【作者】 孟凡宁；

【导师】 王同华；

【作者基本信息】 大连理工大学 ， 化学工艺， 2012， 硕士

【摘要】 染料敏化太阳能电池(Dye-sensitized solar cells,简称DSSC)是根据光生伏特原理,将太阳能直接转化成电能的一种半导体光电器件。与传统的硅太阳能电池相比较,其主要的优点是成本低廉、制作工艺简单和性能稳定。传统的DSSC对电极(counter electrode, CE)采用的是贵金属Pt作为催化剂,导电玻璃作为基底。近年来,为了降低DSSC的制作成本,炭材料在DSSC对电极的应用越来越受到关注。大多数文献中报导将合成并炭化后的催化剂涂覆在导电玻璃基底表面制备炭对电极。这种工艺制备的对电极催化层导电性和催化活性都比较差,同时导致催化层附着性问题。本论文针对炭对电极制备中存在的问题,设计一种新型的结构一体化的炭基对电极,并进行了系统地研究。本论文采用自制的煤基炭CE同时代替FTO导电玻璃和Pt催化层组装DSSC进行了性能表征和测试。煤基炭CE具有无定形碳的结构,表现出良好的导电性和对I3-还原反应良好的催化活性,其中气煤基炭CE组装的DSSC经过封装测试其光电转化效率达到了相同实验条件下传统Pt电极的89%,表现出良好的光电性能；经过浸渍处理的气煤基炭CE,在不改变其效率的前提下,结构得到了改良,形成了底层致密表面多孔的结构；同时还对气煤基炭CE进行了表面修饰,结果显示表面修饰后的光电性能得到大幅度提高,其光电转化效率达到了7.16%与传统Pt电极的效率(7.21%)相当,超过了石墨电极电池效率30%。本论文自制的纯炭CE表面的有序介孔炭(ordered mesoporous carbon, OMC)催化层具有高度有序、紧密排列的碳骨架结构,DSSC电解质中的I3-和I-在有机电解液中尺寸大约为0.5和0.22nm,明显小于介孔的孔径(6-8nm),这有利于I3-快速进入介孔孔内发生还原反应,同时生成的I-也能快速的从孔内扩散到电解液中,揭示了具有OMC催化层的纯炭CE具有更高光电性能的原因。同时考察了OMC催化层不同炭化温度对纯炭CE光电性能的影响,不同炭化温度主要影响OMC催化层的碳骨架结构和催化层的比表面积,OMC催化层800℃炭化时具有最大的比表面积832.46m2/g,具有最好的光电性能。其电池效率达到了8.73%,稍高于传统Pt电极的电池效率(8.64%)。考察了不同介孔结构对纯炭CE性能的影响,与WMC催化层比较,OMC催化层表面高度有序的介孔结构能为有利于I3-扩散进入介孔内发生还原反应,同时有利于生成的I-从孔中向外扩散,OMC催化层纯炭CE具有更好的电池效率。与此同时在基底中分别掺杂了石墨和炭黑颗粒,考察了不同基底对纯炭CE光电性能的影响,当对电极催化活性欠佳时,提高对电极导电性可以在一定程度上提高电池效率；当对电极表面催化层对于I3-还原反应能提供良好催化活性时,对电极导电性改善不能进一步提高电池的效率纯炭CE和煤基炭CE表面含有一定数量和比例的含氧官能团,即-C-OH、O=C-O-和-COOH。当两种对电极表面含氧官能团数量发生变化时,会引起对电极的光电性能发生不同程度的变化,电子在对电极/电解质界面的传递过程中阻力发生变化,电池效率也会随之发生变化。更多还原

【Abstract】 Dye-sensitized solar cell (DSSC) is a semiconductor optoelectronic device, which is based on photo-volts principle. Thus, solar energy can directly convert into electrical energy by DSSC. Compared with traditional silicon solar cells, the main advantages of DSSC are low cost, simply manufacturing process and stable performance. For the conventional DSSC counter electrode (CE), transparent conductive glass is used as a substrate and Pt is the most common used as catalyst. Recently, carbon materials attract more and more attention as counter electrodes in order to lower the cost of DSSC. According to previous studies, carbon counter electrodes (CE) were prepared by simply coating of synthesized catalyst particles on the substrate. The conductivity and catalytic activity of carbon counter electrodes in such a configuration is low, and the poor catalytic activity is usually resulted. Moreover, the poor adhesion between the catalyst layer and the substrate will cause many difficulties in the following cell assembly process. Herein, a novel carbon-based CE with integrated structure has been proposed and developed; and the performance of this CE was investigated systematically.The self-made coal-based carbon CEs were used to instead both conductive glass substrate and Pt catalyst to assembly DSSC. The amorphous coal-based carbon CE exhibits high electrical conductivity and excellent catalytic activity toward the I3-reduction reaction. The gas coal-based carbon CE shows good photovoltaic performance with the cell efficiency up to89%of the conventional Pt/FTO electrode. The coal based carbon CE after impregnated demonstrates an integrated structure with a porous top surface and a dense bottom. The solar cell with surface modified coal-based carbon CE shows high solar-to-electricity conversion efficiency (η) of7.16%, which is30%higher than that of the cell with graphite electrode, comparable to that of the cell with Pt electrode (7.21%).The self-made pure carbon CE was also modified with an ordered mesoporous carbon (OMC) catalytic layer. The OMC layer shows a highly ordered, closely packed hexagonal tunnel structure. The pore width of OMC is6-8nm, which is much larger than the size of I3-and I-in the organic electrolyte (0.50nm and0.22nm, respectively). It benefits for I3-quickly accessing to active sites in the pores where reduction reaction occur, meanwhile, I-generated can quickly spread from the pore to the electrolytic fluid. It reveals why OMC catalyst layer of pure carbon CE has a higher optical photovoltaic performance. The influence of carbonization temperature of OMC catalyst layer on the optical and electrical properties of pure carbon CE was investigated. The carbonization temperature affects mesostructure and the specific surface area mainly; the OMC catalyst layer carbonized at800℃has the largest specific surface area (832.46m2/g), and displays the best photovoltaic performance also. The cell efficiency reached8.73%, slightly higher than the conventional Pt electrode cell efficiency (8.64%). The effect of the different mesoporous structures on performance of pure carbon CE was also investigated. Compared to wormlike mesoporous carbon (WMC) catalytic layer, highly ordered mesoporous structure is more benefit to I3-, and I-diffusion, thus the pure carbon CE with OMC catalytic layer has a better cell efficiency. The effect of substrate composite on the conductivity and cell performance was investigated. One can further lower the sheet resistance of substrate by using graphite and carbon black as conductive additives. When the catalytic activity of CE is poor, one can increase the cell efficiency to a certain extent by increasing the electrode conductivity; however, when the CE can provide a good catalytic activity for the I3-reduction, the improvement in the electrode conductivity have less influence on the cell efficiency.The influence of surface chemistry on the cell performance was discussed. Both pure carbon CE and coal-based carbon CE contain certain number and proportion of oxygen-containing functional surface groups, i.e.,-C-OH, O=CO-, and-COOH. Changing surface property can cause varying of the photovoltaic properties of the electrodes to some extent, the electron transfer process at the interface of counter electrode/electrolyte, thus resulting in the change of cell efficiency further.更多还原