Synthesis And Application Of Ruthenium Sensitizers With High Molar Extinction Coefficient

In this thesis,by introducing thiophene,furan,3,4-ethylenedioxythiophene (EDOT),thieno[3,2-b]thiophene,and dithieno[3,2-b:2',3'-d]thiophene units in order to extend theÏ€conjugation of spectator ligands,we have synthesized five new heteroleptic polypyridyl ruthenium complexes coded C101-C105 with high molar extinction coefficients to enhance the optical absorptivity of mesosporous titania film and charge collection yield in dye-sensitized solar cell,further,to prepare higher effective dye-sensitized solar cells.The sensitizers' molar extinction coefficients,emission spectra,anchored modes on the surface of TiO₂ film,the redox potentials were studied by using of UV-vis,spectrofluorometer,ATR-FTIR and cyclic voltammetry.The devices efficiencies,photovoltaic characterization and stability were also tested.It demonstrated that the molar extinction coefficients(ε) of the low-energy MLCT absorption bands for C101,C102 and C104 are 17.5 M^-1·cm^-1,16.8×10³ M^-1·cm^-1,and 20.5×10³ M^-1·cm^-1,respectively.The redox potentials of the ruthenium center in sensitizers determined by ultramicroelectode square-wave volammetry are 0.904 V,0.919 V,0.901 V,0.961 V and 0.942 V(vs NHE), which are all higher than that of the iodide electron donor,providing ample driving force for efficient dye regeneration,avoiding the geminate charge recombination.According to the tests of devices' efficiencies,photovoltaic characterations and stabilities,along with an acetonitrile based electrolyte,the C101 sensitizer has already achieved a strikingly high efficiency of 11.0%～11.3%even under a preliminary testing.More importantly,based on a low volatility 3-methoxypropionitrle electrolyte and a solvent-free ionic liquid electrolyte cells having corresponding＞9.0%and～7.4%efficiencies retained over 95%of their initial performances after 1,000 h full sunlight soaking at 60℃.The more striking is that with this C101 sensitizer,several new DSSC benchmarks under the air mass 1.5 global(AM 1.5G) sunlight have been reached.The preliminary tests show that for a newly developed C104 dye,the achievement of over 10.5%power conversion efficiencies is very encouraging,and we will further systematically optimize the cell parameters of different DSCs to take the full potential of this promising sensitizer with enhanced optical absorptivity.With the aid of electrical impedance measurements we further disclose that compared to the cell with an acetonitrile based electrolyte,a dye-sensitized solar cell with an ionic liquid electrolyte shows a feature of much shorter electron diffusion lengths due to the lower electron diffusion coefficients and shorter electron life times,explaining the photocurrent difference between these two type devices.This highlights the necessary efforts to further improve the efficiency of cells with ionic liquid electrolytes,facilitating the large-scale production and application of flexible thin film mesoscopic solar cells.