钙钛矿薄膜的结晶生长及界面层材料的研究

发布时间：2018-06-03 19:07

  本文选题：钙钛矿太阳能电池 + 退火温度　； 参考：《中国科学技术大学》2017年博士论文

【摘要】：近年来,钙钛矿太阳能电池由于制备工艺简单、成本低廉、可制备柔性器件且光伏性能高达22.1%等优势,吸引了人们的关注和研究。高效率的太阳能电池不仅依赖钙钛矿薄膜的质量和性质,而且取决于接触层的性质和能带结构。一方面,钙钛矿材料具有高的载流子迁移率、长的扩散系数、大的光学吸收系数和可调控的光学带隙等优越的性质,因而可以作为电池的光吸收层去实现载流子的产生、输运和分离。同时,钙钛矿薄膜的质量直接影响到电池的光伏性能。人们开发各种方法去实现高质量的钙钛矿薄膜,从而有效地减小载流子的复合和提高电池的性能,已是研究的热点之一;另一方面,与钙钛矿层相邻的接触层,其本身必须具备良好的光学、电学性能和恰当的能级位置,才能实现电荷载流子在界面有效的抽取和传输。本论文主要集中在两个方面开展:一是从钙钛矿薄膜的制备工艺入手,通过优化制备条件,获得高质量的薄膜,从而提高电池的光电转化效率;二是通过探索影响界面电荷抽取的关键因素,进一步提升电荷传输性能。具体的研究内容如下:在钙钛矿材料的制备过程中,退火温度极易影响溶剂的蒸发和薄膜的形核生长,从而改变薄膜表面的形貌。因此,研究退火温度对钙钛矿薄膜的影响,有利于优化电池的光伏性能。采用两步沉积技术制备CH_3NH_3PbI_3钙钛矿薄膜,揭示了退火温度和光学吸收强度,薄膜表面的晶粒尺寸及结晶性之间的依赖关系。实验结果表明,CH_3NH_3PbI_3薄膜表面的晶粒尺寸随着退火温度的升高而单调增加;当退火温度高于120 ℃℃,有碘化铅的出现且随着退火温度的增加,其含量进一步增大;CH_3NH_3PbI_3薄膜的光学吸收强度和电池的光伏效率随着退火温度的增加,先增大后减小,并在退火温度为120℃℃时同时获得了最优值。此外,通过优化两步沉积过程中的退火温度,钙钛矿太阳能电池的最优和平均光电转化效率分别达到了 17.61%和16.40%。这些结果证明了温度在钙钛矿薄膜制备中扮演至关重要的作用,同时,提供了一种优化电池效率的重要途径。钙钛矿太阳能电池的光伏性能依赖于薄膜之间的界面,因此,通过有效的界面能带处理,不仅有利于提高电池的电荷传输效率,还可以深入理解电荷转移的机理。通过在ZnO薄膜制备过程中加入不同含量的Sn(0≤x≤0.2),调控钙钛矿太阳能电池中ZnO电子传输层的能带结构的变化。研究发现,Zn1-xSnxO薄膜表面形貌和结晶性并无明显的变化;在0≤x≤0.2范围内,随着Sn含量的增加Zn1-xSnxO的功函数和光学带隙均出现V-型变化的趋势;Sn的掺杂调控钙钛矿太阳能电池的光伏性能,例如,光电转化效率、开路电压、短路电流和填充因子均出现V-型的变化。通过控制Sn的掺杂含量(0≤x≤0.2),获得了电池最优的光伏性能:光电转化效率为16.47%、开路电压为1.04 V、短路电流24.13 mAcm~(-2)和填充因子为65.62。
[Abstract]:In recent years, perovskite solar cells have attracted much attention due to their advantages of simple preparation process, low cost, flexible devices and photovoltaic performance of up to 22.1%. High efficiency solar cells not only depend on the quality and properties of perovskite films, but also depend on the contact layer properties and band structure. On the one hand, perovskite has the advantages of high carrier mobility, long diffusion coefficient, large optical absorption coefficient and adjustable optical band gap, so it can be used as the photoabsorption layer of the battery to realize the generation of carriers. Transport and separation At the same time, the quality of perovskite film directly affects the photovoltaic performance of the cell. People develop various methods to realize high quality perovskite films, thus effectively reducing carrier recombination and improving the performance of the battery, on the other hand, the contact layer adjacent to the perovskite layer, In order to realize the effective extraction and transmission of charge carriers at the interface, it is necessary to have good optical and electrical properties and appropriate energy level positions. This paper mainly focuses on two aspects: first, from the preparation process of perovskite film, through the optimization of preparation conditions to obtain high-quality thin films, thereby improving the photovoltaic conversion efficiency of the battery; The other is to further improve the charge transport performance by exploring the key factors that affect the interface charge extraction. The main contents are as follows: during the preparation of perovskite, the annealing temperature can easily affect the evaporation of solvent and the nucleation and growth of the film, thus changing the surface morphology of the film. Therefore, studying the effect of annealing temperature on perovskite film is beneficial to optimize the photovoltaic performance of the cell. CH_3NH_3PbI_3 perovskite thin films were prepared by two-step deposition technique. The dependence of annealing temperature, optical absorption intensity, grain size and crystallinity on the surface of the films was revealed. The experimental results show that the grain size on the surface of CH3NH3PbI3 thin film increases monotonously with the increase of annealing temperature, and when the annealing temperature is higher than 120 鈩，

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