Effect of the A-Site Cation on the Biexciton Dynamics in Lead Bromide Perovskite Nanocrystals

A systematic and comprehensive understanding of different aspects of the carrier dynamics of lead halide perovskite nanocrystals (LHP NCs) is the key to improving the performance of this highly anticipated material. Recent research suggests that the A-site cation of LHP materials has a significant effect on their photophysical processes, but there is still a lack of a systematic study on how the A-site cation affects their biexciton dynamics. Herein, we fabricated Cs systematic and comprehensive understanding of different aspects of the carrier dynamics of lead halide perovskite nanocrystals (LHP NCs) is the key to improving the performance of this highly anticipated material. Recent research suggests that the A-site cation of LHP materials has a significant effect on their photophysical processes, but there is still a lack of a systematic study on how the A-site cation affects their biexciton dynamics. Herein, we fabricated CsPbBr3, MAPbBr(3), and FAPbBr(3) NCs with similar sizes and morphologies and conducted femtosecond transient absorption (FTA) experiments on them. By a global analysis, we found that all the FTA spectra of CsPbBr3, MAPbBr(3), and FAPbBr(3) NCs include three decay-associated spectra (DAS) components under high pump fluence, which, respectively, are attributed to hot carrier cooling, biexciton Auger recombination (AR), and exciton recombination. By analyzing the DAS component of biexciton of CsPbBr3, MAPbBr(3), and FAPbBr(3) NCs, we extract their biexciton AR lifetime and biexciton binding energy. It is found that the biexciton AR lifetime of APbBr(3) NCs becomes shorter as the A-site cation changes from Cs+ to MA(+) and to FA(+) (similar to 77 ps for CsPbBr3, similar to 56 ps for MAPbBr(3), and similar to 42 ps for FAPbBr(3)), while the biexciton binding energy of APbBr(3) NCs becomes greater as the A-site cation changes from Cs+ to MA(+) and to FA(+) (similar to 32 meV for CsPbBr3, similar to 39 meV for MAPbBr(3), and similar to 45 meV for FAPbBr(3)). We also investigated how the A-site cation of APbBr(3) NCs affects their hot carriers cooling time and found a consistent result as the literature's report (J. Am. Chem. Soc. 2019, 141, 3532-3540).

Automated summary

A systematic understanding of carrier dynamics in lead halide perovskite nanocrystals is crucial for improving their performance. Recent research has focused on the influence of the A-site cation on photophysical processes and biexciton dynamics. Experimental analysis reveals that changing the A-site cation affects the spectra and biexciton behavior, resulting in shorter biexciton Auger recombination lifetime and higher biexciton binding energy.