Electronic surface states and dielectric self-energy profiles in colloidal nanoscale platelets of CdSe

Abstract

The electronic surface states and dielectric self-energy profiles in CdSe colloidal nanoscale platelets are explored by means of an original ab initio approach. In particular, we show how the different coatings deeply modify the quantum and dielectric confinement in CdSe nanoscale platelets. Molecular coating leads to an electronic band gap free of electronic surface states as well as an optimal surface coverage. The reduced blinking in CdSe nanoscale platelets is discussed. The theoretical method here proposed allows one to go beyond the popular empirical description of abrupt dielectric interfaces by explicitly describing the nanoplatelet surface morphology and polarisability at the atomic level. This theoretical study open the way toward more precise description of the dielectric confinement effect in any hybrid system exhibiting 2D electronic properties.

Excitons in core-only, core-shell and core-crown CdSe nanoplatelets: Interplay between in-plane electron-hole correlation, spatial confinement, and dielectric confinement

“…Reference [6] experiments have inferred a binding energy of 180 meV using multiparameter fitting of the extinction spectrum. More direct and systematic measurements would be desirable to confirm the actual magnitude, but the smaller value as compared to our prediction may be due to the fact that abrupt interface models tend to overestimate dielectric confinement [15], so our model (and also Refs. [4,16]) provide upperbound values.…”

“…The main physical factors inducing such differences are: (i) the intense interaction with organic ligands passivating their large surfaces [4,15,16], (ii) the presence of lateral confinement, and (iii) the possibility of growing heterostructures not only along the strong confinement direction, but also along the weakly confined one (so called core-crown NPLs) [17].…”

Decreasing the electronic confinement in layered perovskites through intercalation

“…We therefore used a method designed to compute ε ∞ profiles for nanoscale slabs and composite systems 10,51 to estimate the respective contributions from the organic and inorganic layers to the bulk ε ∞ value. Profiles of the high-frequency dielectric constant perpendicular to the layers ( ε ∞,⊥ ) in (IC 6 ) 2 [PbI 4 ] and (IC 6 ) 2 [PbI 4 ]·2I 2 are shown in Fig.…”

“…52,53 Taking advantage of our ab initio determination of the perovskites' nanoscale dielectric profiles 10,51 (Fig. 5), we refined this abrupt dielectric-interface approximation of the BSE for the first time to estimate the electron–hole coulombic interaction without experimental inputs, while simultaneously avoiding an unphysical divergence of the self-energy.…”

Dielectric Confinement Enables Molecular Coupling in Stacked Colloidal Nanoplatelets

“…m j z (m j ⊥ ) is the mass parallel (perpendicular) to the strong confinement direction of the NPL, V j bo is the potential bandoffset between the NPL and the organic environment, and E Σ the self-energy potential arising from the dielectric mismatch between the two materials. [22][23][24][25] Since the ratio of NPL/ligand dielectric constants fulfills ǫ in /ǫ out > 1, a charge inside the NPL creates a surface polarization field of the same (opposite) sign on the inner (outer) side of the NPL. 22,23 Σ is then repulsive inside the NPL and attractive in between NPLs.…”