Theory of optical absorption in semiconductor nanocrystals: From single nanocrystals to superlattices
Christophe Delerue a, Maryam Alimoradi Jazi b, Tim Prins b, Niall Killilea c, Wiel Evers d, Peter Geiregat e, Zeger Hens e, Wolfgang Heiss c, Arjan Houtepen d, Daniel Vanmaekelbergh b
a IEMN, UMR-CNRS 8520, Villeneuve d'Ascq, France
b Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands
c Institute -Materials for Electronics and Energy Technology, Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg, Fürtherstraße 250, Nürnberg 90429, Germany
d Delft University of Technology (TU Delft), D1.380, Building 58, Van der Maasweg 9,, Delft, Netherlands
e Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Ghent, Belgium
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#Sol2D19. Two Dimensional Layered Semiconductors
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Efrat Lifshitz, Cristiane Morais Smith and Doron Naveh
Invited Speaker, Christophe Delerue, presentation 318
Publication date: 16th July 2019

Recent progress in colloidal chemistry has enabled the fabrication of epitaxially-connected superlattices of PbX (X=Se, S, Te) nanocrystals with square or honeycomb geometry [1-2]. CdX nanocrystal superlattices can be derived using cation exchange process. In parallel, it is also possible to form hexagonal lattices in which the nanocrystals are still separated by their ligand shell. In this presentation, I discuss different aspects on the optical absorption process in these materials. It is shown that the absorptance of superlattices is considerably enhanced due to the epitaxial connections between neighbor nanocrystals. The resulting value is close to the quantum absorptance found in epitaxial two-dimensional films (quantum wells). I discuss the physics governing the variations of the aborptance from the case of isolated nanocrystals to closely-packed situations, i.e., hexagonal lattices of nanocrystals [3], epitaxial superlattices, up to the quantum well limit.In the case of superlattices in which the nanocrystals are epitaxially connected, I discuss the evolution of the local-field factor with the necking strength between neighbor nanocrystals.




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