Relaxation dynamics of bimodally distributed CdSe quantum dots

Abstract

We study the dynamical behavior of excitons in a bimodal distribution of CdSe/ ZnSSe quantum dots by intensity dependent, temperature dependent, and time resolved photoluminescence. The effect of exciton localization is investigated, both experimentally and theoretically by identifying transfer mechanisms due to thermalization and redistribution of excitons. We observe a dominant exciton emission from high energy dots ͑QDs1͒ and weaker emission from low energy dots ͑QDs2͒ at 10 K and at low excitation levels. At high excitation densities a CdSe QD-precursor state becomes visible at the high energy side of the QDs1 emission. Temperature dependent photoluminescence studies reveal a thermally activated exciton transfer from QDs1 to QDs2 resulting in an enhanced QDs2 emission above 60 K. Time resolved photoluminescence measurements allow us to estimate the characteristic radiative and nonradiative decay rates as well as the trapping rate from the QD-precursor layer. The experimentally observed photoluminescence is reasonably reproduced using a coupled rate equation model.

Picosecond charge variation of quantum dots under pulsed excitation

“…7,8 The most precise information on the physical mechanisms involved in the excitation and light emission processes is usually supplied by single QD spectroscopy.…”

Annealing-induced bimodal size distribution of small CdSe quantum dots with white-light emission

“…The evolution of the PL spectra versus annealing temperature clearly reveals the behavior of QDs from adjacent contact to aggregation. The two‐focus size distribution of both colloidal QDs and self‐assemble QDs was studied in other works, which was called a bimodal size distribution . The obvious common point of the previously reported bimodal distributions about colloidal QDs is that they were all formed in the liquid state.…”

Electron States, Phonon-Assisted Relaxation and Tunneling in Self-Assembled Quantum Dot Molecules in an Electric Field

“…In those works, optical spectroscopy methods were used in stacked quantum dot molecules (QDMs) [1][2][3][4][5][6][7][8][9][10][11][12][13]. Miscellaneous mechanisms could be responsible for the observed properties.…”