Passivation of positively charged cationic defects in perovskite with nitrogen-donor crown ether enabling efficient perovskite solar cells

Positively charged cationic defects deteriorate the performance and long-term stability of perovskite solar cells. Herein, a nitrogen-donor crown ether is introduced as a positive defect passivator. A high open-circuit voltage of 1.174 V, a superior fill factor of 82.15% and an efficiency of 24.07% are achieved. The PSCs exhibit enhanced operational, moisture and thermal stability. [Display omitted] •A18C6 passivates positively charged cationic defects (Pb2+, Cs+) in perovskite.•Perovskite solar cells obtain a PCE of 24.07 % with a Voc of 1.174 V.•Operational, moisture and heat stabilities of films and devices are enhanced. Positively charged cationic defects are the main source of defects in metal-halide perovskite solar cells. They determine the quasi-Fermi level of electrons under illumination and contribute to non-radiative recombination loss, causing an open-circuit voltage deficit. In addition, they act as ion migration pathways for halide hopping, thus deteriorating long-term stability. Herein, a nitrogen-donor crown ether as a positive defect passivator is developed, which demonstrates a soft Lewis base nature, a large donor number and a higher formation constant with positively charged cationic defects. Density functional theory calculation indicates that the electron-donating nitrogen atom dramatically increases the electron density of oxygen atoms, leading to a strong affinity with positively charged cationic defects (Pb2+ and Cs+). The electron trap density in perovskite is significantly reduced by 27 %, resulting in an increased build-in potential. By adding a small amount of nitrogen-donor crown ether to the precursor solution, the perovskite solar cells achieve an efficiency of 24.07 % with an open-circuit voltage of 1.174 V and a fill factor of 82.15 %. Moreover, the unencapsulated perovskite solar cells show a T80 lifetime of 510 h under continuous operation (1 sun equivalent illumination, maximum power point tracking condition, dry N2 atmosphere), and enhanced moisture and heat stability.