【作者】 唐笑；

【导师】 钱觉时；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2008， 博士

【摘要】 染料敏化太阳能电池（Dye-sensitized Solar Cell,DSC）具有较常规太阳能电池成本更低且绿色环保的优点,是一种很有发展前途的太阳能光电转换新技术。DSC光电转换效率虽然还不够高,但由于其成本低廉,仅为单晶硅太阳能电池的1/10,可以通过大面积使用来弥补其效率低的不足。因此,非常适合于与建筑相结合使用,如建筑外墙、屋顶、门窗、玻璃幕墙等,有望成为最有发展前途的大面积供电系统。TiO₂介孔薄膜是目前DSC使用最为普遍的光电极材料,在DSC中作为染料的承载体,并起到光生电子接收体和传输体的作用,是决定DSC光电转换性能的关键组分部分。TiO₂介孔薄膜要成为产业化发展和大面积使用的DSC光电极材料,还存在以下问题:1)TiO₂薄膜的制备方法还有待改善,需要一种工艺更简单、更易于控制的制备方法;2)TiO₂薄膜光电极性能波动性有待改善;3)TiO₂薄膜光电极的光电转换效率仍然有待提高。本论文尝试采用非晶态TiO₂介孔薄膜作为DSC光电极材料来解决以上问题。采用四氢呋喃改性CTAB/水/正丁醇/环己烷反胶团微乳液法在常压、50～60℃下合成出尺寸20nm左右、高度分散的球形纳米颗粒,将其胶体前驱液直接涂膜,通过干燥、烧结,成功制备出均匀的非晶态TiO₂介孔薄膜。该制备方法由于无需控制TiO₂的晶体生长过程,因而大大降低了TiO₂纳米颗粒的合成条件;由于从TiO₂的胶体前驱液直接涂膜,在干燥和烧结过程中不会发生开裂、剥落现象,而得到由球形纳米颗粒相互连接形成的均匀TiO₂介孔薄膜,因此大大简化了薄膜的制备工艺。在相同条件下比较测试了非晶态TiO₂介孔薄膜和纳米晶锐钛矿TiO₂介孔薄膜的染料吸附量以及所组装DSC的光电转换性能指标,如短路光电流（Isc）、开路光电压（Voc）、填充因子（ff）和总光电转换效率（η）。试验结果表明,当薄膜厚度在3～16μm范围内变化时,非晶态TiO₂介孔薄膜的染料吸附量比纳米晶锐钛矿TiO₂介孔薄膜少1.18～5.76×10-8mol/cm2,该差距随薄膜厚度的增加愈加明显。但是,在染料吸附量小得多的情况下,非晶态TiO₂介孔薄膜光电极却能够产生与纳米晶锐钛矿TiO₂介孔薄膜光电极相当的Isc,并得到更高的Voc和ff,从而使得其获得较高的η。在相同条件下,非晶态TiO₂介孔薄膜光电极的最大η为5.37%,纳米晶锐钛矿TiO₂介孔薄膜光电极获得的最大η为4.69%。对比研究了非晶态TiO₂介孔薄膜和纳米晶锐钛矿TiO₂介孔薄膜的电学性质和光学性质。发现非晶态TiO₂介孔薄膜对可见光具有强散射效应,而纳米晶锐钛矿TiO₂介孔薄膜对可见光的散射较弱,这使得吸附了染料的非晶态TiO₂薄膜光电极的光利用率高于吸附了染料的纳米晶锐钛矿TiO₂薄膜光电极。此外,采用FTO导电玻璃作为与TiO₂面接触的两极,测试了TiO₂薄膜在光照下的电阻值R。发现在吸附染料的情况下,非晶态TiO₂介孔薄膜的R值比纳米晶锐钛矿TiO₂介孔薄膜的小一个数量级;在未吸附染料的情况下也得到同样的结果。说明电子在非晶态TiO₂介孔薄膜中输运的效率要高于在纳米晶锐钛矿TiO₂介孔薄膜中的输运。基于非晶态TiO₂介孔薄膜特殊的光学和电学性质,以及纳米晶锐钛矿TiO₂介孔薄膜对染料的强吸附性,将两种薄膜复合成双层结构的非晶态/纳米晶TiO₂介孔薄膜,发挥两种薄膜材料各自的优势,使其DSC的总光电转换效率η达到了6.89%,比单独由非晶态TiO₂介孔薄膜和纳米晶锐钛矿TiO₂介孔薄膜组装的DSC的总光电转换效率提高了28%左右。更多还原

【Abstract】 Dye-sensitized solar cell （DSC） has a good prospect for application of solar conversion devices because of its lower-cost than the conventional semiconductor solar cells and environment friendliness. Although the overall light-to-electricity efficiency of DSC is not high enough compared to the silicon solar cells, DSC can be used as the effective large area solar conversion device for the application in architecture, such as the external wall, the roof, the window and the curtain wall, since it is inexpensive to manufacture.TiO₂ mesoporous film, the most widely used photoelectrode material of DSC, is the key componet of DSC because it adsorbs dye and serves as both electron acceptor and transport layer. There are several problems for TiO₂ mesoporous film to realize the industrial development: （1） the fabrication method still needs to be improved with more controllable and simpler process; （2） the fluctuated efficiency of TiO₂ film photoelectrode needs to be improved; （3） the overall light-to-electricity efficiency of TiO₂ film photoelectrode needs to be enhanced. An amorphous TiO₂ mesoporous film is used as photoelectrode of DSC to resolve these problems.The spherical TiO₂ particles with an average size of 20nm were synthesized by the Tetrahydrofuran modified reverse microemulsion method under atmospheric pressure and the temperature of 50⁶0℃. The resulting colloid was coated straight on the FTO conducting glass, fllowing by drying and sintering processes, to form an amorphous TiO₂ film with homogeneous mesoporous inner structure of interconnected spherical particles. The method makes the synthesis conditions for TiO₂ nano-particles much lower than for the TiO₂ nanocrystallines attributing to no demand of crystallization and growth for amorphous TiO₂. The method also makes preparing process much simpler owing to supporting to coat the colloid straight on the substrate to form a homogeneous mesoporous TiO₂ film.Under the same conditions, the dye-adsorption amount and performances, such as short circuit photocurrent （Isc）, open circuit photovoltage （Voc）, fill factor （ff） and the overall light-to-electricity efficiency （η）, of the amorphous TiO₂ mesoporous film were measured and compared with those of the anatase nanocrystalline mesoporous film prepared by P25. The experimental results shows that the dye-adsorption amounts of the amorphous TiO₂ film are 1.18～5.76×10-8mol/cm2 less than those of the anatase nanocrystalline film when the film thicknesses vary from 3μm to 16μm. However, with much less dye-adsorption amout, the amorphous TiO₂ film photoelectrode generates equivalent Isc, higher Voc and ff comparing with the anatase nanocrystalline film photoelectrod, hence higherη. The maximum ofηis 5.37% for the amorphous TiO₂ film based DSC and 4.69% for the anatase nanocrystalline film based DSC.The electrical and optical properties of the amorphous TiO₂ mesoporous film were measured and compared with those of the anatase nanocrystalline mesoporous film prepared by P25. It was found that the amorphous TiO₂ mesoporous film had high light scattering ability, which enhanced the light utilization of dye molecules in the film, while CM-TiO₂ film had poor light scattering. In addition, the resistances of TiO₂ films were tested by using two sheets of FTO conducting glass serving as electrical contact material with TiO₂ film, which allowed the irradiation of light and accorded with the practical electrical contact situation of TiO₂ film with FTO conducting glass substrate in DSC. Under irradiation, the resistance of dye-loaded or -unloaded amorphous TiO₂ film is about one order of magnitude lower than that of anatase nanocrystalline film. It indicates that the photo-electrons transport through AM-TiO₂ film more efficiently than it does through CM-TiO₂ film.Based on the especial electrical and optical properties of the amorphous TiO₂ mesoporous film and the high ability of adsorbing dye of the anatase nanocrystalline mesoporous film, the DSC based on the composite TiO₂ film with the double layered structure of the two kinds of TiO₂ films obtainedηof 6.89%, which was 28% higher than that obtained neither by the DSC based on the pure amorphous TiO₂ film or the DSC based on the anatase nanocrystalline film.更多还原