Browse
Submit Data
Databases
API
Help

Dataset Information

37 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Phonon-assisted up-conversion photoluminescence of quantum dots.

ABSTRACT: Phonon-assisted up-conversion photoluminescence can boost energy of an emission photon to be higher than that of the excitation photon by absorbing vibration energy (or phonons) of the emitter. Here, up-conversion photoluminescence power-conversion efficiency (power ratio between the emission and excitation photons) for CdSe/CdS core/shell quantum dots is observed to be beyond unity. Instead of commonly known defect-assisted up-conversion photoluminescence for colloidal quantum dots, temperature-dependent measurements and single-dot spectroscopy reveal the up-conversion photoluminescence and conventional down-conversion photoluminescence share the same electron-phonon coupled electronic states. Ultrafast spectroscopy results imply the thermalized excitons for up-conversion photoluminescence form within 200 fs, which is 100,000 times faster than the radiative recombination rate of the exciton. Results suggest that colloidal quantum dots can be exploited as efficient, stable, and cost-effective emitters for up-conversion photoluminescence in various applications.

SUBMITTER: Ye Z

PROVIDER: S-EPMC8277828 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

CO2 phonon mode renormalization using phonon-assisted energy up-conversion.

Project description:Molecular dissociation under incident light whose energy is lower than the bond dissociation energy has been achieved through multi step excitation using a coupled state of a photon, electron, and multimode-coherent phonon as known as the dressed photon phonon (DPP). Here, we have investigated the effects of the DPP on CO2, a very stable molecule with high absorption and dissociation energies, by introducing ZnO nanorods to generate the DPP. Then, the changes in CO2 absorption bands were evaluated using light with a wavelength longer than the absorption wavelength, which confirmed the DPP-assisted energy up-conversion. To evaluate the specific CO2 modes related to this process, we measured the CO2 vibration-rotation spectra in the near-infrared region. Detailed analysis of the 3ν3 vibrational band when a DPP source is present showed that DPP causes a significant increase in the intensity of certain absorption bands, especially those that require higher energies to activate.

| S-EPMC3840381 | biostudies-other

Photoluminescence investigations of sulfur quantum dots synthesized by a bubbling-assisted strategy.

Project description:Sulfur quantum dots (S-dots) emerge as promising luminescent materials owing to their remarkable optical properties. However, the mechanisms of their formation and photoluminescence remain concealed. We reveal these mechanisms by the bubbling-assisted synthesis and spectroscopic study of S-dots formed from sulfur ions produced by the alkaline oxidation of bulk sulfur under the passivation of PEG. The emission colour of the S-dots depends on the size, explained by the quantum confinement effect. The dots' luminescent quantum efficiency is strongly affected by the surface sulfur species, which is optimized by the proper surface oxidation. The simple synthesis, excellent luminescence properties, and metal-free nature attract S-dots to optoelectronic and electroluminescence applications.

| S-EPMC9417840 | biostudies-literature

Giant up-conversion efficiency of InGaAs quantum dots in a planar microcavity.

Project description:Self-assembled InGaAs quantum dots (QDs) were fabricated inside a planar microcavity with two vertical cavity modes. This allowed us to excite the QDs coupled to one of the vertical cavity modes through two propagating cavity modes to study their down- and up-converted photoluminescence (PL). The up-converted PL increased continuously with the increasing temperature, reaching an intensity level comparable to that of the down-converted PL at ~120 K. This giant efficiency in the up-converted PL of InGaAs QDs was enhanced by about 2 orders of magnitude with respect to a similar structure without cavity. We tentatively explain the enhanced up-converted signal as a direct consequence of the modified spontaneous emission properties of the QDs in the microcavity, combined with the phonon absorption and emission effects.

| S-EPMC3912475 | biostudies-literature

Size Effect of Graphene Quantum Dots on Photoluminescence.

Project description:High-photoluminescence (PL) graphene quantum dots (GQDs) were synthesized by a simple one-pot hydrothermal process, then separated by dialysis bags of different molecular weights. Four separated GQDs of varying sizes were obtained and displayed different PL intensities. With the decreasing size of separated GQDs, the intensity of the emission peak becomes much stronger. Finally, the GQDs of the smallest size revealed the most energetic PL intensity in four separated GQDs. The PL energy of all the separated GQDs shifted slightly, supported by density functional theory calculations.

| S-EPMC8271461 | biostudies-literature

Thermal assisted up-conversion electroluminescence in quantum dot light emitting diodes.

Project description:Up-conversion electroluminescence, in which the energy of a emitted photon is higher than that of the excitation electron, is observed in quantum-dot light-emitting diodes. Here, we study its mechanism by investigating the effect of thermal energy on the charge injection dynamic. Based on the results of temperature-dependent electroluminescence and theoretical analysis, we reveal that at sub-bandgap voltage, holes can be successfully injected into quantum-dots via thermal-assisted thermionic-emission mechanism, thereby enabling the sub-bandgap turn-on and up-conversion electroluminescence of the devices. Further theoretical deduction and experimental results confirm that thermal-assisted hole-injection is the universal mechanism responsible for the up-conversion electroluminescence. This work uncovers the charge injection process and unlocks the sub-bandgap turn-on mechanism, which paves the road for the development of up-conversion devices with power conversion efficiency over 100%.

| S-EPMC8766545 | biostudies-literature

AgCl-doped CdSe quantum dots with near-IR photoluminescence.

Project description:We report the synthesis of colloidal CdSe quantum dots doped with a novel Ag precursor: AgCl. The addition of AgCl causes dramatic changes in the morphology of synthesized nanocrystals from spherical nanoparticles to tetrapods and finally to large ellipsoidal nanoparticles. Ellipsoidal nanoparticles possess an intensive near-IR photoluminescence ranging up to 0.9 eV (ca. 1400 nm). In this article, we explain the reasons for the formation of the ellipsoidal nanoparticles as well as the peculiarities of the process. The structure, Ag content, and optical properties of quantum dots are also investigated. The optimal conditions for maximizing both the reaction yield and IR photoluminescence quantum yield are found.

| S-EPMC5480357 | biostudies-literature

Phonon-Assisted Photoluminescence from Indirect Excitons in Monolayers of Transition-Metal Dichalcogenides.

Project description:The photoluminescence (PL) spectrum of transition-metal dichalcogenides (TMDs) shows a multitude of emission peaks below the bright exciton line, and not all of them have been explained yet. Here, we study the emission traces of phonon-assisted recombinations of indirect excitons. To this end, we develop a microscopic theory describing simultaneous exciton, phonon, and photon interaction and including consistent many-particle dephasing. We explain the drastically different PL below the bright exciton in tungsten- and molybdenum-based materials as the result of different configurations of bright and momentum-dark states. In good agreement with experiments, our calculations predict that WSe2 exhibits clearly visible low-temperature PL signals stemming from the phonon-assisted recombination of momentum-dark K-K' excitons.

| S-EPMC7307964 | biostudies-literature

Defect-induced photoluminescence blinking of single epitaxial InGaAs quantum dots.

Project description:Here we report two types of defect-induced photoluminescence (PL) blinking behaviors observed in single epitaxial InGaAs quantum dots (QDs). In the first type of PL blinking, the "off" period is caused by the trapping of hot electrons from the higher-lying excited state (absorption state) to the defect site so that its PL rise lifetime is shorter than that of the "on" period. For the "off" period in the second type of PL blinking, the electrons relax from the first excited state (emission state) into the defect site, leading to a shortened PL decay lifetime compared to that of the "on" period. This defect-induced exciton quenching in epitaxial QDs, previously demonstrated also in colloidal nanocrystals, confirms that these two important semiconductor nanostructures could share the same PL blinking mechanism.

| S-EPMC4354043 | biostudies-literature

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.

Project description:The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I-/Br-) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.

| S-EPMC5263885 | biostudies-literature

Observation of a phonon bottleneck in copper-doped colloidal quantum dots.

Project description:Hot electrons can dramatically improve the efficiency of solar cells and sensitize energetically-demanding photochemical reactions. Efficient hot electron devices have been hindered by sub-picosecond intraband cooling of hot electrons in typical semiconductors via electron-phonon scattering. Semiconductor quantum dots were predicted to exhibit a "phonon bottleneck" for hot electron relaxation as their quantum-confined electrons would couple very inefficiently to phonons. However, typical cadmium selenide dots still exhibit sub-picosecond hot electron cooling, bypassing the phonon bottleneck possibly via an Auger-like process whereby the excessive energy of the hot electron is transferred to the hole. Here we demonstrate this cooling mechanism can be suppressed in copper-doped cadmium selenide colloidal quantum dots due to femtosecond hole capturing by copper-dopants. As a result, we observe a lifetime of ~8.6 picosecond for 1Pe hot electrons which is more than 30-fold longer than that in same-sized, undoped dots (~0.25 picosecond).

| S-EPMC6778069 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data