氯掺杂对CH3NH3PbI3太阳能电池材料气相生长机理、界面结构及其性能影响的同步辐射研究

In recent years, chlorine doped CH3NH3PbI3 perovskite films have attracted extensive attentions due to their excellent crystallinity and charge transport properties. But its oriented growth characteristic prevents the accurately determination of the fully crystal structure by conventional characterization methods, which leads that the exact role of doping element Cl is still unclear so far, and some key issues, such as the thin-film preparation technology, growth mechanism, and interface structure, need to be solved. In view of above questions, a novel Cl-assisted vapor deposition method is innovatively used to prepare controllably the chlorine doped perovskite films in this proposal, and the crystal structure and the electronic band structure are systematically investigated by the advanced synchrotron radiation experimental techniques, which is associated with the performance of the prepared solar cells. We will mainly focus on the effect of the experimental parameters on the thin-film quality and device performance. Some important information, such as the occupying position of doping ions, lattice distortion, crystal growth orientation, local atomic environment, and the structures of the electronic band and interface, will be studied in-depth by the synchrotron radiation-based SRPES, NEXAFS, EXAFS, and GIWAXS techniques, combining with the density functional theory calculations. Based on the successful implementation of this project, it is expected to built the reasonable composition-structure-performance relation model, and reveal the growth mechanism of this kind of materials and the detailed role of Cl element, and provide important theoretical basis for the development of high-performance perovskite solar cells.

近年来由于氯掺杂CH3NH3PbI3钙钛矿薄膜具有优异的结晶成膜和电荷传输性能而引起广泛关注。但鉴于其取向生长特性，常规表征尚不能进行精确结构解析，导致掺杂元素Cl的具体作用还不清楚，相应薄膜制备工艺、生长机理及界面结构等关键问题也亟待解决。针对上述难题，本项目拟创新性地采用Cl元素协助的气相沉积方法，可控制备Cl掺杂钙钛矿薄膜；结合先进同步辐射实验技术，系统研究其晶体结构和电子能带结构，进而与所制电池性能相关联。项目将主要探索实验参数对薄膜质量和器件性能的影响规律；采用同步辐射SRPES、NEXAFS、EXAFS及GIWAXS，结合密度泛函理论计算，重点研究掺杂离子格位占据、材料晶格畸变、结晶生长取向、原子局域环境、电子能带及界面结构等重要信息。通过本项目的实施，可望建立合理的材料成分-结构-物性关系模型，揭示该材料的生长机理和Cl元素作用机制，为研发高性能钙钛矿电池提供重要的理论依据。

近年来由于氯掺杂CH3NH3PbI3钙钛矿薄膜具有优异的结晶成膜和电荷传输性能而引起广泛关注。但鉴于其取向生长特性，常规表征尚不能进行精确结构解析，导致掺杂元素Cl的具体作用还不清楚，相应薄膜制备工艺、生长机理等关键问题也亟待解决。针对上述难题，本项目拟创新性地采用Cl元素协助的CVD气相沉积方法，可控制备Cl掺杂钙钛矿薄膜材料及高效电池器件，并结合先进同步辐射实验技术以揭示Cl元素的关键作用。项目主要研究内容包括Cl掺杂CH3NH3PbI3-xClx钙钛矿电池、Cl/Cs掺杂MA0.85Cs0.15PbI3-xClx钙钛矿电池及CsPb(IxBr1-x)3无机钙钛矿电池的材料生长、薄膜常规与同步辐射表征、器件光伏性能等研究工作。经过三年研究，本项目成功探索出钙钛矿电池的新型CVD气相沉积工艺，该技术具有设备简单、薄膜质量高、重复性佳、可控性强、可工业化应用等优点，已获得两项授权专利。同时，我们采用CVD工艺结合Cl掺杂技术，研制出17.82%的高效钙钛矿电池，达到CVD气相法制备的较好水平。研究表明：Cl的引入会对薄膜成核生长及结晶有一定影响，对钙钛矿薄膜的气相生长过程具有加速效应，但最终会从薄膜中升华消失；同时，Cl元素具有缺陷修复和种子晶协助生长功能，Cl掺入会形成CH3NH3PbI3-xClx中间相，起到辅助结晶作用，可提高薄膜质量，进而有效提高电池效率。本项目取得了较为丰硕的研究成果：发表论文16篇，以第一及通讯作者发表SCI论文10篇，包括JPCL、CC、JMCA、ACS ami、Chem. Eng. J及JMCC等一区和自然指数高水平论文6篇；发表于JPCL的论文被编辑选为Top Selected Papers in the Physical Chemistry of Energy Materials 2016−2017，引用75次；而前期钙钛矿电池CVD制备论文还入选ESI高引论文；申请发明专利10项，授权5项。本项目的成功实施，可望推动CVD气相沉积技术在钙钛矿电池领域的进一步应用，可为研发高性能钙钛矿电池提供理论依据，因而具有重要的科学意义及潜在的应用前景。