Multiexciton generation in IV-VI nanocrystals: The role of carrier effective mass, band mixing, and phonon emission

TL;DR

This paper investigates how effective mass, band mixing, and phonon emission influence multiexciton generation in IV-VI nanocrystals, using a 4-band model and Green's function calculations, with relevance to PbS and PbSe experiments.

Contribution

It introduces a detailed 4-band effective mass model to analyze multiexciton generation, highlighting the impact of carrier effective mass and band mixing.

Findings

Maximized multiexciton efficiency with small, similar electron and hole effective masses.

Results align with recent experimental data on PbS and PbSe nanocrystals.

Impact excitation is comparable to Green's function-based calculations.

Abstract

We study the role of the effective mass, band mixing and phonon emission on multiexciton generation in IV-VI nanocrystals. A 4-band k dot p effective mass model, which allows for an independent variation of these parameters, is adopted to describe the electronic structure of the nanocrystals. Multiexciton generation efficiencies are calculated using a Green's function formalism, providing results that are numerically similar to impact excitation. We find that multiexciton generation efficiencies are maximized when the effective mass of the electron and hole are small and similar. Contact with recent experimental results for multiexciton generation in PbS and PbSe is made.