Multidimensional Function Upgradation of All-Inorganic CsPbIBr2 Perovskite Film by Doping an Ionic Additive for Carbon-Electrode-Based Solar Cells

All-inorganic CsPbIBr2 perovskite solar cells (PSCs) recently demonstrated great superiority for application in tandem and semitransparent photovoltaics because of their excellent phase stability. However, compared to state-of-the-art PSCs, the inferior film quality is harmful for the photovoltaic performance improvement. Herein, a novel ionic additive, tetrabutylammonium hexafluorophosphate (TBAPF(6)), is employed to improve the all-inorganic CsPbIBr2 perovskite film quality and passivate detrimental defects. By assembly into carbon-electrode-based solar cells, a champion efficiency as high as 10.57% is achieved, which is much higher than that of a control device with 8.30% efficiency, mainly attributed to the suppressed non-radiative recombination. More importantly, the presence of alkyl chains and fluorine atoms in TBAPF(6) significantly increases the hydrophobicity of perovskite films and therefore improves the long-term stability under harsh conditions without encapsulation.