Time-resolved optical assessment of exciton formation in mixed two-dimensional perovskite films

TL;DR

This study uses femtosecond transient absorption spectroscopy to investigate exciton formation and binding energies in mixed 2D perovskite films, revealing the presence of Mahan excitons at high carrier densities.

Contribution

It provides the first detailed time-resolved analysis of exciton dynamics and binding energies in mixed 2D perovskites, including the observation of Mahan excitons.

Findings

Exciton formation observed from cooled band-edge carriers.

Quantified exciton binding energies for different phases.

Confirmed existence of Mahan excitons above Mott density.

Abstract

We report the observation of exciton formation from the cooled band-edge carriers in mixed two-dimensional hybrid organic-inorganic perovskites using femtosecond transient absorption spectroscopy. By monitoring the changes of bleach signal upon excitations with various photon energy, we are able to extract the values of exciton binding energy and the occupancies of carriers of free and bound states for each two-dimensional phase. We also confirm the existence of Mahan exciton when injected carrier density is above the Mott criterion.