Photoluminescence decay of mobile carriers influenced by imperfect quenching at particle surfaces with subdiffusive spread

TL;DR

This paper extends a model of photoluminescence decay to include subdiffusive carrier spread, explaining complex, nonexponential decay kinetics influenced by imperfect surface quenching.

Contribution

It introduces a subdiffusion-based extension to the existing model, capturing the nonexponential decay kinetics observed in photoluminescence experiments.

Findings

PL decay is nonexponential under subdiffusion.

Surface reactions limit exciton quenching rather than diffusion.

The model aligns with complex decay kinetics observed experimentally.

Abstract

We recently presented a quantitative model to explain the particle-size dependence of photoluminescence (PL) quantum yields and revealed that exciton quenching is not diffusion controlled, but limited by surface reactions. However, the exciton decay kinetics has not yet been analyzed using our theoretical model. Here, we study kinetic aspects of the model and show that it should be extended to take into account subdiffusion rather than normal diffusion to maintain consistency with the observed complex decay kinetics; we also show that the PL decay kinetics is nonexponential even when the PL quenching is limited by surface reactions under subdiffusion. Our theoretical analysis of the PL quantum yield and the PL decay kinetics provides a comprehensive picture of mobile charge carriers, immobile polarons, and self-trapped excitons.