【作者】 赵娟；

【导师】 靳正国；

【作者基本信息】 天津大学 ， 材料学， 2005， 硕士

【摘要】 能源与环境问题日益突出,纳米晶太阳能电池(NPC)以其工艺简单,成本低廉以及可望规模化生产等优势成为绿色能源领域的研究热点。本文综述了NPC电池及其光阳极材料的发展,研究了纳米ZnO棒晶薄膜的溶液化学法制备及其在辅助电场下的生长,并对ZnO纳米棒晶薄膜的生长机理进行了讨论。本文采用过饱和硝酸锌/氢氧化钠溶液在ZnO晶种面上制备均匀一致,取向好,长径比大的ZnO纳米棒晶薄膜;用相平衡图和羟基氧化反应讨论了无电场和电场下ZnO薄膜的沉积机理;采用了SEM、XRD、TEM、HRTEM和UV-VIS表征了薄膜的相组成、结晶形貌和透光率。提出了过饱和溶液中ZnO的结晶包括特定表面上的异质成核和随后的晶体生长两个过程;溶液化学法中ZnO纳米棒沿c轴方向层状生长;外加电场下OHˉ氧化,产生的H+增加基底附近的过饱和度,同时电场促进离子的吸附和扩散,降低成核势垒。二者均有助于ZnO纳米棒的生长。研究了基底的预处理及无电场和电场下各种溶液生长条件如前驱体溶液的浓度、沉积的温度和时间对纳米棒生长的影响。研究表明,制得的ZnO纳米棒直径约25 nm,生长1.5 h后长600~800 nm。无电场时制得的ZnO纳米棒属纤锌矿结构,而在电场下制得的主要是红锌矿结构。ZnO晶种面的织构对纳米棒的形态具有明显的影响,300~400oC热处理、急冷或低的拉膜速度或适量PEG添加的条件下制备的晶种面具有更高的晶体取向和较少的表面缺陷。从而导致生长面高的成核密度,使得ZnO纳米棒能够在垂直于基底的方向上择优生长。溶液生长条件对纳米棒的尺寸也具有显著的影响。随溶液前驱体浓度的增加,ZnO纳米棒径略微增大而棒长显著变大。对于一定浓度的前驱体溶液,纳米棒在特定温度下有最大棒长,且这一最佳温度随前驱体溶液浓度变大而升高。更多还原

【Abstract】 Increasing concerns on energy crisis and pollution problem arouse considerable attention on nanocrystalline photoelectrochemical cells (NPC) for their potentials in simple process, low cost and large scale production. In this paper, developments on NPC cells and its anode were reviewed. Solution chemical deposition of ZnO nanorod thin films without and with electrical field and the working mechanism were investigated.Equiareal ZnO naorods with high orientation and a high aspect ratio on ZnO-coated seed substrates were fabricated from the Zn(NO3)2/NaOH supersaturated solutions; the mechanisms without and with electrical field were discussed based on the phase stability diagram for solid ZnO and the oxidation of OHˉ. The phase composition, crystalline morphology and optical transmittance of ZnO nanorod thin films were analyzed by SEM, XRD, TEM, HRTEM and UV-VIS.It was proposed that two processes are required for crystallization in a supersaturated solution: heterogeneous nucleation on a specific surface and subsequent crystal growth. The prepared ZnO single crystal grows layer by layer along c-axis. The electrical field enhances ion adsorption to substrate and lowers the nucleation energy barrier by increasing charge intensity; meanwhile it produces H+ through oxidation of OHˉand increases properly the degree of solutionsupersaturation near the substrate surface. Both aspects do favor to rod growth. The factors affecting the rod growth such as pretreatment of substrates, potential, precursor concentration, deposition temperature and growth time were elucidated. The experimental results showed that the average diameter of the nanorods is ~25 nm, with a length of 600~800 nm after growing for 1.5 h. The nanorods have wurtzite structure without electrical field assistance and are primarily of zincite structure under electrical field. The texture of the ZnO seed surface has great effects on morphology of resultant nanorods. The seed surface prepared by heating at 300~400oC, fast cooling, drawing at lower speed or proper PEG adding has better orientation and few surface defects, which leads to higher density of nuclei on the seed surface and thus the preferred crystal growth of ZnO rods perpendicular onto substrates. The solution condition also plays a great role in rod size. With the Zn2+ ion concentration increasing, the average diameter of ZnO nanorods increases slightly, while the growth更多还原