Kinetic modelling of carrier cooling in lead halide perovskite materials

TL;DR

This paper develops a kinetic model to understand how hot and cold carriers interact and relax in lead-halide perovskites, revealing how carrier populations influence cooling dynamics and electron-phonon interactions.

Contribution

The paper introduces a comprehensive kinetic model that captures the effects of hot and cold carriers on cooling dynamics in lead-halide perovskites, advancing understanding of carrier relaxation mechanisms.

Findings

Cooling slows with more hot carriers due to hot-phonon bottleneck

Cooling accelerates with more cold carriers

Model simplifies to include carrier-carrier and carrier-phonon interactions

Abstract

The relaxation of high-energy "hot" carriers in semiconductors is known to involve the redistribution of energy between (i) hot and cold carriers and (ii) hot carriers and phonons. Over the past few years, these two processes have been identified in lead-halide perovskites (LHPs) using ultrafast pump-probe experiments, but the interplay between these processes is not fully understood. Here we present a comprehensive kinetic model to elucidate the individual effects of the hot and cold carriers in bulk and nanocrystal $CsPbBr_{3}$ films obtained from "pump-push-probe" measurements. In accordance with our previous work, we observe that the cooling dynamics in the materials decelerate as the number of hot carriers increases, which we explain through a "hot-phonon bottleneck" mechanism. On the other hand, as the number of cold carriers increases, we observe an acceleration of the cooling kinetics in the samples. We describe the interplay of these opposing effects using our model, and by using series of natural approximations, reduce this model to a simple form containing terms for the carrier-carrier and carrier-phonon interactions. The model can be instrumental for evaluating the details of carrier cooling and electron-phonon couplings in a broad range of LHP optoelectronic materials.