【作者】 刘婧；

【导师】 孙立成； 杨希川；

【作者基本信息】 大连理工大学 ， 精细化工， 2013， 博士

【摘要】 光敏剂在染料敏化太阳能电池中起到吸收光子,并将光子转换成电子的作用,是电池的重要组成部分。发展新的光敏剂对于提高染料敏和太阳能电池的光电转换效率十分有利。早期对光敏剂的研究集中在金属配合物染料上,但是由于这类染料自身存在一些问题,人们逐渐将目光转移到摩尔消光系数较高、合成简单和结构多样的纯有机光敏剂。经过不断地发展,纯有机光敏剂已经取得长足发展。尽管如此,大部分纯有机光敏剂对近红外光区的光响应较弱,因此发展高效的纯有机近红外光敏剂对于进一步推动纯有机光敏剂的应用十分重要。首先,在高效吩噁嗪纯有机光敏剂TH305中引入π-桥基设计合成了3个染料,LJ101、LJ102和LJ103,π-桥基的引入有效地拓宽了光谱吸收。利用质谱、氢谱等手段对分子结构进行鉴定,并对染料的光物理和电化学性质进行了研究。将光敏剂应用于染料敏化太阳能电池,研究染料结构与电池性能之间的构效关系以及电池内部电子传递过程。与TH305相比,延长分子的共轭体系能够使染料分子的光谱吸收发生红移,但是同时降低了染料的LUMO能级,减小了激发态染料将电子注入到TiO2的驱动力,从而影响电池效率。因为卟啉类分子在500-700nm范围内有中等强度的吸收,并且卟啉分子具有可延长的共轭结构,因此受到广泛关注。由此本文设计合成了3种带轴向吸附基团的硅卟啉类光敏剂,LJ201、LJ202和LJ203,并对其结构进行了质谱和氢谱的表征,而后又进行了光物理和电化学性质的研究。通过测试不同CDCA浓度下,染料吸附在Ti02表面后的紫外可见吸收光谱发现,由于LJ201、LJ202和LJ203是通过轴向吸附方式吸附在Ti02上,避免了染料在膜上的聚集,因此在后续的电池测试中,没有使用CDCA做共吸附剂。将这3个染料用于染料敏化太阳能电池后,研究电池的光伏性能。由于三苯胺独特的螺旋桨结构可以抑制电子复合,LJ203获得了最高的光电转换效率。利用红外光谱研究染料吸附方式时发现,LJ201之所以表现出较差的光伏性能是因为其吸附方式是单齿,单齿吸附影响了其电子注入效率。电解质作为传递电子的媒介对电池性能产生很大影响。常用的I-/I3-液态电解质在可将光区有很强的吸收,并且在大面积电池的应用中会腐蚀电池中使用的金属,也会因溶剂挥发等问题对电池的封装造成影响,因此开发可替代的电解质十分有意义。在本论文中,S2-/Sx2-和I-杂合离子液体电解质分别与金属配合物光敏剂和纯有机光敏剂组装成电池。研究电池的光伏性能,以及电池内部电子的传递情况后发现,相比于I-/I3-电解质,这种杂合电解质几乎不吸收光,并且不论在金属配合物光敏剂敏化的电池还是纯有机光敏剂敏化的电池中均能够取得良好的实验结果。通过测试不同光照下的电池性能发现,这类杂合离子液体电解质在1个标准光强下与低光照下获得同样良好的光伏性能。最后本论文中还设计合成了一类I-/邻苯醌杂合电解质,研究了其在染料敏化太阳能电池中的应用情况。这类电解质由于存在电子复合问题,在染料敏化太阳能电池中的应用仍需要进一步的研究。更多还原

【Abstract】 Among the components of dye-sensitized solar cells (DSCs), sensitizers play a vital role in the light-harvesting and converting photon to electron. The development of new sensitizers for DSCs is very important to improve the overall efficiency of the cell. In the early research, the focus was mainly on metal complexes as sensitizers. Lately since some disadvantages of metal complexes, more attention has been paid to metal-free organic dyes due to their high molar extinction coefficients, easy synthesis and structural modification. During recent research, metal-free organic dyes show the potential to take the place of metal complex sensitizers. However, metal-free dyes show poor performance in the near-infrared region. Therefore, it is significant to develop efficient near-infrared and metal-free sensitizers for DSCs.Firstly, three organic dyes (LJ101, LJ102, and LJ103) with different π-bridges such as thiophene,3-hexylthiophene and3,4-ethyldioxythiophene were prepared and applied for the dye-sensitized solar cells. The structures of LJ dyes have been characterized by mass spectra (MS) and1H NMR. The absorption and emission spectra, electrochemical measurements and density functional theory (DFT) calculation were carried out to estimate the optical and physical properties of these dyes. Furthermore, electrochemical-impedance spectroscopy (EIS) was performed to get insight into the charge transport process in DSCs. Since the introduction of π-bridges can extend the conjugation of molecules, the absorption spectra were redshift and molar extinction coefficients were increased. However, the LUMO levels are diminished and the performances of DSCs based on LJ dyes are slightly lower than that displayed by the parent dye TH305without π-bridges. This is most possibly due to the poor electron injection efficiency from excited dyes to TiO2conduction band.Porphyrins have gained attention as sensitizers due to their absorption in500-700nm and extended conjugation in structures. Herein, three silicon-porphyrin sensitizers based on axial adsorption have been reported, coded as LJ201, LJ202and L203. The structures of molecules have been characterized by mass spectra (MS) and1H NMR. The introduction of axial ligands units can suppress molecular aggregation. Furthermore, the bulky triphenylamine units introduced to LJ203could also reduce interfacial recombination. As a result, LJ203exhibited the highest overall efficiency. Through the resonance FTIR technique, it is found that the binding mode of LJ201is unidentate, indicating the low efficiency of electron injection. Electrolyte plays an important role in electron transfer in DSCs and now the most popular and efficient electrolyte system is the I-/I3-. However, I3-has strong absorption in visible region and chemical stability problem in large-scale commercial DSCs. The use of volatile organic solvents also has negative effect on the performance of DSCs in large scale application. Therefore, the development of alternative redox couples and non-volatile electrolytes is very important.The new binary solvent-free ionic liquid electrolytes containing the S2/Sx2-redox couple and I-were employed for DSCs based on N719and TH305. The photovoltaic properties and electron transfer process in DSCs were studied. The electrolytes are nearly colourless. Their performances are attractive as the none-iodine ionic liquid electrolytes under low light intensities or1sun intensity. At last, the binary electrolytes containing the I-/quinone redox couple were applied in DSCs. This redox couple has the tendency of recombination with electrons, therefore more work has been done for further application.更多还原