Proceedings of nanoGe Fall Meeting19 (NFM19)
DOI: https://doi.org/10.29363/nanoge.nfm.2019.152
Publication date: 18th July 2019
Semiconductor nanoplatelets are the colloidal analogous of epitaxial quantum wells. However, molecular coupling between epitaxial quantum wells --which is mediated by quantum tunneling across inter-well barriers and has been key to developing superlattices- has not been clearly demonstrated with platelets.
It is generally acknowledged that the organic ligands passivating the surfaces creates a high potential barrier preventing tunneling of carriers. Yet, recent experiments with CdSe nanoplatelets suggest that stacking of nanoplatelets gives rise to inter-platelet excitonic species revealed in the emission spectrum.[1]
In this presentation, we show theoretically that molecular coupling between colloidal semiconductor nanoplatelets with face-to-face orientation is indeed feasible. Unlike in epitaxial wells, the coupling is not mediated by mechanical tunneling but by Coulomb interaction in a dielectrically inhomogeneous environment. This a weaker, yet longer ranged interaction.
We study the case of two, three, four and five coupled nanoplatelets. The absorption spectra show distinct features and clear trends, with an unusual electronic structure resulting from the high symmetry of the system along the coupling direction. We predict experimental signatures which can be used to confirm the synthesis of molecular species. These point toward the formation of minibands with increasing number of platelets.
Our theoretical predictions not only set the ground for novel molecular physics behavior -mediated by dielectric confinement- but also hint that colloidal superlattices with coherent carrier transport, reminiscent of epitaxial quantum well superlattices, may be achievable.
Financial support from MINECO project CTQ2017-83781-P and UJI project B2017-59 is acknowledged.
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