Novel Ionic Liquids Electrolytes For Efficient Dye-sensitized Solar Cells

With the increase of population and energy consumption,the demand for energy is rising.Because of the non renewable property of traditional energy,people have been pursuing the development of new renewable energy sources,such as wind energy,tidal energy,hydraulic energy,wave energy,ocean thermal energy and so on.One representative is solar energy.It is inexhaustible,and it will also not cause any environmental pollution and ecological imbalance.In addition,solar energy,such as wind,water,etc.will be subject to geographical constraints.Dye sensitized solar cells,as one kind of high efficiency photoelectric conversion device,has been widely studied.In 1991,M.Gr?tzel et al made a revolutionary breakthrough in dye-sensitized solar cells.They used Ru metal containing dye Z907-sensitized TiO₂ film as photoanodes,the dye-sensitized solar cell had novel structure,and a high photoelectric conversion efficiency of 7.1%was gained.As one of the most important components,electrolyte plays a decisive role in the photoelectric conversion efficiency of dye-sensitized solar cells.The traditional electrolyte materials are organic liquid materials.Thus,these organic liquids are highly volatile,unstable and easy to leak.In addition,there is also some electronic recombination on the interface.They are certain safety loophole for long-term use of dye-sensitized solar cell devices.In this paper,we did a series of work related to the scientific problems mentioned above,such as improving the conductivity of the electrolyte,introducing the co-adsorbent to improve the usage of sun light and decrease the aggregation of dye molecules.We mainly designed and synthesized some functional ionic liquid.Finally,we explored their application in dye-sensitized solar cell devices.The main research work contained the following four parts:1.High conductive carbon nanotubes were introducing into the plastic crystals in P₁₂I.The effect of carbon nanotubes on plastic crystal surface morphology,thermal stability,ionic conductivity and ion diffusion coefficient I^-/I₃^-effect.The results show that the introduction of CNTs does not affect the thermal stability of P₁₂I,but it can improve the conductivity and increase the diffusion rate of I^-/I₃^-ions.Finally,we use it as the electrolyte material of dye sensitized solar cell,and the photoelectric conversion efficiency is up to 5.6%.At the same time,the battery can effectively overcome the problems of electrolyte leakage and volatilization,which provides a new idea for the preparation of high efficiency dye-sensitized solar cell devices.2.Multi-iodine doped imidazole crown ether functionalized ionic liquids was designed and synthesized,named[12-C-4][Im].The thermal stability of was[12-C-4][Im]detailedly studied.When introducing lithium iodide or iodide magnesium iodide,the ionic conductivity of the electrolyte materials could effectively improve.In addition,when applied in the dye-sensitized solar cells,devices based on lithium iodide-doped or magnesium iodide-doped ion liquid displayed higher photoelectric conversion efficiency than that of devices based on pure[12-C-4][Im].These results indicate that doping can effectively improve the ionic liquid ionic conductivity.It provides a new method for the preparation of novel ionic liquid electrolyte materials.3.At room temperature,mixing of four kinds of solid ionic liquid?DMII,EMII,MPI and EPI?leaded to one kind of solvent free liquid ionic liquid materials.The thermodynamic analysis test of the ionic liquid had been carried out.The results showed that it has good thermal stability and excellent ionic conductivity.When used as electrolyte for dye-sensitized solar cell devices,the fabricated cell device exhibited high photoelectric conversion efficiency and good long-term stability.The results show that this method can be used to prepare safe and effective ionic liquid electrolyte.4.A cyano biphenyl derivatives with light-scattering properties was synthesized,named as CBHA.When used as a co-adsorbent,CBHA and dye molecules could be adsorbed on the surface of the titanium dioxide anode.The loading of the dye reduced,and the possibility of the dye molecule aggregation could be effectively reduced.On the other hand,due to the light scattering,CBHA could reflect the sunlight,which was not absorbed by the dye for a second use,finally improving the utilization rate of the sunlight.After the introduction of CBHA,the photoelectric conversion efficiency of the dye-sensitized solar cells improved effectively.It provides a new method for the preparation of high efficiency dye-sensitized solar cell devices.