Effective Inhibition of Phase Segregation in Wide‐Bandgap Perovskites with Alkali Halides Additives to Improve the Stability of Solar Cells
Xin Meng, Jianan Wang, Haixin Wang, Mengjie Li, Derun Sun, Xiaodong Hu, Jizhou He, Yu Peng, Jing Zhou, Rui Chen, Fumeng Ren, Sanwan Liu, Shasha Zhang, Yiqiang Zhang, Zhiguo Zhao, Zonghao Liu, Wei Chen
Abstract
Wide‐bandgap perovskites have attracted much attention due to their potential application in perovskite‐based tandem solar cells, which can surpass the theoretical efficiency up‐limit of single‐junction solar cells. However, photoinduced phase segregation remains one of the most intractable impediments that deteriorate the operational stability of wide‐bandgap perovskites solar cells. Herein, the effect of a series of alkali halides additives on the photoinduced phase segregation of wide‐bandgap perovskites with the composition of FA 0.8 Cs 0.2 Pb(I 0.7 Br 0.3 ) 3 (FA is formamidinium) is systematically studied. By coupling in situ time‐dependent photoluminescence technique, potassium chloride (KCl) is demonstrated to be the best in suppressing the photoinduced phase segregation. The reduced iodine vacancy defects owing to supplemented chloride ions and the coupling of potassium ions with the accumulated iodide ions at the grain boundaries lead to effective suppression phase segregation. As a consequence, the KCl‐modified wide‐bandgap perovskite solar cells present a champion efficiency of 19.34%, and the devices can maintain 93% of the initial efficiency after light soaking for 500 h with maximum power point tracking under 1 sun equivalent white light‐emitting diode illumination, much superior to the reference device without KCl modification only retaining 72% of its initial efficiency.