Photovoltaic Performance Research Of Dye-Sensitized Solar Cells Based On Quasi Solid-State Electrolyte

With the rapid development of human society, the traditional energy fuel consumption and demand have increased dramatically, and the resulting global warming and energy crisis have become our problem to be solved. Therefore, the development of renewable energy technology becomes the first assignment of in the energy industry. Among the green renewable energy, solar energy is clean, environment friendly and inexhaustible. There are many advantages in solar photoelectric conversion, so the development of solar photovoltaic technology has been received great attention. One important application of solar photovoltaic mode is the development and utilization of solar cells. In recent years, the third generation solar cells-dye-sensitized solar cells （DSCs）, has attracted wide attention of the application research by many researchers around the world. Typical dye-sensitized solar cell is made of photoanode, dye sensitizer, liquid electrolyte and counter electrode. However, the traditional electrolytes of DSC are liquid, which is easy to volatilize, leak and rust electrode. In addition, the toxic solvent in the liquid electrolyte is also a factor that limits its commercial application. As a result, the long stability of the DSC can not be guaranteed. Therefore, in order to achieve practical application of DSCs, research on strong quasi-solid or solid electrolytes with strong stability and high ionic mobility is becoming a hot spot of research in recent years. In this study, the key issues are around the construction of a quasi-solid-state DSC based on ZnO or TiO₂ as photoanodes; mainly for building quasi-solid-state electrolytes, optimizing process of devices integration, improving the conversion efficiency and stability of quasi-solid-state DSC, and the details are as follows:1. A gel-state electrolyte was builded by using polystyrene （PS） as gelata, and then we optimized the ratio of acetonitrile and valeronitrile in the electrolyte to bulid quasi-solid state ZnO-DSC. The results indicated that when the volume ratio of acetonitrile and valeronitrile was controlled to be 85:15, the conversion efficiency reached to be 4.08%, compared to the efficiency of DSC with liquid electrolyte （4.12%）, the efficiency is almost no attenuation. In addition, after 20 days’stability test, the efficiency of DSC with quasi-solid state electrolyte only decayed 7% in indoor condition and 12% in outdoor condition, but the efficiency of DSC with liquid electrolyte decayed 27% and 37% in the same condition. The results showed that compared to liquid electrolyte, the design of the quasi-solid electrolyte, not only keeps the conversion efficiency of DSC with liquid electrolyte, but also enhances the stability of the DSC; there has a certain guiding significance to the practical application of solar cells.2. A composite of graphene （Gra） and polystyrene nanobeads （PS） quasi solid-state electrolyte was prepared and successfully applied into DSC. It was found that:l) When the doping amount of Gra was 12 mg/mL, the conductivity of quasi solid-state electrolyte increased from 32.8 mS/cm to 39.8 mS/cm; 2) Due to the increase of the conductivity of the electrolyte, the short-circuit current density of quasi-solid DSC increased from 13.86 mA/cm2 to 18.86 mA/cm2, and the conversion efficiency increased from 4.09% to 5.08%; Electrochemical impedance test showed that the electron transport in the DSC enhances after addition of graphene, and reduces the electron transfer impedance; 3) Assembly the DSC with the quasi solid-state electrolyte doping amount of 12 mg/mL, and test the long term stability; the result showed the efficiency of DSC based on ZnO with Gra and PS nanobeads composite electrolyte can maintain over 90% of its initial efficiency in outdoor condition after 1000 h, revealing its superior long-term durability. This result is important for the practical application of DSC based on quasi solid-state electrolyte.3. Constructing TiO₂ photoanode modified by Au, and then gold nanoparticle with TiO₂ as composite photoanode was prepared by the method of self-assembly. The microstructure characterizations of TEM revealed that the size of the Au nanoparticle is about 6 run. Ultraviolet spectrum showed that Au/TiO₂ composite photoanode revealed stronger light absorption in 520-600 nm range. Photoelectric properties test shows that under the optimization concentration of the self-assembly precursor HAuCl₄-3H₂O （80 μg/mL）, compared to TiO₂-DSC, conversion efficiency of Au/TiO₂ based DSC reached 10.02%, and the short-circuit current density increased 14%. Then the Au/TiO₂ composite photoanode was applied to quasi solid-state DSC based on polyoxyethylene （PEO） as gel, and conversion efficiency reached up to 8.12%. The above results show that composite photoanode film exhits light absorption enhancement in 520-550 nm range of the visible light due to the plasma effect of gold nanoparticle, and the conversion efficiency of DSC had a larger increase. When combined with quasi-solid electrolyte, the efficiency also shows a good effect. These results should provide an effective way for the practical application of quasi solid-state DSC.