Ultrathin Nanosheets of Oxo-functionalized Graphene Inhibit the Ion Migration in Perovskite Solar Cells
Meng Li1,2,3, Wei-Wei Zuo2, Qiong Wang2, Kai-Li Wang1, Ming-Peng Zhuo1, Hans Köbler2, Christian E. Halbig,3 Siegfried Eigler,4* Ying-Guo Yang,5 Xing-Yu Gao,5 Zhao-Kui Wang, 1,* Yongfang Li, 3 and Antonio Abate2,6,*
1Institute of Functional Nano & Soft Materials (FUNSOM) Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices Soochow University Suzhou 215123, China
3Laboratory of Advanced Optoelectronic Materials College of Chemistry Chemical Engineering and Materials Science Soochow University Suzhou 215123, China
Mixed cation/halide perovskites have led to a signifcant increase in the effciency and stability of perovskite solar cells. However, mobile ionic defects inevitably exacerbate the photoinduced phase segregation and self-decomposition of the crystal structure. Herein, ultrathin 2D nanosheets of oxo-functionalized graphene/dodecylamine (oxo-G/DA) are used to solve ion migration in cesium (Cs)-formamidinium (FA)-methylammonium (MA) triple-cation-based perovskites. Based on the superconducting carbon skeleton and functional groups that provide lone pairs of electrons on it, the ultrathin 2D network structure can fit tightly on the crystals and wrap them, isolating them, and thus reducing the migration of ions within the built-in electric field of the perovskite flm. As evidence of the formation of sharp crystals with different orientation within the perovskite flm, moiré fringes are observed in transmission electron microscopy. Thus, a champion device with a power conversion effciency (PCE) of 21.1% (the effciency distribution is 18.8 ± 1.7%) and a remarkable fill factor of 81%, with reduced hysteresis and improved long-term stability, is reported. This work provides a simple method for the improvement of the structural stability of perovskite in solar cells.