A relationship between the surface composition and spectroscopic properties of cesium lead bromide (CsPbBr₃) perovskite nanocrystals: Focusing on photoluminescence efficiency

We have previously developed CsPbBr₃ NCs exhibiting a tremendously high photoluminescence (PL) and structural stability by adding ZnBr₂. However, understanding of these outstanding properties is lacking due to the absence of spectroscopic analyses, such as spectral or dynamical characteristics. In this work, we conducted a comparative analysis of photophysical properties for conventional-CsPbBr₃ NCs and ZnBr₂-CsPbBr₃ NCs. First, we analyzed the blinking traces by comparing the single crystal PL intermittency. It has been found that the PL quantum yield of CsPbBr₃ NCs is gradually decreasing at the ensemble level, resulting from a significant activation of the Auger-induced blinking. Furthermore, the time-resolved TA dynamics supports the fact that Auger-type energy transfer accelerates the hot carrier cooling time, and thereby the Auger-induced blinking behavior in the band-edge state becomes dominant over time. Here, ZnBr₂-CsPbBr₃ NCs showed a low multiexciton Auger amplitude and therefore had a stable PL emission compared with conventional-CsPbBr₃ NCs. Finally, we suggest that both NCs differ in intraband spacing possibly due to capping ligands, finally leading to a suppressed Auger process and higher stability for ZnBr₂-CsPbBr₃ NCs.