Effect of Electron–Hole Separation on the Spectral Diffusion of Small-Sized CdSe Quantum Dots under an External Electric Field

Abstract

Spectral diffusion occurs in semiconductor quantum dots (QDs) under an external electric field, resulting from the transition energy shift of one single dot during optical absorption and emission processes. The classical electric polarization model fails to interpret the spectral diffusion in some cases when strong quantum confinement Stark effects and large Stokes shifts exist in the small-sized QDs. Based on the two-process (optical absorption and emission) four-state (the ground-and excited-states involved in each process) model, the field-induced spectral shifts of the (CdSe) 33 and (CdSe) 34 structures, which are computed with the first-principles calculations, are well fitted by the dipole moment and static polarizability changes in the separate processes. Furthermore, the linear and the quadratic variations of the field-induced spectral shifts are interpreted with the compressible and the incompressible electron−hole separation distances, which are computed from the Kohn−Sham levels involved in the excited states. Our study provides the direct pieces of evidence on the hypothesis summarized experimentally that the electron transition energy increases with the decreasing electron−hole separation. As a result, the spectral shifts of one single QD, as well as the spectral diffusion of QDs, are then adjustable by tuning the direction and strength of the external field.

Advanced HIL strategies in QLEDs: V2O5 and PEDOT:PSS dual-layer for charge balance and electron leakage prevention

“…It is attributed to the Stark effect observed in closely packed quantum dots when subjected to an external electric field. 36 Fig. 4b reveals higher current density values in V 2 O 5 -based QLEDs across the entire voltage range, with the highest values recorded particularly in A8.…”

Hot Carrier Temperature Dynamics in Semiconductor Nanostructures: Full Lineshape Modeling of Ultrafast Time-Resolved Emission Spectra

“…Although it may have the potential to report on the carrier cooling, it would be necessary to perform additional control measurements to rule out any additional process contributing to the observed shift. In semiconductors, spectral diffusion is one such process, a consequence of quantum confinement Stark effect, leading to peak-frequency shift. , …”

“…In semiconductors, spectral diffusion is one such process, a consequence of quantum confinement Stark effect, leading to peak-frequency shift. 41,42 Overall, the peak-frequency shift can have contributions from processes other than carrier cooling and may lead to incorrect estimation of cooling time. Furthermore, although this method may provide carrier cooling time, it does not report on hot carrier temperatures.…”

Directionality and additivity effects of molecular acidity and aromaticity for substituted benzoic acids under external electric fields

“…Essential in many chemical and physical phenomena and processes, the impact of external fields has attracted noticeable attention lately in the literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] because it can influence the molecular structure, [17][18][19][20][21][22] chemical reactivity, [23][24][25][26][27][28] and other electronic properties. [29][30][31][32][33][34] In a previous study, we investigated the impact of uniform external electric fields on molecular acidity and aromaticity propensities for the benzoic acid molecule.…”