电化学法制备染料敏化太阳能电池中的纳米结构聚苯胺薄膜对电极

电化学法制备染料敏化太阳能电池中的纳米结构聚苯胺薄膜对电极 附件2 论文中英文摘要格式 作者姓名:图布新 论文题目:电化学法制备染料敏化太阳能电池中的纳米结构聚苯胺薄膜对电极 7年9月师从于内蒙古大学 张作者简介:图布新，男，1982年4月出生，200 君 副教授，于2010年7月获 硕士 学位。 中 文 摘 要 目前全球环境污染及能源紧缺己成为人类面临的两大问题。我国人口多，人均能源资源占有量不到世界平均水平的一半。能源、资源相对不足已成为制约经济、社会可持续发展的一个重要因素。发展绿色能源与可再生能源，是解决能源问题和减少环境污染的有效手段。 现有的能源体系，小部分来源于直接利用太阳能、风能和水能，大部分来源于二次能源――煤，石油、天然气以及核能等。其中，煤作为传统火力发电厂的主燃料，石油、天然气作为城市交通运输的主燃料，在能源供应方面都发挥着巨大的作用，但由于化石类能源利用所带来的环境污染以及储量有限，开发环境友好的，能多次利用的新能源已成为全世界有识之士所关注的课题。 从能源长久与环境友好的角度考虑，综合利用太阳能是最安全，最环保又最长远的方法之一。当前太阳能作为一种无污染的重要自然能源越来越受到世人的重视。在我国，目前大约仍有一亿人口未能解决可靠供电问题，主要分布在内蒙古、新疆、青海、甘肃等省区，其中内蒙古是重点地域，由于牧区地域宽广，牧民居住相对分散，广大牧业区及部分农区急需电能，发展农牧区新能源是适应商品经济和提高人民生活水平的物质基础，无电是阻碍其发展的重要原因之一，解决供电问题，对于加强民族团结，改善当地生活水平，发展地方经济，稳定社会，巩固边防都有着十分重要的意义。 为此，进行大面积太阳能电池方面的基础研究，尤其是研究光电转化效率较高、薄轻、易铺设的太阳能电池的电极部分具有重要的理论和实际意义。凭借内蒙古地域广阔、日照时间长和光照强度大等有利自然条件以及稀土资源丰富的资源优势，在内蒙开展符合当地特点的相关研究，极有希望使得这一地区成为我国未来的超大型太阳能洁净能源供应基地。进行符合本地区特点的染料敏化柔性太阳能电池的电极方面的基础研究显得尤为必要。 与传统的全固型半导体光电池不同，染料敏化太阳能电池(DSSC)是一种新型的光电化学电池。通常，染料敏化太阳能电池由带有染料的纳米晶二氧化钛光电极、对电极和电解质组成。其原理是利用染料使得光电化学电池的无机半导体电极对可见光变得敏感。阳极由覆盖有一层二氧化钛纳米晶粒的薄膜的透明导电玻璃组成，电子传导通过纳米尺寸相互连接的颗粒所组成的网状结构来进行。膜的厚度从几百纳米到十几微米不等。钌系染料分子通过功能基团(羧基或磷酸基) 化学吸附于半导体的表面，孔隙由含有氧化还原对的电解质填满，涂有光触媒铂的导电玻璃作为对电极，与负载组成回路。其总的机理是:光被染料吸收，导致电子迅速注入半导体的导带，吸附的染料通过存在于电解质相的三合碘离子的电子传递得到再生。这种染料敏化电池中最具前途的是基于吸附有钌系染料的浸于液态电解质中的纳米晶粒的二氧化钛来实现的，其中纳晶二氧化钛和染料的紧密接触增进了电荷传递，并扩大了光吸收界面。 对电极是染料敏化太阳能电池中的重要组成部分，它主要进行电解质中氧化还电对的再 生，对电池的性能和成本的降低具有重要意义，铂因其优良的性能被广泛用于染料敏化太阳能电池中作为对电极材料，但铂材料稀少，价格昂贵，人们开展了铂的替代物的研究。如石墨、碳黑、碳纳米管及导电聚合物等。其中，聚苯胺(PANI)是广为人知的一类导电聚合物，具有低成本，制备简单，优良的环境稳定性，使用稳定和还原催化性能，应用于二次电池，传感器，电容器等电器件领域。聚苯胺材料的合成方法主要有化学氧化聚合法和电化学合成法。化学氧化聚合法主要是在溶液中通过氧化剂引发使单体聚合为导电聚合物。电化学方法制备聚苯胺是，一般在酸性条件下在苯胺单体溶液里，在电化学电池系统(三电极体系)下，对体系施加电压或者采用电流驱动反应，使苯胺单体在电池得阳极表面发生氧化聚合反应，最后在粘附于阳极表面形成聚苯胺。比起化学氧化聚合法，电化学合成方法在常温，常压条件下进行，具有操作简单、成本低、反应时间短、制备出的聚苯胺纯度高、聚合反应过程易控制，无需进行反应副产品的进一步清除处理等优点。 本论文提出了一种运用简单电化学方法制备染料敏化太阳能电池中的聚苯胺对电极的方法，并成功用作染料敏化太阳能电池的对电极，并在此基础上建立了电化学原位聚合生长聚苯胺的理论模型。 在室温条件下，运用电化学循环伏安技术在掺杂氟的二氧化锡(FTO)玻璃导电面原位聚合制备出不同厚度的聚苯胺薄膜。 通过对不同循环伏安扫描段数的聚苯胺对电极的表面的扫描电镜和原子力显微镜观测，以及对电极截面的扫描电镜观测来研究电极表面聚苯胺的微观形貌和厚度。研究发现:聚苯胺在电化学方法下制备时，首先在FTO玻璃导电层表面形成球形纳米结构的聚苯胺薄层，之后随着扫描次数的增加，球形结构的聚苯胺层逐渐增加并更加致密，并有线状结构的聚苯胺逐渐形成，进而线状结构的聚苯胺形成占据主导地位，使得电极表面被线状结构的聚苯胺所铺满，而且线状结构的聚苯胺增长迅速，形成了具有多孔网状结构的聚苯胺疏松层。另外，FTO导电层布满200-300nm左右的长条状的掺氟二氧化锡颗粒，颗粒之间相互连接，导电层的厚度平均为700nm左右。球形结构的聚苯胺平均粒径在100nm以内，电化学法沉积的铂纳米颗粒的粒径分布在30-50nm之间，它们具有在原子力显微镜下很容易分辨的不同微观形貌和粒径。 本论文建立了电化学生长的聚苯胺薄膜理论模型。研究显示了电化学循环伏安法制备的翠绿亚胺式聚苯胺在FTO玻璃导电面生长的过程:连续的苯环和氨基组成的聚合链在FTO玻璃表面缠绕形成聚苯胺纳米颗粒。聚苯胺的导电性能比金属差。刚开始，纳米颗粒形状的聚苯胺在FTO玻璃的金属氧化物表面较容易形成，获得低空隙率的紧密的纳米颗粒聚苯胺层。然后纳米颗粒聚苯胺层导电性能较差的缘故逐步出现和铺满线状结构的聚苯胺。13扫描次数到37扫描次数的聚苯胺膜电极,一方面比表面积明显增大，另一方面膜的整体电阻逐渐提高。随着扫描次数的增多，膜厚度迅速增大并线状结构的聚苯胺增长迅速，形成了具有多孔网状结构的多孔隙率的聚苯胺疏松层。37到61扫描次数的聚苯胺膜的增厚是短的聚苯胺链变长和FTO表面新的聚苯胺链的产生的结合。因此，13到61扫描次数的聚苯胺膜随着聚苯胺膜厚的增加颜色从透明-半透明浅绿色-深绿色变化。 可见，电化学循环伏安法在FTO导电玻璃表面制备聚苯胺膜可形成两种不同特点的聚苯胺层，分别为低空隙的紧密层和多孔性的疏松层。电解质溶液能够穿过疏松层而很少能进入紧密层。紧密层的增加相当于电池另加了一系列电阻，阻碍了电子的传输，导致了电池电压的下降。两种起相反作用的因素影响着聚苯胺对电极的电池性能，分别为膜的厚度增加所引起的薄膜电极的比表面积的增大和膜电极当中的电子传输阻抗的增加。13、25和37扫描次数的聚苯胺膜的聚苯胺膜当中紧密层和比表面积的增加占主导地位，因此电池的短路电压和光电转化效率逐步提高。37、49和61扫描次数的聚苯胺膜的聚苯胺膜当中疏松层和电极电子传输阻抗的增加占主导地位，导致电池的短路电压和光电转化效率逐步下降。因为，13到61扫描次数的聚苯胺膜的聚苯胺薄膜电极的比表面积在不断增加，引起电池填充因子的逐步提高。最后聚苯胺紧密层和疏松层双重影响之下，37扫描次数的聚苯胺对电极的电池性能为最佳，它的效率为4.95%，接近Pt对电极的5.41%，而它的电流密度比Pt电极的电流密度增加了11.6%。 本论文建立的电化学生长的聚苯胺薄膜理论模型将有助于开发高性能的基于其它更敏感 的导电聚合物染料敏化太阳能电池对电极或其它电器件。 关键词:电化学，聚苯胺，对电极，纳米结构，染料敏化太阳能电池 Electrochemical Fabrication Of Nanostructured Polyaniline Film Counter Electrode For Dye-Sensitized Solar Cells Tubshin Hreid ABSTRACT The current global energy shortage and environmental pollution have become two major problems. China's population, energy resources per capita is less than half the world average. The relative shortage of energy and resources has become a constraint on economic and social development. Development of green energy and renewable energy is an effective means of solving energy problem and reducing environmental pollution. The existing energy system, a small part from the direct use of solar, wind and water, most from the secondary energy - coal, oil, natural gas and nuclear energy. Among them, coal as the main fuel conventional power plants, oil and natural gas as the main urban transportation fuels in the energy supply have played a huge role, however, as environmental pollution caused by fossil energy use and limited reserves, development of environmentally friendly energy has become a topic of concern in the world. From the long-term point of view of energy and environment-friendly, utilization of solar energy is the safest, most environmentally friendly and one of the most long-term approach. The current solar energy as an important natural non-polluting energy more and more world attention. In China, there are about 100 million people are still not resolved and reliable power supply problems, mainly in Inner Mongolia, Xinjiang, Qinghai, Gansu, Inner Mongolia, the key area, wide area as pastoral herders living is relatively scattered, the majority of animal husbandry area and some rural areas need energy, farming and pastoral areas of new energy development is to adapt the commodity economy and improve people's living standard material base, hinder its development without electricity is a major reason, solve supply problems, strengthening national unity, to improve local living standards, local economic development, social stability, consolidating border are of great significance. So large-area solar cells for basic research, especially research higher photoelectric conversion efficiency, thin, light, easy to lay part of the solar cell electrode has important theoretical and practical significance. With the vast Inner Mongolia, long hours of sunshine and light intensity and other favorable natural conditions and rich resources of rare earth resources in Inner Mongolia to carry out research in line with local characteristics, very promising in this region has become a clean energy future large solar supply base. Is consistent with the characteristics of this region flexible dye-sensitized solar cell electrode area of basic research is particularly necessary. And conventional all-solid-type semiconductor light batteries, dye-sensitized solar cells (DSSC) is a new type of photoelectrochemical cell. Typically, the dye-sensitized solar cells with dye from the nanocrystalline titanium dioxide anode, the electrode and electrolyte composition. The principle is to use dyes made of inorganic semiconductor photoelectrochemical cell electrode becomes sensitive to visible light. Anode covered with a layer of titanium dioxide by the nanocrystalline thin films of transparent conductive glass composed of nanometer-sized electronic conduction through the interconnected network structure consisting of particles to be. Film thickness from a few hundred nanometers to tens of microns. Ruthenium dye molecules by functional groups (carboxyl or phosphate) adsorbed on the semiconductor surface chemistry, pore by the redox electrolyte containing filled, platinum-coated conductive glass as a photocatalyst electrode, composed of the load circuit. The general mechanism is: the light is absorbed by the dye, resulting in a rapid injection of semiconductor electronic conduction band, the adsorption of the dye present in the electrolyte phase through the triple-Iodide electron transfer to be recycled. The dye-sensitized solar cells are based on the most promising ruthenium dye adsorption immersed in liquid electrolyte nanocrystals of titanium dioxide to achieve, in which the nanocrystalline titanium dioxide and dyes in close contact to enhance the charge transfer, and expand the light absorption interface. Electrode is dye-sensitized solar cells is an important component of the redox electrolyte mainly for the regeneration power of the battery performance and cost reduction is important, platinum because of its excellent performance has been widely used in dye-sensitized solar cells as electrode materials, but the platinum materials scarce and expensive, there have been a platinum substitute research. Such as graphite, carbon black, carbon nanotubes and conductive polymers. Among them, polyaniline (PANI) is a well-known class of conductive polymers, low cost, simple preparation, good environmental stability, and restore a stable catalytic performance, used in rechargeable batteries, sensors, capacitors and other electrical components field. Synthesis of polyaniline materials are chemical oxidation polymerization and electrochemical synthesis. Chemical oxidation polymerization in solution is mainly caused by the oxidant to monomer polymerization of conductive polymers. Electrochemical Preparation of polyaniline is generally under acidic conditions in the aniline monomer solution, in the electrochemical cell system (three-electrode system), the voltage applied to the system or the use of current-driven reaction, the aniline monomer in the battery anode was surface oxidation polymerization, and finally at the anode surface in the adhesion of polyaniline. Compared to chemical oxidation polymerization, electrochemical synthesis in normal temperature and pressure conditions, simple operation, low cost, short reaction time, high purity polyaniline prepared, easy to control the polymerization process, no reaction by-products Clear advantages for further processing. This paper proposes a simple electrochemical method using dye-sensitized solar cells prepared by the method of polyaniline on the electrode, and successfully used as a dye-sensitized solar cell electrode, and on this basis, the establishment of in-situ theoretical model of the growth of polyaniline polymer. At room temperature by electrochemical cyclic voltammetry technique in fluorine-doped tin oxide (FTO) conductive glass surface in situ polymerization of polyaniline films of different thicknesses. Through the different segments of the cyclic voltammetry of polyaniline on the electrode surface scanning electron microscopy and atomic force microscopy, and the electrode cross-section SEM observation to study the morphology of polyaniline electrode surface and thickness. The study found: polyaniline prepared under the electrochemical method, the first conductive layer on the surface of FTO glass spherical nano-structured PANI thin, then increase as the number of scans, spherical structure of polyaniline layer gradually increased and more dense, and a linear structure of polyaniline gradually formed, and thus the formation of linear structure of PANI dominate, making the electrode surface is covered by the linear structure of polyaniline, and the linear structure of polyaniline has grown rapidly, forming a porous loose network structure of the PANI layer. In addition, FTO conductive layer covered about 200-300nm long strip of fluorine-doped tin oxide particles that are connected between the conductive layer average thickness of about 700nm. Spherical structure of 100nm or less in average particle size of polyaniline, electrochemical deposition of platinum nano particle size distribution between the 30-50nm, they have the atomic force microscope is easy to distinguish the different morphology and particle size. This paper established the electrochemical growth of polyaniline film theory model. Cyclic voltammetry studies have shown that the preparation of green imine-type conductive polyaniline in the FTO glass surface growth process: a continuous polymer composed of amino benzene ring and chain wrapped around the FTO glass surface to form polyaniline nanoparticles. The conductivity of polyaniline than metal poor. At first, the shape of the PANI nanoparticles of metal oxides in the surface of FTO glass easier to form, to obtain low porosity of the PANI layer close to the nanoparticles. Then layer of conductive polyaniline nanoparticles poor performance reasons and covered the gradual emergence of the linear structure of polyaniline. 13 to 37 scans scans of polyaniline film electrode, on the one hand significantly increased surface area, the other hand, the overall resistance of the membrane increased gradually. With the increase in the number of scans, film thickness increases rapidly and the rapid growth of linear structure of the polyaniline to form a porous network structure with multi-porosity porous layer of polyaniline. 37-61 scans of the polyaniline film thickness is the polyaniline chain variable-length short and FTO surface new generation of polyaniline chain combination. Therefore, the number of 13-61 scans polyaniline PANI film thickness increases with color from transparent - translucent light green - dark green change. It is logical that two distinct PANI layers formed on the conducting surface of the FTO glass, respectively, close the gap layer and the low porosity of the porous layer. Electrolyte solution can pass through the porous layer and rarely into the dense layer. Closely equivalent to the increase in cell layer plus a series resistance, hindering the electron transfer, leading to the battery voltage drop. Two kinds of counterproductive factors affecting the performance of polyaniline on the electrode of the battery, respectively, the thickness of the membrane caused by increased surface area of thin-film electrodes and membrane electrode which increases the electron transfer impedance increases. 13,25 and 37 scans of polyaniline films and polyaniline films were dense layer increases the surface area of the dominant, so the short-circuit battery voltage and gradually increase the photoelectric conversion efficiency. 37,49 and 61 scans of the polyaniline film were loose layer of polyaniline film and the electrode impedance increased electronic transmission dominates, leading to short-circuit the battery voltage and photoelectric conversion efficiency gradually decreased. Because, 13-61 scans of PANI film of polyaniline film electrode surface area is increasing, causing the battery to gradually increase the fill factor. Finally, close polyaniline layer and double layer under the influence of osteoporosis, 37 scans of polyaniline on the electrode of the battery performance is the best, its efficiency is 4.95%, close to the 5.41% Pt counter electrode, and its current density than the Pt electrode current density increased by 11.6%. This paper established the electrochemical growth of polyaniline film will help to develop theoretical models based on other more sensitive high-performance conductive polymer dye-sensitized solar cells on the electrode or other electrical parts. Key words: Electrochemistry, polyaniline, counter electrode, nanostructure, dye-sensitised solar cells