First Principles Calculations of Nanoplatelet Heterostructures: Optoelectronic Properties*

Two-dimensional, atomically precise core-shell nanoplatelets (NPLs) have recently been synthesized with no sample inhomogeneity, leading to remarkable photoluminescence quantum efficiencies and tunable electronic properties dependent on NPL thickness [1]. Here we use Density Functional Theory and the Qbox code [2] to investigate the unique optoelectronic properties of CdS/CdSe core-shell NPLs. We show that, compared to a pure CdSe NPL of the same thickness, the band gap and dielectric constant of the core-shell NPLs decrease consistent with experimental results, corresponding to a larger exciton binding energy by approximately 30%. We attribute our findings to an expansion of the lattice constant of the core-shell NPLs in the axial direction, leading to a strain-induced modification of the electronic properties of the system. In contrast to nanoparticles, where the optoelectronic properties are governed by quantum confinement, we find that the properties of NPLs depend on a subtle interplay between quantum confinement and strain induced in the NPLs by the heterostructured interfaces.

[1] Hazarika, Fedin, Hong, Guo, Srivastava, Cho, Coropceanu, Portner, Diroll, Greenwood, Mazzotti, Galli, Klie, Talapin, Submitted.
[2] www.qboxcode.org