Emission Properties and Ultrafast Carrier Dynamics of CsPbCl₃ Perovskite Nanocrystals

Fluence-dependent photoluminescence and ultrafast transient absorption spectroscopy are used to study the dynamic behavior of carriers in CsPbCl 3 perovskite nanocrystals. At low excitation fluences, the radiative recombination rate is outcompeted by significant trapping of the charge carriers which then recombine nonradiatively, resulting in weak photoluminescence. As fluence is increased, the saturation of trap states deactivates these nonradiative relaxation paths giving rise to an increase in photoluminescence at first. However, with further increases in fluence, Auger recombination of multiexcitons results in a decline in photoluminescence efficiency. Analysis of this behavior yields an absorption cross section at 400 nm (3.1 eV) of (0.24 ± 0.05) × 10 –14 cm 2 . Transient photoluminescence and absorption measurements yielded values for single exciton trapping lifetime (1.6 ± 0.7 ns), biexciton and trion lifetimes (20 ± 3 and 157 ± 20 ps, respectively), single exciton radiative lifetime (12.7 ± 0.2 ns), intraband cooling lifetime (290 ± 37 fs), and exciton–exciton interaction energy (10 ± 2 meV).