Abstract
We examine exciton recombination, energy-, and charge transfer in multilayer CdS/ZnS quantum dots (QDs) on silver plasmonic resonators using photoluminescence (PL) and excitation spectroscopy along with kinetic modeling and simulations. The exciton dynamics including all the processes are strongly affected by the separation distance between QDs and silver resonators, excitation wavelength, and QD film thickness. For a direct contact or very small distance, interfacial charge transfer and tunneling dominate over intrinsic radiative recombination and exciton energy transfer to surface plasmons (SPs), resulting in PL suppression. With increasing distance, however, tunneling diminishes dramatically, while long-range exciton-SP coupling takes place much faster (>6.5 ns) than intrinsic recombination (~200 ns) causing considerable PL enhancement. The exciton-SP coupling strength shows a strong dependence on excitation wavelengths, suggesting the state-specific dynamics of excitons and the down-conversion of surface plasmons involved. The overlayers as well as the bottom monolayer of QD multilayers exhibit significant PL enhancement mainly through long-range exciton-SP coupling. The overall emission behaviors from single- and multilayer QD films on silver resonators are described quantitatively by a photophysical kinetic model and simulations. The present experimental and simulation results provide important and useful design rules for QD-based light harvesting applications using the exciton-surface plasmon coupling.
Highlights
Semiconductor quantum dots (QDs) have attracted great attention in diverse applications ranging from optoelectronic devices such as single photon sources and light emitting diodes (LED) to biological imaging because of their excellent optical properties and ease of chemical synthesis1–3
We examine exciton recombination, energy, and charge transfer in single-and multilayer CdS/ZnS quantum dots (QDs) on silver plasmonic resonators using photoluminescence (PL) and excitation spectroscopy along with photophysical kinetic modeling and simulations
Result and Discussion Exciton-Surface plasmons (SPs) coupling in QD monolayers on Ag resonators
Summary
Energy-, and charge transfer in multilayer CdS/ZnS quantum dots (QDs) on silver plasmonic resonators using photoluminescence (PL) and excitation spectroscopy along with kinetic modeling and simulations. Semiconductor quantum dots (QDs) have attracted great attention in diverse applications ranging from optoelectronic devices such as single photon sources and light emitting diodes (LED) to biological imaging because of their excellent optical properties and ease of chemical synthesis1–3 Whether they are pumped by photoexcitation or carrier injection, electron-hole pairs (excitons) are generated and subsequently recombine to emit light through radiative relaxation or to release heat through non-radiative relaxation. We examine exciton recombination, energy-, and charge transfer in single-and multilayer CdS/ZnS quantum dots (QDs) on silver plasmonic resonators using photoluminescence (PL) and excitation spectroscopy along with photophysical kinetic modeling and simulations. Instead of relaxing via non-radiative recombination, they can couple
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