Spectral fingerprint of quantum confinement in single CsPbBr$_3$ nanocrystals

TL;DR

This study investigates the quantum confinement effects in single CsPbBr3 nanocrystals at cryogenic temperatures, revealing size-dependent spectral features and polarization properties that enhance understanding of their light emission mechanisms.

Contribution

It provides a detailed analysis of the band-edge exciton emission in single nanocrystals, highlighting size-dependent spectral features and polarization behaviors in the intermediate quantum confinement regime.

Findings

Size-dependent bright-triplet exciton energy splittings

Identification of trion and biexciton binding energies

Spectral and polarization properties explained by dipole orientation

Abstract

Lead halide perovskite nanocrystals are promising materials for classical and quantum light emission. To understand these outstanding properties, a thorough analysis of the band-edge exciton emission is needed which is not reachable in ensemble and room temperature studies because of broadening effects. Here, we report on a cryogenic-temperature study of the photoluminescence of single CsPbBr$_3$ NCs in the intermediate quantum confinement regime. We reveal the size-dependence of the spectral features observed: the bright-triplet exciton energy splittings, the trion and biexciton binding energies as well as the optical phonon replica spectrum. In addition, we show that bright triplet energy splittings are consistent with a pure exchange model and that the variety of polarisation properties and spectra recorded can be rationalised simply by considering the orientation of the emitting dipoles and the populations of the emitting states.