Hot Carrier Dynamics and Charge Trapping in Surface Passivated β-CsPbI3 Inorganic Perovskite.

Thermodynamically stable CsPbI3 inorganic perovskite has achieved high efficiency exceeding 20% with surface defect passivation, but a thorough understanding on the photophysics properties of surface passivated CsPbI3 inorganic perovskite is still lacking. Herein, we have used transient absorption spectroscopy to investigate the photophysical properties of β-CsPbI3 perovskites with and without passivation. The results indicate that the carrier trapping process has become slower because of the reduced deep defects that were varied to shallow defects due to surface passivation. The bimolecular recombination of β-CsPbI3 was also accelerated because of the improved carrier mobility after healing surface defects by passivation agents. Moreover, the efficient defect passivation can also elongate the hot carrier lifetime from 0.26 to 0.37 ps by impeding the charge trapping process. Our findings reveal that the defects passivation is beneficial to enhance defect tolerance, improve carrier transport, and slow down the hot carrier cooling for developing high-performance photovoltaics.