Distribution of carrier multiplication rates in CdSe and InAs nanocrystals

TL;DR

This paper calculates the distribution of carrier multiplication rates in CdSe and InAs nanocrystals, revealing how size and energy influence efficiency, with implications for optimizing nanocrystal-based devices.

Contribution

It provides a detailed calculation of biexciton generation rate distributions in CdSe and InAs nanocrystals using a pseudopotential approach and Fermi golden rule, highlighting size and energy effects.

Findings

Biexciton generation rates have a broad distribution depending on exciton energy and nanocrystal size.

Efficiency decreases for nanocrystals larger than 3 nm in diameter within certain photon energy ranges.

Carrier multiplication becomes less efficient in larger nanocrystals, especially above 3 nm diameter.

Abstract

The distribution of rates of carrier multiplication (CM) following photon absorption is calculated for semiconductor nanocrystals (NCs). The NC electronic structure is described using a screened pseudopotential method known to give reliable description of NC excitons. The rates of biexciton generation are calculated using the Fermi golden rule with all relevant Coulomb matrix elements, taking into account proper selection rules. In CdSe and InAs NCs we find a broad distribution biexciton generation rates depending strongly on the exciton energy and size of the NC. The process becomes inefficient for NC exceeding 3 nm in diameter in the photon energy range of 2-3 times the band gap.