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染料敏化太阳电池电解质材料的制备与性能研究

Prepration of Electrolytical Materials of Dye Sensitized Solar Cells and Study of Their Characters

【作者】 杨燕珍

【导师】 吴玉程;

【作者基本信息】 合肥工业大学 , 材料学, 2013, 博士

【摘要】 染料敏化太阳电池(DSSCs)具有成本低、效率高、制作工艺简单等优势,引起了众多科研工作者和工业界人士的关注。在DSSCs中,离子液体和添加剂作为电解质的重要组成部分,对DSSCs光伏性能的提高起着至关重要的作用。本论文旨在发展环境友好型离子液体的制备方法、开发适用于DSSCs的新型离子液体和添加剂等电解质材料,以期获得高效、稳定的染料敏化太阳电池。主要研究内容如下:利用高压釜制备了3-甲基苯并噻唑碘(MBTI)和2,3-二甲基苯并噻唑碘(DMBTI),利用热分析法研究了苯并噻唑环上引入2位甲基对其熔点和热稳定性的影响;利用加热回流法合成了一碘化N-(2-羟乙基)乙二胺盐(HEEDAI);将MBTI、DMBTI、苯并噻唑(BT)、2-甲基苯并噻唑(MBT)和4-叔丁基吡啶(TBP)作为染料敏化太阳电池(DSSCs)电解质溶液中的添加剂,制备了含有不同添加剂的电解质材料;研究了含有不同质量的乙腈(ACN)和3-甲氧基丙腈(MePN)以及不同质量的1,2-二甲基-3-丙基咪唑碘(DMPII)和1-甲基-3-丙基咪唑碘(MPII)电解质材料的性能。并将这些电解质材料应用于DSSCs中,利用超微铂电极和循环伏安法以及电化学阻抗谱法研究电解质材料中不同化合物的阳离子结构、杂环结构和杂原子N和S以及不同电解质组成对I-3和I-的氧化还原行为和铂电解质界面的影响;并将这些电解质材料组装成DSSCs,测量了光伏性能。结果表明:利用高压釜合成苯并噻唑碘,操作简便、缩短了反应时间、提高了产率;在苯并噻唑环上引入2位甲基,可以提高苯并噻唑碘的熔点和热稳定性;DMBT+易在电极上形成多层吸附,且DMBT+对I-的束缚力小,因此I-的扩散系数较大;对不同添加剂的研究结果表明,含有碱性N原子的添加剂对DSSCs光伏性能作用优于碱性S原子的添加剂;含有吡啶环结构添加剂(TBP)对DSSCs光伏性能作用优于含有苯并噻唑环的添加剂(MB、MBT、MBTI、DMBTI),且DMBTI可以作为一种良好的添加剂应用于DSSCs中;HEEDAI作为电解质中的I-源,所组装的离子液体基DSSCs,具有较高的开路电压和填充因子。以DMPII作为I-供体、ACN和MePN的质量混合比为2:1时,电解质溶液中I-3和I-具有较大的表观扩散系数,且对应的DSSCs具有较高的光电转换效率;当ACN和MePN的质量混合比为2:1、DMPII和MPII以2:1混合作为I-源时,DSSCs具有较高的短路电流密度和光电转换效率。进一步研究了碘化-(2-羟乙基)乙二胺盐(HEEDAIs)和碘化-(2-羟乙基)哌嗪盐(HEPIs)的合成以及热稳定性,并研究了二元离子液体中HEEDAIs和HEPIs对I-3离子和I-离子氧化还原电对的影响。结果表明HEEDAIs可以抑制基体TiO2导带中释放的电子与I-3离子的复合,从而使HEEDAI可以成为染料敏化太阳电池电解液中添加剂4-叔丁基吡啶。电解液组分为0.15mol L-1I2,HEEDAI与MPII质量比为1:4时,由此而组装成的染料敏化太阳电池短路光电流密度为9.36mA cm-2,开路光电压为0.67V,填充因子为0.52,在光照下,染料敏化太阳电池的光电转换效率为3.24%。

【Abstract】 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.

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