Study On Photoelectric Properties Of Dye-Sensitized Solar Cells Based On Thixotropy Electrolyte And Porphyrin Dyes

Nowadays, dye-sensitized solar cell (DSSC) is of great interest because of its relatively low cost and reasonably high efficiency. The energy conversion efficiency of DSSCs has already reached to as high as 11.2%. However, as a complex system for DSSCs, there are still many important unsolved issues, such as device sealing and stability caused by liquid electrolytes and expensive sensitizers. Recently, many efforts are more focusing on new type dye and quasi-solid or solid electrolyte research. However, the photoelectric conversion efficiency of DSSCs based on quasi-solid or solid electrolyte are relatively low because these electrolytes can not full into porous films with leading to the interfacial bonding was poor and its ionic mobility is relatively low. In this dissertation, based on the idea of seeking new type electrolyte and developing new type dye, we prepared blood mimetic thixotropy electrolyte by sol-gel method, and applied it into quasi-solid DSSC. Porphyrin derivatives with containing azobenzene functional group were also synthetized and applied into liquid state DSSC. The main work is concentrated on the following aspects:Nanometer TiO2 sol for coating film was prepared by cooperating hydrothermal colloidal sol with organic polymer dispersing agent (PVA). Nanocrystalline TiO2 porous films were prepared by using electro-hydrodynamic technique (EHD), and the characteristics of the films are investigated by using TEM, SEM and optical spectrum.etc. The results show the films prepared by EHD technique have multilevel hierarchical structure, therefore, better optical scattering properties.Three different constituent quasi-solid electrolytes with blood mimetic thixotropy were prepared by cooperating ionic liquid electrolyte with nanometer TiO2 colloidal sol synthetized by sol-gel method. The new type electrolytes were measured in thixotropy, thermostability, ionic conductivity and wetting property, etc. The results indicated the blood mimetic thixotropy electrolytes show the better thermostability, higher ionic conductivity and higher fill property in porous films.Blood mimetic thixotropy electrolytes are adopted in DSSCs and their photophysical and electrochemical properties are studied. Under under an AM-1.5 illumination at 100 mW/cm2, the overall energy conversion efficiency of 6.45%, 6.36% and 5.7% are obtained for the DSSC devices of TPNE1, TPNE2 and TPNE3, respectively, and the higher fill factors (≥0.70) are obtained. Measured in 10 days, the DSSC devices of TPNE1, TPNE2 and TPNE3 show higher stability than that of device with ionic liquid electrolyte without any sealing. The results of electrochemistry impedance analysis indicate these thixotropy electrolytes show the equal charge transmittablity relative to ionic liquid electrolyte.By molecular structure optimizing, we successfully synthetized H2P and ZnP porphyrin derivatives with containing azobenzene fuctional group. Introducing of azobenzene group can enhanceπ-conjugated system of porphyrin derivatives, and phenolic group in the terminal group of azobenzene acts as the anchoring group of TiO2 surface. We also verified two prophyrin derivatives can serve as the photosensitizer for DSSC by optical spectrum and cyclic voltammetry measurements.Two porphyrin derivatives are applied as photosensitizers for fabrication of liquid DSSCs based on TiO2 photoelectrode, and the performances of cells are explored. Under illumination of simulated AM-1.5 solar light (100mW/cm2), the short-circuit current density of 14.6 mA/cm2 and the overall energy conversion efficiency of 4.37% are obtained with the maximum IPCE value of 75% for the device of ZnP. Especially, the high short-circuit current density is the highest one reported to our knowledge.