Study On The Synthesis And Photovoltaic Properties Of D-A Copolymers Containing Fluorinated Quinoxaline Unit

The organic photovoltaic cells （OPV） have many advantages of light weight, lowcost and so on. The polymers with excellent photovoltaic properties are vital to thedevelopment of OPV, it has become the hotspot and focus of study.In detail, the paper is devided into six chapters.In chapter1, the basic principle of photovoltaic cells and the development of thetypical conjugated polymers are introduced briefly. Then, the research situation ofquinoxaline materials and the influence of fluorine atom to the properties of materialshave been discussed in detail. Finally, the design ideas and the main studies of thispaper are put forward thereupon.In chapter2, PBDTQx and PBDTFQx are obtained by stille coupling reaction usingquinoxaline or fluorinated quinoxaline as acceptor and benzo[1,2-b:3,4-b′]dithiophene（BDT） as donor. The results shows that two polymers have rational absorption andgood thermal stability, Electrochemical cyclic voltammetry results show that thePBDTFQx has lower highest occupied molecular orbit （HOMO） and unoccupiedmolecular orbit （LUMO） energy level compared with the PBDTQx. The device basedon PBDTFQx has a higher power conversion efficiency （PCE） than PBDTQx-deviceunder the same conditions.In chapter3, PBDTTQx, PBDTFTQx; PBDTC6TQx, PBDTC6FTQx andPC₁₂BDTTQx, PC₁₂BDTFTQx are obtained using quinoxaline or fluorinatedquinoxaline derivatives as acceptor and BDT as donor. The results demonstrate thatthe polymers have broad absorption in long wavelength after the modification ofmolecular structure; the fluorinated polymers have lower HOMO energy levelcompared with the polymers without fluorine atom, which is favorable foropen-circuit voltage （Voc）. In addition, the SCLC indicates that PC₁₂BDTTQx andPC₁₂BDTFTQx are a type of photovoltaic materials with high mobility.In chapter4, PFOTQx, PFOFTQx, PCzTQx and PCzFTQx are afforded by Suzukicoupling reaction using quinoxaline or fluorinated quinoxaline derivatives as acceptorand fluorene and carbazole as donor. Synthetic polymers have high thermal stability and reasonable absorption, the HOMO level energy of fluorinated polymer is lowerthan that of without fluorine atom. Under the same conditions, the device based onfluorinated material has high Vocand the PCE increases about15%-33%.In chaper5, two polymers based on quinoxaline-thiophene （TQ） and fluorinatedquinoxaline-thiophene （FTQ） are synthesized using Stille coupling reaction,respectively. The absorption and electrochemical results are similar to the previouschapters. The photovoltaic property of FTQ is studied carefully and a higher PCE of5.3%is obtained after the annealing of active layer.In chapter6, it contains the summary of work and outlook of later work.