Broadband and Ultrafast Infrared Spectroscopy of n-doped HgSe Quantum Dots
Ashley Stingel a, Jari Leemans b, Poul Petersen a, Pieter Geiregat b
a Ruhr University Bochum, Germany, Universitätsstraße, 150, Bochum, Germany
b Physics and Chemistry of Nanostructures, Ghent University, Belgium, Belgium
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)
#SNI22. Semiconductor Nanocrystals I: Basic Science (synthesis, spectroscopy, electronic structure, device and application)
Online, Spain, 2022 March 7th - 11th
Organizers: Emmanuel Lhuillier, Sandrine Ithurria and Angshuman Nag
Contributed talk, Pieter Geiregat, presentation 063
DOI: https://doi.org/10.29363/nanoge.nsm.2022.063
Publication date: 7th February 2022

Colloidal nanocrystals (QDs) have been developed as excellent opto-electronic materials over the past 3 decades. Being used in applications as diverse as light emission, conversion and detection, they found their way mostly in those requiring interaction with visible or near-infrared radiation. Going further into the mid-infrared spectrum however, a plethorum of applications await in fields as defense, security, trace gas detection, imaging, etc. Over the past decade, giant leaps have been made using inter – and intraband processes in QDs to address this exciting wavelength range, resulting in solution processable photo-detectors with state-of-the-art performance at a fraction of the cost. [1]

As important as light detection is the ability to develop light emitting devices in the mid-infrared. Sources with broadband or coherent narrowband radiation would be disruptive in several fields. However, many properties of excitons and multi-excitons that enable these devices remain unexplored for these narrow gap materials, such as exciton cooling, multi-exciton interactions (shifts, Auger processes, …) and the fate of excitations in an environment full of quenching sites, i.e. non-radiative transfer of energy to surface ligands.

In this contribution, we show our recent work on applying ultra-broadband 1D mid-infrared spectroscopy to n-doped HgSe QDs. These advanced measurements provide for the first time a complete overview of the ultrafast time dynamics of these materials over the full spectral range, revealing intraband cooling, photo-induced absorption and multi-exciton shifts. Our results pave the way towards a full understanding of the (multi-) exciton physics of intraband colloidal nanomaterials.

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