posted on 2021-11-30, 15:33authored byGur Lubin, Gili Yaniv, Miri Kazes, Arin Can Ulku, Ivan Michel Antolovic, Samuel Burri, Claudio Bruschini, Edoardo Charbon, Venkata Jayasurya Yallapragada, Dan Oron
Understanding exciton−exciton
interaction in multiply excited
nanocrystals is crucial to their utilization as functional materials.
Yet, for lead halide perovskite nanocrystals, which are promising
candidates for nanocrystal-based technologies, numerous contradicting
values have been reported for the strength and sign of their exciton−exciton
interaction. In this work, we unambiguously determine the biexciton
binding energy in single cesium lead halide perovskite nanocrystals
at room temperature. This is enabled by the recently introduced single-photon
avalanche diode array spectrometer, capable of temporally isolating
biexciton−exciton emission cascades while retaining spectral
resolution. We demonstrate that CsPbBr3 nanocrystals feature
an attractive exciton−exciton interaction, with a mean biexciton
binding energy of 10 meV. For CsPbI3 nanocrystals,
we observe a mean biexciton binding energy that is close to zero,
and individual nanocrystals show either weakly attractive or weakly
repulsive exciton−exciton interaction. We further show that,
within ensembles of both materials, single-nanocrystal biexciton binding
energies are correlated with the degree of charge-carrier confinement.