Theory of excitation transfer between two-dimensional semiconductor and molecular layers

TL;DR

This paper presents a theoretical study of how energy transfer occurs between a two-dimensional semiconductor and molecular layers, emphasizing the influence of geometry and molecular orientation on transfer efficiency.

Contribution

It introduces a detailed theoretical model incorporating quasi-momentum conservation and intermolecular coupling, using density-functional theory partial charges for accurate coupling calculations.

Findings

Transfer rates are highly sensitive to system geometry.

Optimizing molecular orientation significantly enhances transfer efficiency.

An operating regime is identified where in-scattering dominates over back-scattering.

Abstract

The geometry-dependent energy transfer rate from an electrically pumped inorganic semiconductor quantum well into an organic molecular layer is studied theoretically. We focus on F\"orster-type nonradiative excitation transfer between the organic and inorganic layer and include quasi-momentum conservation and intermolecular coupling between the molecules in the organic film. (Transition) partial charges calculated from density-functional theory are used to calculate the coupling elements. The partial charges describe the spatial charge distribution and go beyond the common dipole-dipole interaction. We find that the transfer rates are highly sensitive to variations in the geometry of the hybrid inorganic/organic system. For instance, the transfer efficiency is improved by orders of magnitude by tuning the relative orientation and positioning of the molecules. Also, the operating regime is identified where in-scattering dominates over unwanted back-scattering from the molecular layer into the substrate.