Transient currents in a molecular photo-diode

TL;DR

This paper investigates light-induced transient currents in a molecular diode using a HOMO-LUMO model, analyzing charge transmission mechanisms and the impact of asymmetric electrode coupling on current behavior.

Contribution

It introduces a kinetic framework for transient current analysis in molecular diodes, including expressions for hopping and tunneling components, and explores the effects of molecular charging and electrode asymmetry.

Findings

Transient currents are linked to molecular charging initiated by photo excitation.

Asymmetric molecule-electrode coupling can cause transient currents to surpass steady state currents.

Detailed analysis of resonant and off-resonant charge transmission processes.

Abstract

Light-induced charge transmission through a molecular junction (molecular diode) is studied in the framework of a HOMO-LUMO model and in using a kinetic description. Expressions are presented for the sequential (hopping) and direct (tunneling) transient current components together with kinetic equations governing the time-dependent populations of the neutral and charged molecular states which participate in the current formation. Resonant and off-resonant charge transmission processes are analyzed in detail. It is demonstrated that the transient currents are associated with a molecular charging process which is initiated by photo excitation of the molecule. If the coupling of the molecule to the electrodes is strongly asymmetric the transient currents can significantly exceed the steady state current.