Field-Induced Broadening of Electroabsorption Spectra of Semiconductor Nanorods and Nanoplatelets

Abstract

We theoretically study the broadening of optical absorption spectra of monodisperse ensembles of randomly oriented nanorods and nanoplatelets exposed to a static electric field. It is found that the weaker quantum confinement inside nanoplatelets results in a much stronger field impact on their absorption than on the absorption of nanorods. The most notable manifestation of this impact is that the widths of the absorption lines in the nanoplatelets’ spectra peak as functions of the electric field strength. Both the maximal widths and the corresponding optimal field strengths are found to decrease with the largest dimensions of the nanoplatelets. In sharp contrast to this, the broadening of the nanorods’ absorption grows monotonously and saturates with the field strength. The high tunability of electroabsorption and the possibility to maximize its efficiency, revealed by our study, suggest semiconductor nanoplatelets as a promising material base for the next-generation electro-optic devices.

Electronic structure robustness and design rules for 2D colloidal heterostructures

“…Noticeable shift (>1 meV) only appears if an electric field above 100 kV cm À1 gets applied. The determined shifts are in good agreement with experimental values [34][35][36] obtained for CdSe NPLs where the stark shift can reach a few meV under electric fields of 100-200 kV cm À1 . The predicted shift also follows the expected quadratic dependence for a quantum well, according to the equation: 37 E BE ðz; FÞ ¼ E BE ðz; FÞ À 2 9…”

“…This also explains why current measurements based on thin-core objects only show small shifts. [34][35][36] On the other hand, to build a structure poorly sensitive to the electric field, one should use a more confined profile, where the ground state has an energy which stays far above the triangular part of the energy profile.…”

Morphology-induced phonon spectra of CdSe/CdS nanoplatelets: core/shell vs. core–crown

“…2 The free-standing ultrathin semiconductor layers, nanoplatelets (NPLs), can be synthesized by means of colloidal chemistry 3,4 and demonstrate sharp photoluminescence (PL) emission (full width at half maximum, FWHM < 12 nm), polarized ultrafast PL with a high quantum yield, [3][4][5] anisotropic light absorption, 6 and other very promising properties. [7][8][9][10][11][12][13] Raman spectroscopy has often been employed to study semiconductor nanostructures, 14 including colloidal nanocrystals (NCs). [15][16][17][18] In addition to fundamental knowledge about the elementary excitations, 19,20 the phonon spectra provide information on chemical composition, [21][22][23][24] strain, 24 and coupling to the environment.…”

Intraband optical activity of semiconductor nanocrystals

“…Our results indicate that even small perturbations of the nanocrystal electronic subsystem can produce intraband optical activity exceeding that of typical chiral molecules by a factor of 100 to 1000. Such strong electronic optical activity is inherent to semiconductor nanocrystals and results from the much larger dipole moments of electrons inside nanocrystals compared to the dipole moments in chiral molecules …”

“…Such strong electronic optical activity is inherent to semiconductor nanocrystals and results from the much larger dipole moments of electrons inside nanocrystals compared to the dipole moments in chiral molecules. 29,30 This article is organized as follows. In the next section, we discuss the general theory of optical activity in nanocrystals with chirally perturbed electronic subsystems.…”