| Solar energy has always been widely concerned as an abundant, clean and pollution free energy. In1991, nanocrystalline semiconductor TiO2was introduced into Dye-Sensitized Solar Cells (DSSCs) for the first time by Swiss scientist Michael Gratzel and Brian O’Regan, and the photoelectric conversion efficiency of this kind of solar cells was improved greatly. Great progress was achieved in the R&D of DSSCs in the past two decades. Owing to their simple fabrication as well as low-cost production, DSSCs were known as the third generation solar cells, which have become competitive alternatives to conventional solar cells. Dye sensitizers are one of the core components of DSSCs as well as the larger portion of the cost. Currently, polypyridyl ruthenium complexes (including N3and N719) are widely used in laboratory-scale devices for their high efficiency and long-term stability, and a highest record efficiency of up to11.5%was achieved by dye CYC-B11. While ruthenium is a kind of precious metal elements and the core ligand4,4’-dicarboxy-2,2’-bipyridine is expensive for preparation, it is urgent to design new sensitizers with higher photoelectric performance and develop a cost-effective process for synthesizing ruthenium-based dye.In this paper, we investigated the design idea of new ruthenium-based sensitizers and the synthesis process of ruthenium-based dye with both theoretical and experimental method. The works can be divided into three parts.In the first part of this paper, the effect of alkyl chain of ruthenium-based dyes on DSSCs was investigated by density functional theory (DFT) and time-dependent DFT methods. Two important parameters of the solar cells, the short-circuit current density (Jsc) and open-circuit voltage (Voc), were theoretically characterized. Light-harvesting efficiency and driving force of electron injection (△Ginject.) were calculated to provide an insight into Jsc. A simple and effective dye-titanium dioxide model, adopted to simulate the interfacial interaction between dye and semiconductor, was applied to ruthenium dyes for the first time. The vertical dipole moments and the number of electrons transferred from the dye to TiO2were investigated for understanding Voc. Jsc and Voc were found to increase when the alkyl chain increase from1to13carbons, whereas a decrease was seen for Voc at the chain length of18carbons. The calculated results are in considerable agreement with published experimental data and this calculation model is reliable and reasonable for understanding ruthenium dyes.In the second part, we designed newly high effective sensitizers based on the verified calculation model. Thiophene functional group has a good performance in the ruthenium-based dye, we adopted the above model to theoretical characterize the dyes containing various thiophene group which have been experimental synthesized. Based on the experimental data and theoretical analysis, we can control the effect of these functional groups on the optical properties of dyes. Through analysis and comparison, we found that the dye A-1containing three thiophene groups has better theoretical performance, which is expected to have outstanding optical performance in the experiment.At last, the core ligand of ruthenium-based dye was prepared with a simple and economic process, in which industrial2-chloroisonicotinic acid was the raw materials, glycerol/water mixtures were used as solvent and Pd/C (mass fraction of10%) as the catalyst. With the mild conditions, high yield and recyclable catalyst, this process route is expected to achieve industrialization. The core ligand was reacted with RuCl3·3H2O under the condition of darkness, high temperature and N2atmosphere, then the chlorine of this ruthenium complexes was substituted by SCN group of Potassium thiocyanate. The N3dye was synthesized with the one-pot process.This route can be used in preparing the ruthenium-based dyes with similar structure. |
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