Synthesis And Performance Of Novel Fluorinated Donor Materials In Solar Cells

Organic Polymer solar cells have been caused extensive attraction due to their own unique performance, such as low cost, light weight, simple fabrication process and controllability of materials’ structure. Although photoelectric conversion efficiency(PCE) of OPSCs has been over 10% in recent years, a variety of touch issues should be resolved for commercial use. The key constraints factors are focusing on narrow photo response region of donor materials, unmatched energy levels of donor-acceptor materials and low mobility of electron and hole, which impede the improvement of PCE. So, it is necessary and primary approach to design and synthesize novel conjugated copolymers with unique performance to improve PCE. In this dissertation, the study mainly concentrates on carbazole, benzo[1,2-b:4,5-b’]thiophene, fluorinated benzothiadiazole and thieno[3,4-c]pyrrole-4,6-dione, several different fluorinated conjugated polymer donor materials of solar cells had been synthesized and characterization. The primary research contents are shown as follows:1. In chapter 2, a novel fluorinated dithienyl benzothiadiazole derivative(DTff BT) was synthesized, and then three kinds of alkyl carbazole as donors were introduced into the DTff BT unites via Suzuki coupled reaction. A series of conjugated polymers(PCDTff BT) were prepared and characterized by fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(1H NMR) and gel permeation chromatography(GPC). Besides, their thermal stabilities, photophysical and electrochemical properties were analyzed. The results showed that every copolymer has higher molecular weight, excellent thermal stability and low optical band gap(about1.95 e V). Suitable HOMO energy levels measured and calculated by cyclic voltammetry were about-5.20 e V. Hence, those conjugated copolymers are hesitated to manufacture OPSCs as donor materials.2. In chapter 3, a kind of acceptor unite thieno[3,4-c]pyrrole-4,6-dione(TPD) was synthesized, then three kinds of alkyl carbazole as donors and DTff BT as acceptor were introduced into the TPD unite via Suzuki coupled reaction. A series of conjugated terpolymers(PC-DTff BT-TPD) were prepared and characterized by fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(1H NMR) and gel permeation chromatography(GPC). Besides, their thermal stabilities, photophysical and electrochemical properties were analyzed. The results showed that those three kinds of terpolymers have higher molecular weights and excellent thermal stabilities. The absorbance range was existed in 400~600 nm, and the HOMO energy level and LUMO energy level were about-5.20 e V and-3.30 e V, so they have the potential to be used as a OPSCs donor materials.3. In chapter 4, a kind of donor unite benzo[1,2-b:4,5-b’]thiophene(BDT) was synthesized, then TPD and DTff BT as acceptors were introduced into the BDT unite via Suzuki coupled reaction. A series of conjugated terpolymers(PBDT-DTff BT-TPD) were prepared and characterized by fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(1H NMR) and gel permeation chromatography(GPC). Besides, their thermal stabilities, photophysical and electrochemical properties were analyzed. The results showed that every copolymer has higher molecular weight, excellent thermal stability. With the increase of TPD unite in polymer backbone, photoabsorption region of polymers was further broadened to 750 nm, the absorption bands of copolymers spanned nearly the wide range of visible spectra, which matched to the solar spectra and increased greatly solar utilization rate. Suitable HOMO energy levels and LUMO energy levels measured and calculated by cyclic voltammetry were about-5.32 e V and-3.53 e V, respectively. Therefore, they have the potential to be used as donor materials in the application of conjugated polymer solar cells.