Synthesis And Photovoltaic Properties Of Hyperbranched Polymers With D-π-A Architecture And Linear Organic Dyes With Double Electron Donors

In this dissertation, the basic knowledge of dye-sensitized solar cells (DSSCs) was briefly described, and the research progress of photosensitizers was summarized in detail. The photosensitizer was a vital factor to improve the power conversion efficiency of DSSCs. As a result, this dissertation is focusing on the design and synthesis of series of new hyperbranched polymers with donor-Ï€-acceptor (D-Ï€-A) architectures and linear organic dyes with double electron donors (D-D-Ï€-A). The structures of the as-synthesized hyperbranched polymers and linear organic dyes were confirmed by 1H-NMR, FT-IR and MALDI-TOF. The photophysical, electrochemical and photovoltaic properties of the hyperbranched polymers and linear organic dyes have been researched by UV-vis spectra, PL spectra and Cyclic Voltammetry. In addition, the photovoltaic performances of DSSCs based on the as-synthesized hyperbranched polymers and linear organic dyes were invesitgated. The main results are as following:1. Three novel hyperbranched polymers (H-tpa, H-cya and H-pca) with the same conjugated core structure and different functional terminal units were synthesized according to the A3+B2 type Wittig-Horner polymerization method. The effect of different functional terminal units on the photophysical, electrochemical and photovoltaic properties had been investigated. The study results showed that the donor-Ï€-acceptor architecture in hyperbranched molecule benefited intramolecular charge transfer and consequently increased the generation of photocurrent and the three-dimensional steric configuration can effectively retard the aggregation of dyes on TiO2 film. Among the three hyperbranched polymers, the highest power conversion efficiency of 3.93% (Jsc = 8.78 mA/cm2, Voc = 0.65 V, FF = 0.688) was obtained for H-pca based DSSC under simulated AM 1.5 G solar irradiation (100 mW/cm2).2. Three novel linear organic dyes (SD6~SD8) with double electron donors (D-D-Ï€-A) were designed, synthesized and applied in DSSCs by a series of classic organic reactions such as Suzuki couple reaction, Stille couple reaction, Knoevenagel condensation reaction. The effects of different double electron donors on the photophysical, electrochemical properties and photovoltaic performance were systematically studied. The research indicated that the dyes with double donors exhibited the broaden absorption spectra and the improved ability of harvesting sunlight. Among the three dyes, a maximum power conversion efficiency of 7.03% was obtained under simulated AM 1.5 G 100 mW/cm2 solar irradiation with the DSSC based on SD6 dye (Jsc = 14.25 mA/cm2, Voc = 0.70 V, FF = 0.705), and it exhibited the best light capture ability with the highest incident photon-to-current conversion efficiency (IPCE) of 73% at 427 nm.