有机-无机钙钛矿薄膜结晶过程研究及器件优化

QIBEBT-IR > 仿生与固态能源系统研究组

	有机-无机钙钛矿薄膜结晶过程研究及器件优化
	王栋
导师	刘志宏 ; 逄淑平
	2015-05
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	材料工程
关键词	钙钛矿太阳能电池溶剂工艺优化
摘要	有机金属卤化物钙钛矿材料具有高效率和价格低廉的特点，在太阳能电池中有广泛的应用前景。近年来，通过对器件结构、钙钛矿薄膜的成膜性和结晶性的调控、界面优化等，使基于有机金属卤化物钙钛矿薄膜的太阳能电池效率从3.8%迅速增长到20.1%。目前用于制备钙钛矿薄膜的方法主要有一步溶液旋涂法、原位浸泡法（两步溶液法）、蒸发法和气体辅助的溶液法等。其中，一步溶液法与卷对卷大规模制备技术的匹配度最高，被看作是最有希望实现商业化大规模生产的钙钛矿薄膜制备工艺。一步溶液法制备的钙钛矿薄膜质量主要受钙钛矿前驱体种类、与溶剂的配位作用、钙钛矿结晶过程等因素的制约。基于一步溶液法，本文首先研究了溶剂体系对钙钛矿薄膜的形成过程的影响。以N,N-二甲基甲酰胺（DMF）和丁内酯（GBL）两种溶剂为例，分析了溶剂的配位作用强弱和溶剂自身沸点的差异对钙钛矿薄膜析出和结晶过程的制约作用，揭示了钙钛矿从DMF和GBL中析出结晶的机理，并探讨了在介孔太阳能电池结构中，钙钛矿薄膜的均匀性和晶格缺陷等因素对效率的影响。为进一步获得全覆盖、平整的钙钛矿薄膜，本文通过使用碘化铅（PbI2）和氯化铅（PbCl2）混合铅盐取代单一的PbI2或PbCl2铅源（混合铅前驱体方法），实现了钙钛矿薄膜中晶粒的形核和生长过程的分离，前驱体中PbI2和碘化甲胺（MAI）的快速反应生成了大量的钙钛矿小晶粒，这些小晶粒为钙钛矿的后续生长提供了形核中心。通过调节PbI2和PbCl2的比例可以调控钙钛矿结晶的速度，从而有效提升钙钛矿薄膜质量和对基底的覆盖率。采用混合铅前驱体法制备的钙钛矿薄膜具有良好的晶格取向性、高吸光率和长载流子寿命。而且在持续的高温加热中表现出了良好的形貌稳定性，因此有望应用于制备热稳定的钙钛矿太阳能电池。甲脒铅碘（FAPbI3）钙钛矿拥有比甲胺铅碘（MAPbI3）钙钛矿更宽的吸光范围和更好的热稳定性。本文将混合铅前驱体的工艺应用到FAPbI3钙钛矿电池的制备中，全面系统的优化了FAPbI3钙钛矿电池的效率。两种铅前驱体PbI2和PbCl2的使用，有效的调节了钙钛矿的结晶过程，使获得的FAPbI3薄膜形貌有了极大的改善。由于FAPbI3更高的热稳定性，这使得高温处理过的FAPbI3太阳能电池表现出较小的电池滞后现象和更高的稳定输出特性。
其他摘要	Organometal halide perovskite materials emerge as a new “gamer-player” in the field of photovoltaic cells because of their excellent properties of high efficiency and low cost. Recently, the efficiency of all solid state perovskite thin film solar cells has boomed from 3.8% to 20.1%. To realize high efficiency, it has been ambiguously shown that the morphology of the perovskite film is one of the most essential factors affecting the photovoltaic parameters. Various deposition techniques have been reported to fabricate perovskite thin films, including one-step spin-coating processing, in situ dipping method, vapor deposition, and vapor-solution hybrid deposition. To meet the commercial requirement of high throughput manufacturing processes, the one-step solution processing followed by thermal annealing is the most promising and universal method considering its compatibility of roll-to roll mass production on the flexible substrate. Various studies have proved that different precursors and their coordination effect with solvent molecule have a critical influence on both the morphology and the crystallinity of perovskite thin films. Based on one-step solution processing method, this paper discussed the effect of solvent on perovskite thin film morphology and crystallinity. Two typical solvent N,N-Dimethylformamide (DMF) and r-butyrolactone (GBL) are chosen to prepare perovskite precursor solution and fabricate solar cell devices. The influence of the coordination effect between solvent molecular and Pb2+ ion, as well as the solvent boiling point difference on the perovskite thin films are discussed and the mechanism how perovskite precipitates from DMF and GBL solutions is disclosed. To facilitate reproducible fabrication of compact perovskite thin film, mixed lead precursors of both PbI2 and PbCl2 (denoted as ML method) are applied to replace the conventional single lead source, which successfully separates the nucleation and growing process of perovskite crystallites. The rapid reaction of MAI with PbI2 in the precursor contributes preformed perovskite crystallite domains for sequential perovskite film growth and the overall formation rate of perovskite is tailed by PbI2: PbCl2 ratio in the precursor solution. The optimized MAPbI3−xClx film with preferred lattice orientation and compact nature exhibits high absorption of light and long-time preservation of photo generated charge carriers. Further, regardless of the textured crystal nature of MAPbI3−xClx, the as-fabricated film still exhibits a stable morphology upon long-time annealing, which indicates that the present protocol is insensitive to the thermal annealing condition and such film will contribute an outstanding thermally stable photovoltaic performance. Compared with MAPbI3 or MAPbI3−xClx, formamidine lead iodide perovskite (FAPbI3) process broader absorption range and better thermal stability. We applied ML method to fabricate FAPbI3 solar cells and systematically optimized the cell performance. The ML method efficiently modulated the perovskite crystallization process and promoted film morphology. Comparing with MAPbI3, the FAPbI3 is processed with higher temperature, thus FAPbI3 solar cells exhibit less hysteresis and better output stability.
作者部门	仿生能源与储能系统团队
公开日期	2015-06-15
学位类型	硕士 ; 学位论文
语种	中文
文献类型	学位论文
条目标识符	http://ir.qibebt.ac.cn/handle/337004/8102
专题	仿生与固态能源系统研究组
作者单位	中国科学院青岛生物能源与过程研究所
推荐引用方式 GB/T 7714	王栋. 有机-无机钙钛矿薄膜结晶过程研究及器件优化[D]. 北京. 中国科学院大学,2015.

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