Guanidinium doping enabled low-temperature fabrication of high-efficiency all-inorganic CsPbI2Br perovskite solar cells

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019, Vol.7 (48), p.27640-27647
• Main Authors: Ma, Junjie, Qin, Minchao, Li, Yuhao, Zhang, Tiankai, Xu, Jianbin, Guojia Fang, Lu, Xinhui
• Format: Article
• Language: English
• Subjects: Bonding strength; Crystallization; Cubic lattice; Doping; Efficiency; Fabrication; Hydrogen bonding; Hydrogen bonds; Lattice strain; Low temperature; Orthorhombic phase; Perovskites; Phase transitions; Photovoltaic cells; Solar cells; Temperature requirements; X-ray scattering
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta10899h

All-inorganic perovskite CsPbI2Br usually requires a high fabrication temperature (higher than 200 °C) and suffers from an unwanted phase transition from a photo-active cubic phase to a photo-inactive orthorhombic phase. Here, we demonstrate an effective anti-solvent-free route to simultaneously stabilize the cubic phase and lower the fabrication temperature of perovskite solar cells with guanidinium (GA) cation doping. It is suggested that a trace amount of GA in the precursor could enter the substitutional sites to stabilize the cubic phase by relaxing the lattice strain and forming strong hydrogen bonds. State-of-the-art in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements reveal that GA could advance the crystallization of the cubic phase, indicating that the formation of the perovskite cubic phase experiences a lowered energy barrier with the assistance of GA, thereby resulting in a significant decrease of the fabrication temperature. An efficiency as high as 14.34% was achieved at a low fabrication temperature of 140 °C. With the help of GA, the device maintains ∼94% of its initial efficiency after being stored for 1000 h.