Interplay between multipole expansion of exchange interaction and Coulomb correlation of exciton in colloidal II–VI quantum dots

Abstract

We study the effect of Coulomb correlation on the emission properties of the ground state exciton in zincblende CdSe/ZnS core-shell and in wurtzite ZnO quantum dots. We validate our theory model by comparing results of computed exciton energies of CdSe/ZnS quantum dots to photoluminescence and scanning near-field optical microscopy measurements. We use that to estimate the diameter of the quantum dots using a simple model based on infinitely deep quantum well and compare the results with the statistics of the atomic force microscopy scans of CdSe/ZnS dots, obtaining excellent agreement. Thereafter, we compute the energy fine structure of exciton, finding striking difference between properties of zincblende CdSe/ZnS and wurtzite ZnO dots. While in the former the fine structure is dominated by the dipole terms of the multipole expansion of the exchange interaction, in the latter system that is mostly influenced by Coulomb correlation. Furthermore, the correlation sizeably influences also the exciton binding energy and emission radiative rate in~ZnO dots.

GaAs quantum dots under quasi-uniaxial stress: experiment and theory

“…However, particularly for larger deviation of xx from zero, we see that uncorrelated CI slightly underestimate FSS compared with experiment, while the correlated CI gives much larger FSS than experiment. Given this limited agreement between theory and experiment, we have repeated the calculations including also the multipole expansion 65,66 of the exchange interaction and/or considering the nonlinear piezoelectricity [67][68][69][70] , yet both of the aforementioned changed the result within ∼ 2µeV from the values shown in Fig. 3 (c) and, thus, did not improve the agreement with experiment.…”

Electronic Structural Insight into High‐Performance Quantum Dot Light‐Emitting Diodes

“…Crystal phase engineering could potentially serve as a powerful tool to modulate the physical and chemical properties of materials. [ 20,21 ] In II–VI and III–V compound bulk materials (e.g., CdSe, CdS, and InP), wurtzite and zinc‐blende are two typical crystalline structures, where atomic layers are repeated with ABA stacking in the wurtzite structure while ABC stacking in the zinc‐blende counterpart ( Figure a,b). This discrepancy leads to reduced structure symmetry and a nonnegligible internal crystal field in the wurtzite structure, which has been predicted to be beneficial for the transfer and separation of photogenerated electrons and holes in bulk ZnS.…”