Numerical Study of Carrier Multiplication Pathways in Nanocrystalline and Bulk Form of PbSe

TL;DR

This study uses numerical modeling to analyze carrier multiplication mechanisms in PbSe nanocrystals and bulk, highlighting impact ionization as the dominant process and explaining experimental quantum efficiency trends.

Contribution

It provides a detailed numerical analysis of carrier multiplication pathways in PbSe, emphasizing impact ionization's role and size-dependent quantum efficiency.

Findings

Impact ionization is the main carrier multiplication mechanism.

Direct photogeneration contributes weakly to quantum efficiency.

Size scaling affects quantum efficiency in nanocrystals.

Abstract

Employing the interband exciton scattering model, we have performed a numerical study of the direct photogeneration and population relaxation processes contributing to carrier multiplication (CM) in nanocrystalline and bulk PbSe. We argue that in both cases the impact ionization is the main mechanisms of CM. This explains weak contribution of the direct photogeneration to the total quantum efficiency (QE). Investigated size scaling of QE in NCs and comparison to the bulk limit provide microscopic insight in the experimentally observed trends.