Ultrafast carrier thermalization in lead iodide perovskite probed with two-dimensional electronic spectroscopy

TL;DR

This study uses ultrafast two-dimensional electronic spectroscopy to directly observe and measure the rapid thermalization of charge carriers in lead iodide perovskites, revealing sub-10 fs to 85 fs timescales and their dependence on energy and density.

Contribution

It provides the first direct measurement of initial carrier thermalization dynamics in lead iodide perovskites with sub-10 fs resolution, highlighting carrier-carrier scattering as the dominant process.

Findings

Thermalization occurs within 10 to 85 fs.

Carrier scattering rates depend on excess energy and density.

Mobility estimates up to 500 cm^2 V^(-1) s^(-1) at low densities.

Abstract

In band-like semiconductors, charge carriers form a thermal energy distribution rapidly after optical excitation. In hybrid lead halide perovskites, the cooling of such thermal carrier distributions occurs on timescales of ~300 fs via carrier-phonon scattering. However, the initial build-up of the thermal distribution proved difficult to resolve with pump-probe techniques due to the requirement of high resolution, both in time and in energy. Here, we use two-dimensional electronic spectroscopy with sub-10fs resolution to directly observe the carrier interactions that lead to the formation of a thermal carrier distribution. We find that thermalization occurs dominantly via carrier-carrier scattering under the investigated fluences and report the dependence of carrier scattering rates on excess energy and carrier density. We extract characteristic carrier thermalization times from below 10 fs to 85 fs. These values allow for mobilities of up to 500 cm^2 V^(-1) s^(-1) at carrier densities lower than 2x10^19 cm^(-3) and limit the time for carrier extraction in hot carrier solar cells.