Dynamics of Two Distinct Exciton Populations in Methyl-functionalized Germanane

TL;DR

This study reveals two distinct exciton populations in methyl-functionalized Germanane, showing their recombination dynamics, thermal transfer, and coupling to phonons, which advances understanding of its optical and electronic properties.

Contribution

It uncovers the existence and behavior of two exciton populations in methyl-functionalized Germanane, providing insights into their recombination and transfer mechanisms.

Findings

Two exciton populations with different lifetimes identified.

Thermally activated transfer occurs from shorter- to longer-lived excitons.

Longer-lived excitons migrate within disordered energy landscapes.

Abstract

Methyl-substituted Germanane is an emerging material that has been proposed for novel applications in optoelectronics, photoelectrocatalysis, and biosensors. It is a two-dimensional semiconductor with a strong above-gap fluorescence associated with water intercalation. Here, we use time-resolved photoluminescence spectroscopy to understand the mechanism causing this fluorescence. We show that it originates from two distinct exciton populations. Both populations recombine exponentially, accompanied by the thermally activated transfer of exciton population from the shorter- to the longer-lived type. The two exciton populations involve different electronic levels and couple to different phonons. The longer-lived type of exciton migrates within the disordered energy landscape of localized recombination centers. These outcomes shed light on the fundamental optical and electronic properties of functionalized germanane, enabling the groundwork for future applications in optoelectronics, light-harvesting, and sensing.