Functional Metal-oxide Plasmonic Metastructures: Ultrabright Semiconductor Quantum Dots with Polarized Spontaneous Emission and Suppressed Auger Recombination

Abstract

We use localized surface plasmon resonances in metallic nanoantennas to suppress defect environment of colloidal quantum dots and to enhance and polarize their spontaneous emission. For this we study the interaction of such quantum dots with functional metal-oxide plasmonic metastructures consisting of an Au/Si Schottky junction in close vicinity of a Si/Al oxide charge barrier. We show that optically excited quantum dots can couple with such metastructures via their electric dipole fields, offering super-plasmonic processes that include the impact of hot electron generation and fixed negative charges at the Si/Al oxide junction. For metallic nanoantennas with small aspect ratios our results show that these metastructures can reduce the defect-induced nonradiative decay rates of quantum dots such that their lifetime can become significantly longer than those in the absence of such nanoantennas. For metallic nanoantennas with larger aspect ratios these structures lead to ultrahigh enhancement of exciton-plasmon coupling, making the spontaneous emission of quantum dots strongly polarized while increasing their emission intensities by about 50 times. These results show by keeping excitons in the cores of quantum dots, the metastructures suppress migration of photo-excited electrons to surface defects and, therefore, reduce Auger recombination. Coherent dynamics associated with the quantum dot-induced exciton-plasmon coupling is theoretically investigated.

Graphene/WS2 Nanodisk Van der Waals Heterostructures on Plasmonic Ag Nanoparticle-Embedded Silica Metafilms for High-Performance Photodetectors

“…Therefore, the spectrum seen in Figure h (graphene/WS 2 -ND/AgNP-metafilm) is the result of a weighted average of the spectra seen in Figure b, considering the size distribution of the AgNPs (Figure g). Considering the results shown in Figure b, we believe that the photoresponsivity presented in Figure b is the result of plasmonic enhancement of optical excitation at two major wavelength ranges. − The first happens around the band gap of WS 2 -NDs and can be involved with the interband excitons. The second occurs at the upper band edge (or excited states above the band gap) of the WS 2 -NDs, close to the overall major plasmonic peak of the AgNP-metafilm seen in Figure h (or that of graphene/WS 2 -ND/AgNP-metafilm), i.e., at 450 nm.…”

“…In this wavelength range, one expects that the plasmon field enhancement promotes excitation of the electron/hole pairs. 52,53 Considering the wide ranges of AgNP sizes (20−120 nm) as shown in Figures 2g and S4, the contributions of the stronger peaks beyond 520 nm in Figure 5b are most probably suppressed to some extent by the relatively smaller number of AgNPs with larger sizes. Despite this, since such peaks are quite broad, their presence can explain the broad spectrum of graphene/WS 2 -ND/AgNPmetafilm in Figure 2h (purple line), particularly the feature on its longer wavelength side.…”

Impact of the Plasmonic Metal Oxide-Induced Photocatalytic Processes on the Interaction of Quantum Dots with Metallic Nanoparticles

“…In the presence of a large number of defect sites (small quantum yields), one can expect large P enh values, while under the same plasmonic settings when the defect sites are suppressed, these factors become smaller. Recently, we showed one can use plasmonic effects not only to enhance the near fields experienced by QDs but also to suppress their DEs. − This makes QDs unique superemitters by increasing their quantum yields by both the Purcell effect and the quarantine of their excitons against the substrate and surface defect sites.…”

Plasmon-Assisted Suppression of Surface Trap States and Enhanced Band-Edge Emission in a Bare CdTe Quantum Dot

“…Hybrid quantum systems based on plasmonic nanostructures offer outstanding possibilities to control the emission dynamics of a single emitter. Recent experiments have shown localized surface plasmon-assisted suppression of the defect environment of colloidal QDs to enhance and polarize their spontaneous emission and energy transfer-based quenching and enhancement of emission from single QDs near metal surfaces. , Moreover, different routes have been developed for enhancing the multiphoton emission and suppression of blinking of semiconductor QDs. − Previous studies on the fluorescence enhancement of quantum emitters using plasmon coupling are mainly attributed to the overall fluorescence yield obtained, including the effect of excitation enhancement and increase in quantum efficiency. − A thousand-fold change in the radiative decay rate was also reported, , based on fluorescence lifetime measurements on ensembles of emitters. So far, reports at the single-emitter level are rare, − and none addresses bare QD systems.…”

“…Hybrid quantum systems based on plasmonic nanostructures offer outstanding possibilities to control the emission dynamics of a single emitter. Recent experiments have shown localized surface plasmon-assisted suppression of the defect environment of colloidal QDs to enhance and polarize their spontaneous emission 14 and energy transfer-based quenching and enhancement of emission from single QDs near metal surfaces. 15,16 Moreover, different routes have been developed for enhancing the multiphoton emission and suppression of blinking of semiconductor QDs.…”