【作者】 詹卫伸；

【导师】 潘石；

【作者基本信息】 大连理工大学 ， 光学， 2010， 博士

【摘要】 自从20年前发明染料敏化太阳能电池(DSSC)以来,研究人员一直在寻找性能优良的光敏剂用于DSSC,以期改善DSSC的光电性能,提高光电能量转换效率。为了降低DSSC的成本,最近几年研究者们开始关注使用非金属有机光敏剂染料来代替贵金属配合物。经过多年的探索,目前已经认识到适合于高效率DSSC的非金属有机光敏剂分子应该具有“电子给体—共轭桥—电子受体(D—π—A)”型分子结构。目前已经合成了多种D—π—A型非金属有机光敏剂,并用于敏化DSSC,使DSSC光电能量转换效率逐步提高。但目前DSSC的光电能量转换效率仍然不到10%,还远没有达到大规模工业化生产的地步。主要问题是：染料分子的吸收光谱位于紫外—可见光光谱的短波区,不能充分利用太阳能；由染料激发态向TiO2电极的电荷转移效率较低。合成吸收光谱明显红移的有机染料光敏剂,是目前DSSC研究的迫切任务。由于有机分子结构的多样性,通过分子修饰有可能调整分子的光物理和电化学特性,使之适合于敏化DSSC。在尝试合成染料分子前,如果能够在理论上通过对分子进行修饰并预言其性能而设计新分子,将是非常经济和快捷的方法。本文通过对目前合成的几类染料分子的DFT/TDDFT模拟计算,并与实验结果进行比较,寻找影响DSSC光电性能和光电能量转换效率的光敏剂分子的关键指标；以这些指标为依据,对目前已经合成的两种染料分子进行修饰,从中挑选出性能优良的敏化DSSC的有机分子,为进一步合成高效率非金属有机染料分子提供参考。通过对二氢吲哚类、多烯类和呋喃类染料分子的DFT/TDDFT模拟计算,并与实验结果比较发现,染料分子的HOMO和LUMO能级,吸收光谱以及摩尔吸光系数是决定DSSC性能的关键因素。通过增加共轭桥(次甲基链、噻吩环、呋喃环)的DFT/TDDFT计算表明,共轭桥的增长,确实能引起分子吸收光谱的红移。但计算结果也表明,共轭桥不宜太长,以1个单元为合适,不宜超过2个单元。通过在染料D5分子骨架上的不同部位引入不同的给电子基(-OH,-NH2,-OCH3)和受电子基(-CF3,-F,-CN),设计54种D5同类物分子。通过DFT/TDDFT模拟计算这些分子的几何结构、吸收光谱,以及能级结构,从中筛选出两种分子,由其敏化的DSSC的性能可能优于D5分子。同样,对含呋喃染料F1的分子修饰也筛选出两种分子的性能可能优于染料F1分子。这为进一步合成高效的DSSC光敏剂提供了理论参考。更多还原

【Abstract】 Since dye sensitized solar cells (DSSCs) were invented twenty years ago, researchers have always sought a good photosensitizer for DSSC. in order to improve the electro-optical properties of DSSC and enhance electro-optical energy conversion efficiency. To reduce the cost of DSSC. researchers have begun to pay close attention to the use of non-metallic organic photosensitizer dye as replacement of precious metal complexes in recent years. In this stage, researchers have recognized that the non-metallic organic photosensitizer molecules suitable for efficient DSSC should have the molecular structure of "electron donor-conjugated bridges-electron acceptor (D-π-A)".At present, many kinds of D-π-A non-metallic organic photosensitizer have been synthesized and have been used for sensitized DSSC, in order to gradually enhance the electro-optical energy conversion efficiency of DSSC. However, the electro-optical energy conversion efficiency of DSSC is still less than 10% now, which falls behind large-scale industrial production. There are several facets to this question:on the one hand the adsorption spectra of dye molecules at the short-wave area of ultra-violet visible spectra fail to make full use of solar energy; on the other hand the charge transfer efficiency from the excited state of dye to TiO2 electrode is low. The synthesis of organic dye photosensitizer with significant red-shift adsorption spectra is the urgent task of current research on DSSC.Due to the diversity of organic molecular structure, the photo-physical and electro-chemical characteristics of molecules may be adjusted to be suitable for DSSC through molecular modification. It will be a very economic and fast method to design new molecules by theoretically modifying molecules and predicting their properties before trying to synthesizing dye molecules. By DFT/TDDFT simulation calculation for currently synthesized dye molecules and comparison with experimental results, this paper sought the key indicators of the photosensitizer molecules that influence on the electro-optical properties and electro-optical energy conversion efficiency of DSSC; based on these indicators, the currently synthesized two kinds of dye molecules were modified, in order to select the organic molecules with good properties for DSSC, which provides reference for the further synthesis of efficient non-metallic organic dye molecules.By DFT/TDDFT simulation calculation for dihydroindole, polyene and furan dye molecules and comparison with experimental results, one found that the HOMO and LUMO energy levels of dye molecules, adsorption spectrum and molar absorption coefficient should be the key factors that determine the properties of DSSC.The DFT/TDDFT calculation for the increasement of conjugated bridges (methylidyne chain, thiophene ring and furan ring) show that the increase in conjugated bridges can cause the red-shift of molecular adsorption spectrum indeed. However, the calculation results also show that the conjugated bridges should not be too long, i.e. one unit should be enough, and two units should not be exceeded.Through the introduction of different electron-donating groups (-OH,-NH2,-OCH3) and electron-accepting groups (-CF3,-F,-CN) into different parts on the skeleton of dye D5 molecules.54 kinds of D5 analogue molecules were designed. By DFT/TDDFT simulation calculation for geometric structure, adsorption spectrum and energy level structure of these molecules, two kinds of molecules superior to D5 molecules in properties were sieved out. In the same way, by molecular modification for furan-laden dye F1, another two kinds of molecules superior to dye F1 molecules in properties were sieved out. This provides theoretical reference for the further synthesis of efficient DSSC photosensitizer.更多还原