Revealing the Effects of Defects on Ultrafast Carrier Dynamics of CsPbI3 Nanocrystals in Glass

Embedding CsPbI3 nanocrystals (NCs) into glasses can improve the thermal and chemical stability of perovskite NCs, which is a critical factor limiting their applications. However, the presence of defects of CsPbI3 NCs in glasses strongly affects their photoluminescence (PL) efficiency. Upon heat treatment, the Stokes shift and Urbach energy of CsPbI3 NCs formed in the glasses decrease from 139 to 16 meV and from ∼85 to ∼30 meV, respectively. Using time-resolved spectroscopy and transient absorption spectroscopy analysis, fast trapping of charge carriers within 13.9–263.2 ps is observed, resulting in PL efficiency lower than 7% and lifetime 1 order of magnitude smaller than those of colloidal counterparts. Carrier trapping by surface defect charges the CsPbI3 NCs, leading to the red shift of the photobleaching band during the recovering process and the photoinduced absorption at a wavelength far below the band gap. Results reported provide a method to evaluate the effects of surface defects on the optical properties of a perovskite NC-embedded solid matrix.