碘化钾对两步法制备钙钛矿薄膜及其电池性能的影响

Effect of Potassium Iodide on Film Quality and Photovoltaic Performance of Perovskite Solar Cells Fabricated via Two-step Method

有机-无机杂化钙钛矿太阳电池因具有光电转化效率高和制备成本低廉等优点而备受关注。钙钛矿薄膜中的缺陷是限制钙钛矿电池性能进一步提升的重要因素,而缺陷调控又依赖于薄膜制备方法的发展和进步。两步法是制备钙钛矿薄膜和电池的主要方法之一,但目前对在两步法前驱液中引入添加剂如何影响钙钛矿薄膜结晶过程和缺陷密度的认识不足。本工作致力于利用光谱、X射线衍射、扫描电镜和电学测试等技术手段研究在两步法的铅盐溶液中引入碘化钾(KI)对卤化铅溶液、钙钛矿转化、缺陷密度和电池性能的影响。实验结果表明,适量KI的引入有利于高碘配位数铅碘配合物的生成,促进卤化铅向钙钛矿相的室温转化,并有效降低钙钛矿薄膜中的缺陷密度,钙钛矿电池的光电转化效率从无KI时的17.49%提高到19.17%。本工作的研究结果不仅有助于加深对两步法制备钙钛矿过程中结晶规律的理解,而且有助于进一步推动钙钛矿薄膜质量和器件性能的提升。

Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high photoelectric conversion efficiency and low preparation cost.An important factor limiting the further performance improvement of perovskite solar cells is defects existed in perovskite active layers.The passivation of these defects depends on the development of perovskite preparation techniques.The two-step method is one of the most popular methods to prepare perovskite films and photovoltaic devices.In order to fabricate high-quality perovskite films and high-efficiency solar cells,the modified two-step method via introducing additives has been developed.However,effects of additives introduced into the lead halide precursor on the crystallization process and defect density of perovskite films fabricated via the two-step method are not yet fully understood.In this work,the impacts of potassium iodide(KI)on colloidal properties of the lead halide precursor,perovskite transformation,film quality and cell performance were investigated by means of spectroscopy,X-ray diffraction,scanning electron microscopy and various electrical measurements.Our results show that the introduction of appropriate amount of KI facilitates the formation of iodide-rich iodoplumbates,which is beneficial to accelerating perovskite transformation from lead halide and improving perovskite film quality.The photoelectric conversion efficiency of the solar cell incorporating appropriate KI has been increased to 19.17%from 17.49%for the control device.The results of this work not only help to deepen the understanding of the crystallization of perovskite films in the two-step preparation process,but also help to further improve perovskite film quality and device performance.