Prepration Of Electrolytical Materials Of Dye Sensitized Solar Cells And Study Of Their Characters

Dye sensitized solar cells (DSSCs) have attracted great attention in the past time due to theirlow cost, high efficiency and simple manufacturing process in the field of research and industry.Ionic liquid and additives are two important constitutes of the electrolyte and play the crucial role inthe improvement of photovoltic performance of DSSCs. In this dissertation, the fabrication methodof environmentally friendly ionic liquid was investigated. And novel ionic liquid and additives usedfor DSSCs were also developed to get DSSCs with high efficiency and stability. The main researchcontents are as follows:3-methyl benzothiazoliumiodide (MBTI) and2,3-dimethyl benzothiazoliumiodide (DMBTI)were prepared using Teflon-lined, stainless steel autoclaves. The influence of the2-position methylgroup of the benzothiazolium heterocycle on the melting point and thermal stability ofbenzothiazolium iodides was studied by thermogravimetric analysis and differential scanningcolorimetry. N-(2-hydroxyethyl) ethylenediaminium iodide (HEEDAI) was also synthesized. MBTI,DMBTI, benzothiazole (BT),2-methyl benzothiazole (MBT),4-tert-butylpyridine (TBP) were usedas additive in electrolyte of dye sensitized solar cells (DSSCs). The electrolytes were prepared withdifferent ratio of1,2-dimethyl-3-propylimidazolium iodide (DMPII),1-methyl-3-propylimidazoliumiodide (MPII),3-methoxypropionitrile (MePN) and acetonitrile (ACN). Moreover, the influence ofdifferent electrolytes with the heterocyclic structure and heteroatom N/S or different composition onI3–/I–redox behavior and the Pt electrode/solution interface reaction was investigated by cyclicvoltammetry using a Pt disk ultramicroelectrode and electrochemical impedance spectroscopy.DSSCs were assembled, and their photovoltaic performances were also studied.The results revealed that the preparation of the benzothiazolium iodides is simple with shortreaction time, easy purification, and high yields. The2-position methyl group of DMBTI has ahigher melting point and excellent thermal stability than MBTI. Compared with MBTI, the apparentdiffusion coefficient of I–in solution with DMBTI was higher. From the photovoltaic performance ofthese DSSCs, it was concluded that pyridine cycle (TBP) was better than benzothiazole cycle (MB,MBT, MBTI, DMBTI) and basic N atom was better than basic S atom in these additives. The DSSCswith HEEDAI gave higher open voltage and fill factor. Furthermore, the apparent diffusioncoefficient of I–/I–3and the photovoltaic performance of DSSCs were higher than others, when theDMPII was I–source of the electrolyte and the weight ratio of ACN and MePN was2:1. The DSSCswith DMPII and MPII (weight ratio2:1), ACN and MePN (weight ratio2:1) as solvent gave higheropen voltage and fill factor.Finally, N-(2-hydroxyethyl) ethylenediaminium iodides (HEEDAIs) and N-(2-hydroxyethyl)piperazinium iodides (HEPIs) were synthesized, and their thermal properties were analysed. Theinfluence of HEEDAI and HEPI on I－3/I－redox behavior in binary ionic liquid was investigated. The result revealed that HEEDAI can suppress the recombination between I－3and the injectedelectrons in TiO2conduction band and be used as the alternative of4-tert-butylpyridine in theelectrolyte of dye-sensitized solar cells. The electrolyte C,0.15mol·L1I2, HEEDAI and MPII withmass ratio of1:4, gave the short-circuit photocurrent density of9.36mA·cm2, open-circuitphotovoltage of0.67V, fill factor of0.52, and the corresponding photoelectric conversion efficiencyof3.24%at the illumination.