太阳能电池TiO₂陷光薄膜的制备与特性研究

【作者】 荣林艳；

【导师】 周继承；

【作者基本信息】 中南大学 ， 电子科学与技术， 2010， 硕士

【摘要】 提高光电转换效率是当前太阳能电池亟待解决的问题,在电池表面涂覆一层或多层光学性质匹配的陷光薄膜,减少电池表面光的反射损失,增加光的透射,是一种理想的解决方案。TiO2薄膜在可见光谱区内具有较高的折射率和较低的吸收率,透明波段中心(X=550nm)与太阳光的可见光谱波段相符合,是一种极具竞争力的陷光薄膜材料。本文利用直流反应磁控溅射法在玻璃和硅衬底上制备了TiO2薄膜,优化了工艺条件；用原子力显微镜、X射线衍射仪、紫外-可见光分光光度计等对样品的表面形貌、晶体结构、可见光透过率等特性进行了表征分析,研究了制备工艺与TiO2薄膜结构性能间的影响规律,提出了通过改变制备工艺单步制备双层陷光薄膜的方法,为降低陷光薄膜的制备成本、提高太阳能电池转换效率提供了新途径。实验结果表明,薄膜沉积速率随着氧流量比的增大先增大后减小,随着溅射功率的增加而增大,随着溅射气压的增加而减小。用直流反应磁控溅射方法可以制备出表面平整、无缺陷的TiO2薄膜。薄膜经500℃退火后,晶粒大小趋于一致,表面平滑致密,经900℃退火后,原子发生位移,TiO2薄膜由原先的柱状晶粒转变成了棱状晶粒,表面粗糙。在常温下制备的TiO2薄膜为非晶态,300℃退火后薄膜为锐钛矿结构,900℃退火后薄膜由锐钛矿结构转化为金红石结构。制备的TiO2薄膜在可见光及近红外光范围内均有较高的透射率。薄膜折射率在1.51～2.72(λ=600nm)之间,增加氧气流量比可以制备出低折射率的TiO2薄膜,高温退火可得到高折射率的TiO2薄膜。薄膜消光系数随着退火温度的升高而增大。比起金红石薄膜,锐钛矿薄膜具有更优的光学性能,更适合作陷光薄膜。60nm厚的TiO2薄膜具有很好的减反射效果,平均反射率仅为3.37%。更多还原

【Abstract】 At present, improving conversion efficiency of solar cells is an imperative problem to be solved, depositing a light trapping thin film matching with optical property on solar cells to reduce the solar cells’ light reflection and increase light transmission is an ideal scheme. TiO2 thin films have optimal optical characteristics with optimal refractive index and low absorption index in the visible region, and its transparent center wavelength (λ=550nm) well coincides with the visible band of sunlight. Therefore, TiO2 is a very competive material as a light trapping thin film.In this paper, TiO2 thin films were deposited on glass and Si wafers substrates by direct current (DC) reactive magnetron sputtering, and its process conditions were optimized. The morphology, structure, optical properties of TiO2 thin films were analyzed by atomic force microscopy, X-ray diffraction, ultraviolet and visible spectrophotometer, respectively. Effects of deposition conditions on thin films structure and properties were investigated. The method of one-step preparing double lays light trapping thin film by changing process conditions was proposed, which can be applied to reduce cost and improve conversion efficiency of solar cells.The experimental results show that the deposition rate first increases and then decreases as increasing of oxygen flow ratio, and increases as increasing of sputtering power, and decreases as increasing of sputtering pressure. Surface of the TiO2 thin films is flat and no defect. After RTA at 500℃, the grain size tends to be uniform, and surface of thin films becomes smooth and compact; after RTA at 900℃, atom displacement takes place, TiO2 thin films transform from columnar grain to prismatic grain, and its surface becomes rough. As-deposited TiO2 thin films are amorphous, and after RTA at 300℃were identified to become anatase, another transition from anatase to rutile occurred at 900℃.TiO2 thin films with a high transmission in visible and near infrared spectrum, as well as refractive indices ranging from 1.51 to 2.72 at a wavelength of 600 nm, were obtained. The low refractive index thin films were obtained by increasing oxygen flow ratio, while the high refractive index thin films were achieved by annealing the as-deposited samples at high temperature. The extinction coefficient increases as increasing of anneal temperature. The optical property of anatase is better than rutile’s, therefore, anatase is more suitable for light trapping thin film. When the thickness of thin film is 60nm, TiO2 thin films as light trapping thin films show good antireflection performance, and the weighted average reflectance is only 3.37%.更多还原