Ultrathin Nanosheets of Oxo‐functionalized Graphene Inhibit the Ion Migration in Perovskite Solar Cells

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Abstract
Mixed cation/halide perovskites have led to a significant increase in the efficiency 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 film. As evidence of the formation of sharp crystals with different orientation within the perovskite film, moiré fringes are observed in transmission electron microscopy. Thus, a champion device with a power conversion efficiency (PCE) of 21.1% (the efficiency 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.
Funding Information
  • National Basic Research Program of China (2016YFA0202402)
  • National Natural Science Foundation of China (61674109, 91733301)
  • Natural Science Foundation of Jiangsu Province (BK20170059)
  • Collaborative Innovation Center of Suzhou Nano Science and Technology
  • Priority Academic Program Development of Jiangsu Higher Education Institutions
  • Higher Education Discipline Innovation Project
  • State Administration of Foreign Experts Affairs
  • Helmholtz-Zentrum Berlin für Materialien und Energie
  • Soochow University
  • Deutsche Forschungsgemeinschaft (392444269)

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