Confinement and Exciton Binding Energy Effects on Hot Carrier Cooling in Lead Halide Perovskite Nanomaterials

The relaxation of the above-gap (hot) carriers in lead halide perovskites (LHPs) is important for applications in photovoltaics and offers insights into carrier-carrier and carrier-phonon interactions. However, the role of quantum confinement in the hot carrier dynamics of nanosystems is still disputed. Here, we devise a single approach, ultrafast pump- push-probe spectroscopy, to study carrier cooling in six different size-controlled LHP nanomaterials. In cuboidal nanocrystals, we observe only a weak size effect on the cooling dynamics. In contrast, two-dimensional systems show suppression of the hot phonon bottleneck effect common in bulk perovskites. The proposed kinetic model describes the intrinsic and density-dependent cooling times accurately in all studied perovskite systems using only carrier-carrier, carrier-phonon, and excitonic coupling constants. This highlights the impact of exciton formation on carrier cooling and promotes dimensional confinement as a tool for engineering carrier-phonon and carrier-carrier interactions in LHP optoelectronic materials.

Automated summary

In this study, the relaxation of hot carriers in lead halide perovskites (LHPs) and the role of quantum confinement in nanosystems were examined. Ultrafast pump-push-probe spectroscopy was used to study carrier cooling in different size-controlled LHP nanomaterials. The results showed that dimensional confinement has a significant impact on carrier-phonon and carrier-carrier interactions, highlighting its potential for engineering LHP optoelectronic materials.