【作者】 石德晖；

【导师】 周艺；

【作者基本信息】 长沙理工大学 ， 物理化学， 2010， 硕士

【摘要】 染料敏化太阳能电池（Dye Sensitized Solar Cell，简称DSSC）由瑞士洛桑高等理工学院Gretzel教授于1991年率先制备，立即受到国际上广泛的关注和重视。之后各国科研人员对其进行大量的研究并取得了一定的进展，但仍存在许多尚需解决的问题，如其核心部件TiO₂纳米晶膜的光电转换性能有待提高、染料急需低成本化、开发高效电解质与固态电解质、如何实现电池大面积化以及电池结构的优化等。本文采用改进的溶胶-凝胶制备工艺以及利用聚苯乙烯作为造孔剂制备Gd、N共掺杂多孔TiO₂纳米薄膜，分析了薄膜中孔隙、粒径大小等对薄膜性能的影响；根据第一原理研究轨道有序态及其对光电性能的影响，定性和定量分析TiO₂的能带变化与掺杂Gd/N等物质的关系。研究结果表明：溶胶-凝胶法所得薄膜在500℃温度下煅烧得到的TiO₂为锐钛矿晶型，颗粒的大小约为20nm。膜的表面出现较多的孔隙，没有团聚和裂痕。以此薄膜组装了DSSC，通过对其电池的I-V测试，TiO₂薄膜厚度约10μm时，其光电池的性能最好，其开路电压为0.382v，短路电流为0.332mA。TiO₂结构的多孔隙性保证了较多染料的吸附，进而增强了捕获太阳光的能力，薄膜的合适的厚度有利于使染料分子及电解质充分地吸附到纳米TiO₂中，有利于载流子的传输和转移，抑制复合与暗电流。以聚苯乙烯（PS）微球为造孔剂，结合溶胶-凝胶法制备了具有良好光电性能的锐钛矿多孔TiO₂薄膜电极。其中PS微球乳液为7%时，TiO₂薄膜电极表面分布着较多孔径均匀的圆形小孔，其光电转换效率效果最优，短路电流Isc为0.4979mA／cm²，开路电压Voc为0.6696V，填充因子FF为38.15％，比没有造孔剂时效果有大幅提高。而通过Gd、N共掺杂制备的多孔电极最好的效果，在掺杂Gd为0.5%，掺杂N为0.3%。时候，效果达到最好，其开路电压为0.649v。短路电流为0.713mA／cm²，相对没有掺杂的多孔膜电极其效率提高51.47%。采用密度泛函理论的平面波超软赝势方法研究了锐钛矿相及Gd、N共掺杂TiO₂的基态几何、电子结构，计算得到TiO₂的晶格常数与实验结果的偏差很小；掺杂能级的形成主要是掺杂Gd、N的4f轨道的贡献。掺杂Gd\N后，不仅使TiO₂的吸收带产生红移，且增强了TiO₂在紫外区的光吸收，因此Gd\N型的共掺杂能使TiO₂的禁带变窄，光电性能得到提高。更多还原

【Abstract】 Dye sensitized solar cells （DSSC） have attracted great attention as the significant progress made by Gr?tzel and co-workers in the 1990s. Though investigations into the various factors influencing the photovoltaic efficiency in this novel approach have recently been intensified, there is still many problems for the optimization of the DSSC components, i.e., the oxide semiconductor, the sensitizer, the electrolyte, large area cells and the structure of DSSC.In this paper, porous TiO₂ films co-doped with Gd and N were fabricated by sol-gel method using polystyrene（PS） as pore-forming agent. The influence of the porosity and the particle size to the photoelectric properties of TiO₂ films were investigated. The relationship between the energy band of TiO₂ and dopant of Gd/N were studied by first-principles.The results indicated that anatase TiO₂ nanoparticles were the main structural components in TiO₂ films which calcined at 500℃for 2h. And the average grain size of anatase TiO₂ was found to be about 20 nm. The porous TiO₂ films with little agglomeration and flaw were used to fabricated DSSC. The I-V test show that the photoelectric properties of TiO₂ film was the best when the thickness was about 10μm, which have a short circuit current of 0.332mA/cm², an open circuit voltage of 0.382V. This is because TiO₂ film with high porosity could absorb more dye which is beneficial to enhance the photoelectric properties of TiO₂ film, and suitable thickness of TiO₂ film is in favor of transmission and transfer of carrier, all of these could enhance the photoelectric properties of TiO₂ film electrodes.And the porous TiO₂ films fabricated by sol-gel method using PS as pore-forming agent were also composed by anatase TiO₂ nanoparticles. The influence of polystyrene microspheres （PS） mass ratio to the morphology and photoelectric property of the films were investigated. The results showed that when the PS mass ratio of 7.0%, the TiO₂ thin film electrods appeared with high porosity, uniform pore size and high photoelectric property. Under simulated solar illumination, a short circuit current of 0.4979 mA/cm², an open circuit voltage of 0.6696 V and a fill factor of 38.15% were attained, which were better than the performances of TiO₂ films without pore-forming agent. And the photoelectric properties of porous TiO₂ films co-doped with 0.5% Gd and 0.3% N was the best, which had a short circuit current of 0.713 mA/cm², an open circuit voltage of 0.649 V, whose efficient was improved about 51.47% to porous TiO₂ electrode.The ground state structures and electronic properties of anatase TiO₂ co-doped with Gd and N were calculated by using first principles method which base on plane-wave pseudopotential method. The lattice constant of the samples is in good agreement with the experimental value, and the formation of doped energy-band was main based on contribution of N and 4f-orbitals of Gd. TiO₂ co-doped with Gd and N not only have a red shift, but also enhance the light absorption in the ultraviolet region, hence the TiO₂ co-doped with Gd and N could increased the electronic propertie.更多还原