the determination of cyclic voltammetry, the LUMO energy levels of polymer PTCBT, PTCFBT, PFTCBT respectively 2.85 eV,2.94 eV and 2.87 eV. The HOMO energy level is 5.26 eV,5.64 eV and 5.49 eV. Photovoltaic performance measurement of devices based on three kinds of polymer materials for solar cells, the power conversion efficiency are 4.70%,4.99% and 5.93% respectively. Morphology of with PC71BM blend actives layers are good with the smaller roughness. XRD test showed that polymer PTCFBT, PFTCBT which introduce the fluorine atoms is conducive to molecular crystal accumulation.(2) Determined by ultraviolet absorption spectrophotometer, corresponding maximum absorption peak of solid state of polymer PFPFTBT, PFPTBT, PPFTBT at 595 nm,527 nm to 642 nm. The different position of fluorine make different influence on molecular band gap. Tested by cyclic voltammetry, LUMO energy levels of polymer PFPFTBT, PFPTBT, PPFTBT are respectively 3.0 eV,2.96 eV and 2.98 eV, HOMO energy level is 5.76 eV,5.75 eV and 5.31 eV. Fluorine atoms can decrease the molecular level, the more the number, lower level, and the fluorine atoms location may form covalent bonds of C and S atoms to change molecular planarity, finally increase the short circuit current. Photovoltaic performance measurement device based on three kinds of polymer materials for solar cells, the power conversion efficiency of 3.93%%,6.40%, 9.39%.