Synthesis And Design Of Organic Photosensitizer Based On Fused Thiophene Connecting And Their Photovoltaic Performance

Energy crisis has become a major problem in today’s society, nearly three centuries, theIndustrial Revolution led to the mechanization of large-scale production makes our increasingdemand for energy, so non-renewable fossil fuels play an important role ,after the oil crisis inthe1970s, energy demand is growing day by day.Solar energy is a renewable energy, has advantages over other energy sources: 1)compared with fossil fuels, solar energy is an inexhaustible renewable energy; 2) comparedwith nuclear energy, solar energy is safe and clean; 3) compared with water, wind, solarenergy is easy to be used, less depend on geography, low-cost. In 1954, the practical siliconsolar cells has been produced, but it has a high-cost and complex preparation process, Until1991, Swiss scientists Gr tzel and his group developed an overall power conversionefficiency approaching 7%,（Dye-Sensitized Nanocrystalline Photovoltaic Solar Cells，DSSC）the process is simple, low-cost, longer life. The core of these cells is photosensitive dye,which directly determines the performance of dye-sensitized solar battery life andphotoelectric conversion efficiency,In this paper six new dyes has been designed and synthesized, the first five are based onsingle Hexyloxyazobenzene triphenylamine as electron dornner, the sixth with a doubleHexyloxyazobenzene triphenylamine as electron donner, with three different fused thiopheneconnecting epoxy thiophene as conjugation bridge, cyano acetic acid as the electron acceptor,to given a D-π-π-A type of dye. starting with iodine to phenol, thiophene, n-C₆H₁₂Br, 3 -bromothiophene and n-C₃H₇Br, through NBS or Br₂bromination, Suzuki coupling reaction,Stille coupling reaction, Vilsmeier-Haack reaction and Knoevenagel condensation and end upwith the target compounds, during the synthesis, the non-reported 29 intermediate and finalproducts were introduced IR, melting point,¹³C NMR,¹H NMR and MS. We then carried outresearch on these dyes ,like optical properties, molecular theoretical calculations andpreparation into sensitized photovoltaic performance of solar cell, summed up the structure ofthese dyes and the relationship between the photoelectric conversion efficiency of thebattery ,laid the foundation with design of efficient dye for the future.The four kinds of dye-XS35 38，Which is based on push-pull electronic melt thiopheneand ethylene thiophene as conjugated bridge, all those four dyes at 500 nm has a strongabsorption band, the wavelength of maximum absorption peakλmax located at 514, 497,492and 494 nm, the HOMO and LUMO of these four dyes match with titanium dioxide energylevel and electrolyte energy level, it is necessary to be as a sensitizer, the electrochemicalimpedance spectroscopy study shows, the RCT of TiO₂/ dye / electrolyte interface: XS38> XS35> XS36> XS37; electron lifetime: XS38> XS35> XS36> XS37. Finally, the standardAM 1.5 illumination, through research with the six dye-based photovoltaic performance ofDSSCs: in the XS35-XS38, XS38-sensitized solar cell performance better than the XS35-37,short-circuit current density （JSC） 14.47 mA cm-2, open circuit voltage （VOC） 670 mV, fillfactor （ff） 0.63, photoelectric conversion efficiency （η） of 6.11%; dyes C83 and C84 are singleand dual supply structure, these two dyes were tested in the paper, it turms out that: C83photovoltaic performance better than C84, short-circuit current density （JSC） 9.94 mA cm-2,open circuit photovoltage （VOC） 585 mV, fill factor （ff） of 0.62, photoelectric conversionefficiency 3.62% ,under the same conditions N719 dye-sensitized solar cell efficiency of 7.36.The structure of these dyes and the relationship between the photoelectric conversionefficiency of the battery laid the foundation with design of efficient dye for the future.