【作者】 陈云霞；

【导师】 赵修建；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2007， 博士

【摘要】 敏化TiO₂纳晶太阳能电池是目前纳米技术和光电转换材料研究领域的热点之一，在国外，M．Gr（?）tzel课题组已经通过了染料敏化TiO₂纳晶太阳能电池（DSSC）的中试，国内外研究者对于DSSC的进一步产业化均抱持着乐观的态度。但是在实际应用中，还存在着染料降解，染料价格昂贵，电池稳定性等问题。基于目前国内外敏化纳晶太阳能电池的发展状况，本论文创新性地提出了CuInS₂纳米粒子敏化TiO₂纳晶电池。结合已经成熟的制备薄膜和纳米粉体的技术，本论文从以下几个方面进行了研究：（1）利用成熟的溶胶工艺制备了致密的锐钛矿TiO₂纳米薄膜以及M_xO_y-TiO₂(M=In³⁺，Al³⁺，Zn²⁺，Zr⁴⁺，Cu²⁺)复合纳米薄膜，着重于In₂O₃-TiO₂复合薄膜的分析和表征；结果表明：M_xO_y-TiO₂复合薄膜中，随着M离子添加量的增大，锐钛矿TiO₂平均晶粒尺寸逐渐减小。In³⁺主要以In₂O₃晶体的形式存在，薄膜光学间接禁带宽度增大，且导电性能提高、载流子浓度和载流子迁移率均增大。其它几种离子复合的TiO₂薄膜中，各种离子以无定形氧化物存在，随着各离子含量的增加，Al³⁺、Zr⁴⁺复合TiO₂薄膜光学间接禁带宽度增大，Zn²⁺复合TiO₂薄膜光学间接禁带宽度没有明显变化，而CU²⁺复合TiO₂薄膜的光学禁带宽度则减小。（2）低级有机碱作为模板剂，120℃胶溶得到稳定的TiO₂蓝白色透明溶胶。该溶胶中存在大量层状结构的含Ti复合物。不同水热处理温度和时间条件下，分别制备了具有新颖结构的方块状锐钛矿纳米阵列及纳米棒。该均一的、单分散的、边长～13nm的锐钛矿TiO₂纳米方块阵列取向一致，类似于“准单晶”结构。制备的纳米棒长径比为3～4。由于模板剂分子的选择性吸附，这些纳米棒与纳米方块相比，径向方向略微长大，而沿着b轴方向拉长成边缘规整的纳米棒状粒子。随着有机碱碳链的增长，水热产物更趋向于形成棒状纳米粒子。（3）通过pH=1.5的HNO₃酸性条件下胶溶与水热处理结合的方法制备了8.8～16.6nm大小的TiO₂纳米粉体和M_xO_y-TiO₂(M=In³⁺，Al³⁺，Zn²⁺，Zr⁴⁺)复合纳米粉体。M_xO_y-TiO₂复合粉体中锐钛矿TiO₂平均晶粒尺寸均小于相同条件下处理的TiO₂纳米粉体。M离子的加入，在复合体系中形成了各自的氧化物晶体，此外，In³⁺复合的TiO₂体系中生成了常规条件下1000℃高温反应才有的In₂TiO₅晶体；Zr⁴⁺复合的TiO₂体系中形成了ZrTiO₄晶体。（4）采用简单湿化学法制备CuInS₂和CdS光吸收层材料。所制备的100～200nm厚黄铜矿结构CIS薄膜的吸收系数α均在10⁵cm^-1数量级，薄膜的近似光学禁带宽度E_gd为1.28～1.62eV。前驱体溶液中Cu／In比例固定不变，薄膜的α随着S含量的增加而增大，E_gd随着S含量的增加而减小；S比例保持不变时，薄膜的α随着In含量的增加而增大，E_gd则随着In含量的增加而减小。CdS薄膜中以立方晶系的CdS晶相为主，晶粒平均尺寸为24nm。薄膜近似光学禁带宽度为2.37～2.38eV。（5）将上述所制备的材料按照“三明治”结构组装成电池进行开路电压和短路电流的测试，并与商业P25粉体制备的电极性能做比较。测试结果表明：天然染料敏化的P25膜电极在10μm厚时获得最大光电转换效率。一定厚度的无机半导体CIS敏化P25电池中，CIS吸收层在较薄的情况下获得一定的光电转换效率。与CdS敏化电池相比，以CIS敏化的TiO₂电池开路电压和短路电流值最小，但填充因子最大。复合电极材料中，In³⁺复合TiO₂纳米电极主晶相为In₂TiO₅，导致电池Jsc和Voc均很小；Al³⁺复合TiO₂纳米电极中Al以其氧化物的无定形形式存在，电池的开路电压相对较大。Zn²⁺复合TiO₂纳米电极中存在ZnO次晶相。其中，以ZnO复合的电极短路电流密度最大。更多还原

【Abstract】 TiO₂ nanocrystalline solar cell is one of hotspots in the field of materials for photo-electric energy conversion and nanotechnology. Abroad, the research group of M. Gratzel has made a rapid progress in the pilotscale experiment of dye-sensitized TiO₂ nanocrystalline solar cells （DSSCs）. Many researchers are optimistic in the industrialization of DSSCs. Even now, several problems, such as dye degradation, high price of dye, and stability of cells, still lie in practical applications. Based on the development of DSSCs in the world, this dissertation presents a new type of CuInS₂ nanocrystalline sensitized TiO₂ solar cell. Combined with mature technologies of preparing thin films and nanoparticals, the main studies of this dissertation are listed as following:（1）Compact anatase TiO₂ nanacrystalline thin films and M_xO_y-TiO₂(M=In³⁺, Al³⁺, Zn²⁺, Zr⁴⁺, Cu²⁺) composite thin films were prepared and In₂O₃-TiO₂ composite thin film was maily studied based on the mature technology of sol-gel. In the case of M_xO_y-TiO₂ composite thin films, with the increment of M ions, the mean grain size of anatase TiO₂ decreases. In₂O₃ crystals are found to exist in the as-prepared In₂O₃-TiO₂ composite films, which resuls in the increase of optical indirect bandgap (E_gi), conductivity, concentration and mobility of carriers. In the other cases of Al³⁺, Zn²⁺, Zr⁴⁺, Cu²⁺-incorporated TiO₂ films, these ions are considered to be in existence of amorphous oxides. E_gi of the as-prepared Al³⁺, Zr⁴⁺ incorporated TiO₂ film increases. On the contrary, E_gi of Cu²⁺-incorporated TiO₂ film decreases. And the presence of Zn²⁺ can’t influence E_gi obviously.（2）Stable blue-white transparent TiO₂ sols were fabricated at 120℃and short-carbon chain organic alkali played a role of a structural template. Large quantities of layered Ti-compound were proved to be in the as-prepared TiO₂ sols. A novel anatase TiO₂ nanosquares array and regular nanorods were repectively synthesized at different autoclaved temperatures for different hours. The results reveal that the as-prepared anatase nanosquares with the edge length of～13nm are mono-dispersed, uniform, and quasi-singe crystalline. Aspect ratio of the as-fabricated anatase nanorods is 3～4. Compared with the nanosquares, the nanorods grow up slightly in radial direction and elongate into rods along b-axial direction due to the selectively adsorption of template molecules. With the increase of carbon chain of the organic alkali templates, the as-prepared nanoparticles are inclined to the formation of rod-like nanoparticles.（3）TiO₂ nanoparticles with the mean grain size of 8.8～16.6nm and M_xO_y-TiO₂(M=In³⁺, Al³⁺, Zn²⁺, Zr⁴⁺) composite nanopowders were fabricated at pH=1.5 by peptizing and hydrothermal treatment. In the case of M_xO_y-TiO₂ composite nanopowders, anatase TiO₂ is the main crystal phase, and M_xO_y exists as a minor phase. The growth of anatase TiO₂ nanocrystals is suppressed due to the presence of M_xO_y. It is noted that In₂TiO₅ is formed in the In₂O₃-TiO₂ composite nanopowders. Generally, In₂TiO₅ occurs in the systems which must be heat-treated at 1000℃. In the case of Zr-incorporated TiO₂ composite powders, ZrTiO₄ is formed.（4）Wet-chemical methods were employed to fabricate CuInS₂ （CIS） and CdS light -absorbed layers. The as-fabricated CIS thin films with the thickness of 100～200nm have high absorption coefficient （α） of 10⁵cm^-1, and narrow direct bandgaps (E_gi) of 1.28～1.62eV. Keeping Cu/In ratio constant in the precursor solutions, the absorption coefficient increases and E_gi decreases with the increment of S; In addition, the absorption coefficient increases and E_gi decreases with the addition of In³⁺ when keeping S content constant. Cubic CdS crystal with the mean grain size of～24nm is the main phase in the CdS thin films fabricated by CBD method. And the optical bandgap of the as-prepared CdS thin film is 2.37～2.38eV.（5）Solar cells were assembled according to "sandwich" structure using the materials refered above and characterized with open-circuit voltage (V_oc) and short-circuit current density (J_sc). The testing results show that natural dye-sensitized P25 nanocrystailine solar cell with the thickness of 10μm has the max energy conversion efficiency （η）. In the case of CIS semiconductor-sensitized P25 solar cells, the photovoltaic efficiency of cells with thinner sensitizer is a little higher than that of cells with thicker sensitizer when P25 films are kept constant. Among all of the as-fabricated solar cells, CIS-sensitized solar cell has the minimum Voc and Jsc, but the filling factor （FF） of it is the biggest. M_xO_y-TiO₂ composite nanopowders were also used to fabricate photoanodes of DSSC by "doctor blade" approach. The solar cell based on In₂O₃-TiO₂ composite anode has bad photovoltaic properties because of the formation of In₂TiO₅. The solar cells with amorphous Al₂O₃-TiO₂ or ZrO₂-TiO₂ composite anode have relatively higher open-circuit voltage. In addition, The solar cell with ZnO-TiO₂ composite anode has relatively higher short-circuit current density.更多还原