【作者】 曾宪光；

【导师】 庄稼；

【作者基本信息】 西南石油大学 ， 油气田材料与应用， 2013， 博士

【摘要】 太阳能是取之不尽、用之不竭的可再生清洁能源,利用太阳能的主要方式之一是太阳能光伏电池发电。当今太阳能光伏发电及其应用日渐广泛,现已逐步在油气田开发工程方面有所应用,为油气田提供服务。作为第三代太阳能发电装置的染料敏化太阳能电池(DSSC)具有制作工艺简单、转化效率较高、成本低廉等优点,是一种未来极具发展潜力的新型光伏电池,近年来已受到了各国研究者越来越多的关注和投入。迄今为止,针对DSSC,国内外许多学者己开展了大量的研究工作,并取得了一定的研究成果,但其应用仍然存在较多问题。例如,TiO2因其较宽的禁带宽度而只能吸收紫外区光线,致使对入射光的利用率不足,严重影响了DSSC的光电转化效率。纳米TiO2薄膜作为DSSC重要组成部分,是影响电池光电转换效率的关键因素之一。因此,围绕TiO2薄膜多样化制备技术的研究,如何调整纳米TiO2的禁带宽度,拓展其光谱响应范围,进而提高其太阳光利用率,是近期和今后DSSC的研究重点,具有很重要的应用价值和理论价值。本文以纳晶TiO2薄膜为研究对象,分别采用了阴极电沉积法、阳极氧化法、低热固相法、溶胶-凝胶法和水热法五种方法制备TiO2粉体及薄膜,并将其应用到DSSC中。利用了AFM、SEM、XRD、XRF、TG-DSC等手段对TiO2薄膜的表面形貌、物相结构、组分、热性能等进行表征分析,探讨了制备工艺参数对产物形貌和性能的影响及其部分产物的形成机理,研究了多种TiO2薄膜材料的光电流-光电压曲线(I-V曲线)和交流阻抗图谱(EIS图谱)特性,评定了其电池的光电性能。主要研究结论如下：(1)采用“阴极电沉积法”制备了TiO2纳米晶薄膜。用单因素方法研究了pH、电压、沉积时间等因素对电沉积的影响,获得了以Ti(SO4)2为钛源制备TiO2薄膜的最佳配方及工艺条件为10.0mL Ti(SO4)2,3.0mLH2O2,2.0mL HNO3,8.0mL NH3·H2O,20.0mL H2O,pH为1.5,电压为3.5V,沉积时间为20min。该TiO2纳米薄膜分布较均匀,其晶型为锐钛矿型,平均晶粒尺寸为10nm,其电池的光电转换效率为1.26%。浸渍掺铁将该TiO2薄膜的电池光电转换效率提高了21.4%,其电池光电转换效率达1.53%。(2)采用“阳极氧化法”制备了TiO2纳米管薄膜。以含有F-离子的水溶液作为电解质,研究阳极氧化参数对TiO2纳米管形貌的影响。当电压小于15V时,不利于TiO2纳米管生长：在15-30V电压范围,随着电压的增加,TiO2纳米管的管径也随之增大；当电压达到30V时,纳米管状结构被破坏,形成一种海绵状的无规则多孔结构。因此,适当增大电压有利于大孔径TiO2纳米管的形成。在20V电压、30min氧化条件下所制备的TiO2纳米管晶型为锐钛矿型,管径为100nm左右,其电池的光电转换效率为1.42%；对该电池进行TiCl4处理后,其电池光电转换效率达1.98%,比未进行TiCl4处理的效率提高了39.4%,交流阻抗实验结果验证了该结论。(3)采用“低热固相法+丝网印刷技术”制备Ni掺杂TiO2薄膜。以钛酸丁酯与六水合氯化镍直接固相反应,制备了纳米Ni-TiO2粉体及薄膜。所制备纳米Ni-TiO2薄膜呈海绵状多孔结构,分布较均匀,其薄膜晶型为锐钛矿型,平均晶粒尺寸约为20nm。与未掺杂TiO2相比,掺镍后促进了晶粒细化,其光电转换效率为2.13%,电池效率提高了约37.4%。以TiCl4处理Ni-TiO2薄膜,电池效率进一步提高,其电池光电转换效率达2.45%。(4)采用“溶胶-凝胶法+浸渍提拉技术”制备了TiO2纳米晶薄膜。通过正交试验法获得了制备TiO2薄膜的最佳配方：钛酸丁酯10.0mL,无水乙醇50.0mL,硝酸2.0mL,水1.OmL,聚乙二醇(20000)0.4g。在该条件下,其配方所制备的薄膜较为均匀,无裂纹,平均晶粒尺寸为12nnm左右,在100mW/cm2模拟太阳光照射下,其光电转换效率达3.72%。同时,在该配方的基础上制备了掺杂La-TiO2薄膜,经XRD测试,其结果表明：所制备的La-TiO2薄膜的晶型为锐态矿相结构。并且发现在掺镧TiO2纳晶薄膜中,随着掺杂摩尔比的增大,其衍射峰强度降低并宽化,表明镧掺杂有助于TiO2晶粒细化,抑制了晶粒生长。另外发现,随着掺杂摩尔比(0-1.5mol%)的增加,其光电转换效率也随之增加；当镧掺杂摩尔比为1.5mol%时,其光电转化率达到4.35%,比未掺杂电池提高了16.9%。对镧掺杂TiO2薄膜的机理分析表明,其光电转化率明显提高的主要原因在于,晶粒细化和形成杂质能级所致。(5)采用“水热法+丝网印刷技术”制备了锐钛矿型TiO2薄膜。水热法制备TiO2粉体配方为钛酸丁酯10.0mL、无水乙醇40.0mL、盐酸2.0mL、水1.0mL、三乙醇胺1.0mL。通过正交试验获得最佳制备条件为：水热温度为220℃、水热反应时间为24h、印刷层数为5层、热处理温度为550℃。此最佳工艺条件下电池的光电转换效率达5.53%。同时,在该配方的基础上制备了铒、镱掺杂TiO2薄膜。结果表明：铒、镱掺杂TiO2薄膜呈海绵状多孔薄膜,分布较均匀,铒、镱掺杂细化了TiO2晶粒。当0.5mol%Er+0.5mol%Yb共掺杂Ti02薄膜时,其组装电池的光电转换效率高达6.15%,比未掺杂时提高了11.2%,交流阻抗实验结果验证了该结论。(6)光阳极Ti02薄膜是DSSC的关键部件,它对DSSC的光电性能有重要的影响。据多样化制备及改性TiO2薄膜的研究可得出：采用“阴极电沉积法”制备的Ti02薄膜较均匀,方法有一定的特点,但其电池的光电转换效率偏低；“阳极氧化法”则通过调节阳极氧化电压、电解液浓度、pH、反应时间等因素可制备所需的TiO2纳米管阵列,预测其电池的光电转换效率可能会有很大的提升空间；“低热固相法”具有制备工艺简单、成本低、污染小、可大批量生产等优点,所制备Ti02薄膜呈海绵状多孔结构,其电池的光电转换效率还较低,继续研究仍有提升的空间,该方法适应性强,是制备Ti02粉体及薄膜方法中非常有发展前景的制备方法之一；“溶胶-凝胶法”具有设备简单、操作易控制、易工业化生产等优点,采用该法制备的Ti02薄膜较为均匀,其电池的光电转换效率还较低,仍需继续深入研究提高其光电转换效率；“水热法+丝网印刷技术”制备的Ti02薄膜呈海绵状多孔结构,其电池的光电转换效率较高,具有良好的工业化生产前景。此外,上述几种方法所制备的TiO2薄膜经改性处理后,其电池的光电转换效率都有不同程度的提高,可见,改性处理Ti02薄膜是提高其电池光电转换效率的一种有效方法。更多还原

【Abstract】 Solar energy is a renewable energy which will not be exhausted,and also it is a clean energy which will not produce any pollution.One of the main methods of solar energy utilization is solar photovoltaic power generation. With increasingly wide range of today’s solar power generation and its application,it has been gradually applied in the oil and gas development projects and provids services for the oil and gas fields.Dye sensitized solar cell (DSSC),the third generation of solar cell,has received more and more attention in recent years for its many advantages such as simple preparation procedure,high conversion efficiency and low cost, which make it become a promising new photovoltaic cells.Up to now, many scholars at home and abroad have carried out a lot of research work,and have made some achievements,but many problems still exist in its application for DSSC.For example,due to the wide band gap, TiO2can only absorb light of the ultraviolet region, which results in insufficient utilization of the incident light and seriously affects the photon-to-electron conversion efficiency of the DSSC.Nano-TiO2thin film as an important part of DSSC is one of the key factors for limiting photon-to-electron conversion efficiency of solar cell. Therefore, in the future, around the research on diversification of preparation technology of TiO2thin film, it is important to adjust the band gap of nano-TiO2,and expand its spectral response range to improve its sunlight utilization in the field of DSSC study.These researches have very important applicational and theoretical values.Based on nano-TiO2thin films as the research object,five kinds of methods such as cathodic electrodeposition method,anodic oxidation method,low thermal solid-state method,sol-gel and hydrothermal method had succeeded in preparing nano-TiO2powders and thin films,respectively.Then the nano-TiO2thin films were applied to DSSC.We used AFM,SEM,XRD,TG-DSC and XRF to characterize the morphologies, phase structure,composition and thermal properties of the nano-TiO2thin films.and analysed the effects of preparation process parameters on the morphologies and thermal properties of product.More over,its formation mechanisms of the part of the product are concluded.In addition,the characteristics of current-voltage curves (I-V curves) and AC impedance spectroscopy (EIS spectra) were studied for a variety of TiO2thin film materials,and the photoelectric properties of its cell were evaluated.The main research conclusions are shown as follows:(1) Nano-TiO2thin films were prepared by the cathodic electrodeposition method.The changes of process conditions such as voltage,pH and time during the preparation of TiO2thin films are discussed through single factor analysis method. Then the best formula and process conditions were achieved when Ti(SO4)2was used as titanium source,which included10.0mL of Ti(SO4)2,3.0mL of H2O2,2.0mL of HNO3,8.0mL of NH3·H2O,20.0mL of H2O,pH of1.5,the voltage of3.5V, depositing time of20min.Under this condition.a layer of uniform TiO2thin film formed and its TiO2crystal is anatase type, its size is10nm. The photon-to-electron conversion efficiency is up to1.26%. Fe-doped TiO2thin films are prepared by wet impregnation methods, its conversion efficiency can reach1.53%,increasing by21.4%.(2) TiO2nanotube thin films were prepared by the anodic oxidation method.Effects of anodic oxidation parameters on the morphology of TiO2nanotubes were studied in a aqueous solution containing F" ions as the electrolyte.When the voltage is less than15V, it does not favor the growth of TiO2nano tubes.When the voltage range is15-30V, the diameter of TiO2nanotubes also increases with the voltage increases.When the voltage reaches30V, the nanotube structures are destroyed and form a spongy-like porous structure with no rules. Therefore, it is conducive to the formation of large aperture TiO2nanotubes while the voltage is appropriately increased.Under the condition of voltage20V and oxidation time30min, the crystal of TiO2nanotubes is anatase phase, the diameter of TiO2nanotubes is around100nm, the photon-to-electron conversion efficiency of its cell was up to1.42%. After TiO2nanotubes are treated by using TiO2solution, the photon-to-electron conversion efficiency of its cell reaches1.98%, increasing by39.4%. AC impedance experiment results validated the conclusion.(3) Ni-doped TiO2thin films were prepared by the low thermal solid-state method plus screen printing technique.Ni-doped TiO2powders and thin films were prepared by direct solid phase reaction of butyl titanate and nickel chloride hexahydrate.The determination of Ni content is1.66wt.%.Ni-doped TiO2thin films prepared are not only spongy porous structure but also uniform film,its crystal is anatase type,and the average grain size is around20nm.Compared with undoped TiO2thin films, Ni-doped TiO2thin films promote the grain refinement.The photon-to-electron conversion efficiency is up to2.13%, increasing by about37.4%.The photon-to-electron conversion efficiency is further improved after TiO2solution treatment, its conversion efficiency is2.45%.(4) TiO2nanocrystalline thin films were prepared by the sol-gel method plus dip-coating technique.The best formula of reagents for the preparation of TiO2thin films was obtained by the orthogonal test method,which consists of10.OmL butyl titanate,50.0mL anhydrous ethanol and2.0mL nitric acid,1.0mL water,0.4g polyethylene glycol (20000).In this condition, uniform surface structure with no cracks is obtained in TiO2film.The average grain size is around12nm, and the film supplies photon-to-electron conversion efficiency of3.72%under100mW/cm2simulated sunlight irradiation.At the same time,La-doped TiO2thin films was prepared on the basis of the best formula.The results showed that Crystal phase of La-doped TiO2films prepared at450℃is anatase by XRD test.In La-doped TiO2crystal film,diffraction peaks become broader and their relative intensity decreases with the increase of doping molar content of La/Ti.Morever,it contributes to causing grain refinement and suppressing the grain growth, and photon-to-electron conversion efficiency also increases with the increase of doping molar content of La/Ti (0-1.5mol%).When La-doped molar ratio was1.5mol%, the photon-to-electron conversion efficiency reaches4.35%,and it increases as much as16.9%compared with no La in DSSC.In addition,mechanism analysis of La-doped TiO2thin film shows grain refinement and impurity energy level cause mainly the increase of photon-to-electron conversion efficiency.(5) Anatase TiO2nanocrystalline thin films were prepared by the hydrothermal method plus screen printing technique.Preperation formulations of TiO2powder was the mixture of10.0mL of tetrabutyl titanate,1.0mL water,and2.0mL of hydrochloric acid (37wt.%HCl) in40.0mL of anhydrous ethanol by the hydrothermal method.The optimum process condition of the preparation of TiO2thin films was obtained by the orthogonal test method.It included hydrothermal temperature of220℃, hydrothermal time of24h, printing layers of5layers, and heat treatment temperature of550℃.The TiO2thin films prepared in the optimum process conditions,as a photoanode,can supply a photon-to-electron conversion efficiency of5.53%.At the same time, rare-earth (Er,Yb) doped TiO2thin film was prepared on the basis of this formula.The results show that rare-earth (Er,Yb) doped TiO2thin film is spongy porous thin film with uniform distribution, and shows grain refinement compared with undoped TiO2thin film.When Er/Yb co-doped molar ratio is0.5mol%Er and0.5mol%Yb respectively,the photon-to-electron conversion efficiency is up to6.15%,increasing by11.2%than undoped TiO2thin film, which is consistent with AC impedance experiment result.(6) Photoanode TiO2film is a key component of DSSC,and it is the key of the improvement of the cell photon-to-electron conversion efficiency.It has an important influences on photovoltaic performance of solar cells.According to the study on diversification preparation and Modification of TiO2thin film,its results were shown as follows:TiO2film with uniformity was prepared by the cathodic electrodeposition method, and this methods have certain characteristics.but photon-to-electron conversion efficiency of the cells was lower;as for anodic oxidation methods,TiO2nanotube arrays were prepared by adjusting the factors such as oxidation voltage,electrolyte concentration, pH and oxidation time,and we predicted it might have a lot of improvement room for photon-to-electron conversion efficiency of the cell;TiO2thin films with spongy porous structure were prepared by low thermal solid-phase method with the advantages of a simple preparation process,less pollution,cheap and mass production.Photon-to-electron conversion efficiency of its cell is still lower,there is improvement room for its photon-to-electron conversion efficiency after continuing to be studied.This method is adaptable,and it is one of very promising preparation methods;there are the advantages of simple equipment, easy to control and easy to industrial production for sol-gel method.TiO2thin film prepared by using this method is more uniform,and photon-to-electron conversion efficiency of its cells is still lower.thus,it needs further research to improve photon-to-electron conversion efficiency;TiO2thin films with spongy porous structure were prepared by the hydrothermal method plus screen-printing technology.Its cell has higher photon-to-electron conversion efficiency, and there are good prospects for industrial production.In addition,after the processing of the modified TiO2thin film prepared by the aforementioned methods,photon-to-electron conversion efficiency of its cell can be increased to some extent.Therefore,it is a very effective method for TiO2film modified to improve photon-to-electron conversion efficiency of its cell.更多还原