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.
Highlights
Methyl-substituted germanane is an emerging material that has been proposed for novel applications in optoelectronics, photoelectrocatalysis, and biosensors
Water intercalation switches the PL spectrum reversibly between a bright red peak centered around 1.97 eV significantly above the 1.62 eV bandgap for the hydrated material, and a broad band-tail emission for the dry one
The PL excitation spectrum of the 1.97 eV emission starts at 2.1 eV and has its maximum at 3.5 eV, demonstrating that this emission arises from strong electronic transitions involving electronic levels above the conduction band minimum and/or below the valence band maximum
Summary
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