Mechanistic understanding of the charge carrier trapping in CsPbCl3 perovskite nanocrystals.

The optical properties of CsPbCl3 perovskite nanocrystals (NCs) with varied sizes were studied in the temperature range from 80 to 320 K by steady-state and time-resolved photoluminescence (PL) spectroscopy. The CsPbCl3 NCs were synthesized with a hot-injection approach at reaction temperature of 140-180 °C. The PL emissions in NC films originate from localized excitons. It is found that NC films shows a significant decrease in PL intensity with increasing temperature while they exhibit a clear increase in PL lifetime from 80 K to around 250 K and then a reduction at high temperature. The abnormal temperature dependence of PL lifetimes in NC films is related to thermal activation of trapped carriers in the NCs. The change of average lifetimes with emission energy indicates the thermal degradation result from the loss of ligands on the surface of NC films. Moreover, the PL intensities, peak energies, and bandwidths of the NC films as a function of temperature are discussed detail.