Measuring Exciton Fine-Structure in Perovskite Nanocrystal Ensembles

TL;DR

This study demonstrates that advanced nonlinear spectroscopic techniques can resolve exciton fine-structure in perovskite nanocrystal ensembles despite inhomogeneous broadening and disorder, advancing understanding of their optoelectronic properties.

Contribution

It shows that nonlinear spectroscopies like transient absorption and 2D coherent spectroscopy can detect exciton fine-structure in disordered PNC ensembles, overcoming previous measurement limitations.

Findings

Nonlinear spectroscopies preserve polarization selection rules in PNC ensembles.

Simulations confirm these techniques can resolve fine-structure despite broadening.

Methods enable ensemble measurements previously limited to single nanocrystals.

Abstract

Lead-halide perovskite nanocrystals (PNCs) exhibit unique optoelectronic properties, many of which originate from a purported bright-triplet exciton fine-structure. A major impediment to measuring this fine-structure is inhomogeneous spectral broadening, which has limited most experimental studies to single-nanocrystal spectroscopies. It is shown here that the linearly-polarized single-particle selection rules in PNCs are preserved in nonlinear spectroscopies of randomly-oriented ensembles. Simulations incorporating rotational-averaging demonstrate that techniques such as transient absorption and two-dimensional coherent spectroscopy are capable of resolving exciton fine-structure in PNCs, even in the presence of inhomogeneous broadening and orientation disorder.