Hot carrier extraction and ultrafast interfacial charge transfer in CsPbBr₃/carbon dot nanocomposites

Interfacial thermalized and non-thermalized charge transfer between CsPbBr₃ nanocomposites and carbon dots is studied using steady-state spectroscopy. Two types of carbon dots (CDs) were synthesized and characterized: one derived from amine-functionalized pyrene, and the other prepared using citric acid and ortho-phenylenediamine as precursor materials. Fourier transform infrared and X-ray photoelectron spectroscopy measurements have shown that the carbon dot synthesized from pyrene is amine-rich, whereas the carbon dot synthesized from citric acid is carboxylic acid-rich. The PL of CsPbBr₃ nanocomposites is quenched by both CDs, indicating charge transfer between perovskite nanocomposites and the carbon dots. Transient absorption measurements have shown ultrafast charge transfer from perovskite nanocomposites to bound CDs from non-thermalized and thermalized excitonic states. We observed non-thermalized charge transfer from CsPbBr₃ to CDs, with nearly 44% hot-hole transfer from CsPbBr₃ to CD^- _Pyr and 25% hot-electron transfer from CsPbBr₃ to CD^- _Cyan. The charge transfer from thermalized states is monitored from the bleach recovery kinetics of CsPbBr₃ with CDs, and the rates of charge transfer fall in the normal and inverted regions of the Marcus bell-shaped curve.