Surface Treatment via a Multifluorine-Containing Passivator for High-Performance Inorganic Perovskite Solar Cells

Metal-halide inorganic perovskites have gained great interest due to their excellent thermal stability and adjustable bandgaps for fabricating tandem solar cells. However, challenges such as significant nonradiative recombination by perovskite interfacial defects and unpleasant moisture stability have forced further improvements in the power conversion efficiency (PCE) and stability of inverted inorganic perovskite solar cells (PSCs). Herein, 3,5-bis(trifluoromethyl)benzylamine (TFBA) as a surface modifier was used to achieve these goals. It was found that the amino group in TFBA can provide electrons to coordinate with the undercoordinated Pb2+ on the surface of inorganic perovskite, thus mitigating surface defects. Moreover, TFBA contains two trifluoromethyl groups with hydrophobic properties, which can effectively prevent moisture from intrusion. Consequently, TFBA treatment resulted in remarkable improvement of the device open-circuit voltage by 110 mV, leading to a PCE of 20.4% under 100 mW cm–2 illumination, superior to that of the control cell (17.8%). The unencapsulated devices without treatment and treatment with TFBA can preserve their initial PCEs of 65 and 90%, respectively, after aging for 1150 h under ambient conditions.