Year: 2025
Type: article
Abstract: The photodiode stack is the most effective design geometry for integrating colloidal nanocrystals (NCs) into optoelectronic devices dedicated to light emission and detection. Traditional designs rely on determining the absolute energy band alignment, followed by selecting suitable materials to transport charges (with energy levels resonant to the active material’s bands). Because of this method’s inherent limitations, we propose to explore an alternative approach where alkali metals are used to tune the absolute energy levels of the optically active layer. We illustrate this concept using lithium and cesium deposition onto narrow band gap NC films (i.e., HgTe and InAs), that are relevant materials for infrared optoelectronics. Our results show that work function shifts up to 0.9 eV can be achieved and that smaller alkalis are more effective at generating this shift. However, different behaviors are observed for HgTe and InAs. In the case of II–VI materials, the alkali acts as a pure dipole (i.e., no shift in the core level) and the film behaves as a bulk effective medium (i.e., no evidence of alkali intercalation). For III–V NCs, the alkali plays a dual role as both a dipole and a redox agent, making the alkali’s effect dependent on the NCs’ surface-to-volume ratio and the size of the alkali.
Institutions: Centre National de la Recherche Scientifique, Synchrotron SOLEIL, Sorbonne Université, Institut des NanoSciences de Paris, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA Grenoble, Institut de Recherche Interdisciplinaire de Grenoble, Université Grenoble Alpes, Université Paris Sciences et Lettres, Laboratoire de Physique et d’Étude des Matériaux
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: Automated monitoring in horticulture through spectral analysis with quantum dot detectors and high-resolution optical filters, Nanocrystals-based short-wave Infrared Imaging, Mixed Dimensional Heterostructures under 2D Ferroelectric control, G3667322904, Bright infrared light emitting diode with enhanced light-matter coupling, HgTe nanocrystals a new platform for THz optoelectronics, G5256542555, G5387359411, G5641435366, Infrared Sensors based on CQD, Photodetection in the Infrared with heavy metal-free QUANTum dots, In OPERAndo study of the electronic property modulation of 2D TWISTed hetero-bilayer, Automated monitoring in horticulture through spectral analysis with quantum dot detectors and high-resolution optical filters, Nanobeam soft X-ray microscope to unveil solar cell energy landscape
OpenAlex ID: W4417506523