Single charge and exciton dynamics probed by molecular-scale-induced electroluminescence

TL;DR

This paper introduces a nanoscale technique using time-resolved scanning tunnelling microscopy-induced luminescence to study single charge and exciton dynamics, revealing detailed insights into electroluminescence at the quantum level.

Contribution

It demonstrates the ability to track single charge and exciton dynamics with nanosecond resolution, overcoming previous spatial averaging limitations.

Findings

Single charges and excitons can be characterized at the nanoscale.

Kinetic models accurately reproduce electroluminescent transients.

TR-STML can be extended to other nanophotonic systems.

Abstract

Excitons and their constituent charge carriers play the central role in electroluminescence mechanisms determining the ultimate performance of organic optoelectronic devices. The involved processes and their dynamics are often studied with time-resolved techniques limited by spatial averaging that obscures the properties of individual electron-hole pairs. Here we overcome this limit and characterize single charge and exciton dynamics at the nanoscale by using time-resolved scanning tunnelling microscopy-induced luminescence (TR-STML) stimulated with nanosecond voltage pulses. We use isolated defects in C$_{60}$ thin films as a model system into which we inject single charges and investigate the formation dynamics of a single exciton. Tuneable hole and electron injection rates are obtained from a kinetic model that reproduces the measured electroluminescent transients. These findings demonstrate that TR-STML can track dynamics at the quantum limit of single charge injection and can be extended to other systems and materials important for nanophotonic devices.