Browse
Submit Data
Databases
API
Help

Dataset Information

26 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Green Light-Emitting Devices Based on Perovskite CsPbBr₃ Quantum Dots.

ABSTRACT: In this paper, high quality green-emitting CsPbBr₃ quantum dots (QDs) are successfully synthesized by hot-injection method. Different injection temperatures are tested to optimize the synthesis conditions. High brightness with the photoluminescence (PL) quantum yields (QYs) up to 90% and narrow size-distribution with the full width at half-maximum (FWHM) of 18.5 nm are obtained under the optimized conditions. Green light emitting diodes (LEDs) based on the CsPbBr₃ QDs are successfully demonstrated by combining solution method with vapor deposition method. Composite films of poly[9,9-dioctylfluorene-co- N-[4-(3-methylpropyl)]-diphenylamine] (TFB) and bathocuproine (BCP) layers are chosen as the hole-transporting and the electron-transporting layers, respectively. The highly bright green QD-based light-emitting devices (QLEDs) showing maximum luminance up to 46,000 cd/m² with a low turn on voltage of 2.3 V, and peak external quantum efficiency (EQE) of 5.7%, corresponding to 19.9 cd/A in luminance efficiency. These devices also show high color purity for electroluminescence (EL) with FWHM <20 nm, and no redshift and broadening with increasing voltage as well as a spectral match between PL and EL.

SUBMITTER: Yu H

PROVIDER: S-EPMC6151352 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Fabrication of Thin Films from Powdered Cesium Lead Bromide (CsPbBr3) Perovskite Quantum Dots for Coherent Green Light Emission.

Project description:High-quality thin films were obtained directly by spin-coating glass substrates with suspensions of powdered cesium lead bromide (CsPbBr3) perovskite quantum dots (PQDs). The structural properties of the films were characterized via transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). The crystal structure of the CsPbBr3 PQDs was unique. The optical behavior of the CsPbBr3 PQDs, including absorption and emission, was then investigated to determine the absorption coefficient and band gap of the material. The CsPbBr3 PQDs were evaluated as active lasing media and irradiated with a pulsed laser under ambient conditions. The PQDs were laser-active when subjected to optical pumping for pulse durations of 70-80 ps at 15 Hz. Amplified spontaneous emission (ASE) by the CsPbBr3 PQD thin films was observed, and a narrow ASE band (∼5 nm) was generated at a low threshold energy of 22.25 μJ cm-2. The estimated ASE threshold carrier density (n th) was ∼7.06 × 1018 cm-3. Band-gap renormalization (BGR) was indicated by an ASE red shift and a BGR constant of ∼27.10 × 10-8 eV. A large optical absorption coefficient, photoluminescence (PL), and a substantial optical gain indicated that the CsPbBr3 PQD thin films could be embedded in a wide variety of cavity resonators to fabricate unique on-chip coherent light sources.

| S-EPMC7689956 | biostudies-literature

CsPbBr3/CdS Core/Shell Structure Quantum Dots for Inverted Light-Emitting Diodes Application.

Project description:Novel CsPbBr3/CdS core/shell structure quantum dots (QDs) were successfully synthesized using a facile hot-injection method. The corresponding CsPbBr3/CdS QDs based light-emitting diodes (QLEDs) were further prepared, which demonstrated the maximum luminance of 354 cd/m2 and an external quantum efficiency (EQE) of 0.4% with the current efficiency (CE) of 0.3 cd/A. Moreover, the optoelectronic performance of the CsPbBr3/CdS QDs based QLEDs exhibited a comparable enhancement in contrast to the pure CsPbBr3 QDs based QLEDs. Hypothetically, the novel CsPbBr3/CdS structure QDs introduced one new route for advanced light emission applications of perovskite materials.

| S-EPMC6640208 | biostudies-literature

Intermittency of CsPbBr3 Perovskite Quantum Dots Analyzed by an Unbiased Statistical Analysis.

Project description:We analyze intermittency in intensity and fluorescence lifetime of CsPbBr3 perovskite quantum dots by applying unbiased Bayesian inference analysis methods. We apply change-point analysis (CPA) and a Bayesian state clustering algorithm to determine the timing of switching events and the number of states between which switching occurs in a statistically unbiased manner, which we have benchmarked particularly to apply to highly multistate emitters. We conclude that perovskite quantum dots display a plethora of gray states in which brightness, broadly speaking, correlates inversely with decay rate, confirming the multiple recombination centers model. We leverage the CPA partitioning analysis to examine aging and memory effects. We find that dots tend to return to the bright state before jumping to a dim state and that when choosing a dim state, they tend to explore the entire set of states available.

| S-EPMC8282187 | biostudies-literature

Double-Shelled InP/ZnMnS/ZnS Quantum Dots for Light-Emitting Devices.

Project description:Traditionally, ZnS or ZnSe is chosen as the shell material for InP quantum dots (QDs). However, for green or blue InP QDs, the ZnSe shell will form a type-II structure resulting in a redshift of the emission spectrum. Although the band gap of ZnS is wider, its lattice mismatch with InP is larger (∼7.7%), resulting in more defect states and lowered quantum yield (QY). To overcome the above problems, we introduced the intermediate ZnMnS layer in InP/ZnMnS/ZnS QDs. The wide band gap of the intermediate layer (3.7 eV) can confine the electrons and holes in the core completely, and the formation of the type-II structure is avoided. As a result, green InP-based QDs with QY up to 80% were obtained. By adjusting the halogen ratios of the ZnX2 precursor, the minimum and maximum emission peaks are 470 and 620 nm, respectively, covering the whole visible range. Finally, after optimizing the coating shell process, the maximum external quantum efficiency of QD light-emitting diodes fabricated from this InP-based green light QDs can reach 2.7%.

| S-EPMC6868586 | biostudies-literature

Concurrent Ultrafast Electron- and Hole-Transfer Dynamics in CsPbBr3 Perovskite and Quantum Dots.

Project description:Ultrafast charge-transfer (i.e., electron and hole) dynamics has been investigated between the cesium lead bromide (CsPbBr3, CPB) perovskite nanocrystals (NCs) and cadmium selenide (CdSe) quantum dots (QDs) as a new composite material for photocatalytic and photovoltaic applications. The CPB NCs have been synthesized and characterized by high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) pattern. The redox levels (i.e., conduction band (CB) and valence band (VB)) of the CPB NCs and CdSe QDs suggest the feasibility of photoexcited electron transfer from CPB NCs to CdSe QDs and photoexcited hole transfer from CdSe QDs to CPB NCs, and it has been confirmed by both steady-state and time-resolved spectroscopy. To investigate the electron- and hole-transfer dynamics in ultrafast time scale, we have performed femtosecond up-conversion and femtosecond transient absorption studies. The measured electron-transfer time from CPB NCs to CdSe QDs and hole-transfer time from CdSe QDs to CPB NCs were found to be 550 and 750 fs, respectively. Interestingly, the charge-transfer process found to be restricted in CPB/CdSe@CdS core-shell system where electron transfer from CPB NCs to core shell takes place, but the hole transfer from core shell to CPB NCs found to be restricted due to CdS shell making the process thermodynamically nonviable. Our observation has suggested that after the photoexcitation of CPB NCs/CdSe QDs composite system, a charge-separated state is formed where the electrons are localized in CB of CdSe QDs and holes are localized in VB of CPB NCs. This makes the composite system a better material for efficient light harvesting and photocatalytic material as compared to the individual ones.

| S-EPMC6641258 | biostudies-literature

Rapid Crystallization of All-Inorganic CsPbBr3 Perovskite for High-Brightness Light-Emitting Diodes.

Project description:Research into perovskite-based light-emitting diodes (PeLEDs) has been rapidly gaining momentum since the initial reports of green-emitting methylammonium lead bromide (CH3NH3PbBr3)-based devices were published. However, issues pertaining to its stability and morphological control still hamper progress toward high performing devices. Solvent engineering, a technique typically employed to modulate film crystallization, offers little opportunity for scale-up due to the tendency for inhomogeneous film growth and low degree of reproducibility. Here, we propose and show a simple gas-facilitated process to deposit a stable, all-inorganic perovskite CsPbBr3 film. The formation of smaller and less percolated grains, which gives rise to enhanced optical properties, highlights the importance of spatial charge confinement in the film. Consequently, the performance of our PeLEDs shows great improvement, with luminance as high as 8218 cd m-2 and turn-on voltage as low as 2.4 V. Concomitantly, the current efficiency and EQE of our device were increased to 0.72 cd A-1 and 0.088%, respectively. High reproducibility in the performance of PeLEDs fabricated using this process opens the path for large-area devices.

| S-EPMC6640975 | biostudies-literature

Efficient exciton generation in atomic passivated CdSe/ZnS quantum dots light-emitting devices.

Project description:We demonstrate the first-ever surface modification of green CdSe/ZnS quantum dots (QDs) using bromide anions (Br-) in cetyl trimethylammonium bromide (CTAB). The Br- ions reduced the interparticle spacing between the QDs and induced an effective charge balance in QD light-emitting devices (QLEDs). The fabricated QLEDs exhibited efficient charge injection because of the reduced emission quenching effect and their enhanced thin film morphology. As a result, they exhibited a maximum luminance of 71,000?cd/m2 and an external current efficiency of 6.4?cd/A, both significantly better than those of their counterparts with oleic acid surface ligands. In addition, the lifetime of the Br- treated QD based QLEDs is significantly improved due to ionic passivation at the QDs surface.

| S-EPMC5043346 | biostudies-literature

Top-emitting quantum dots light-emitting devices employing microcontact printing with electricfield-independent emission.

Project description:Recent breakthroughs in quantum dot light-emitting devices (QD-LEDs) show their promise in the development of next-generation displays. However, the QD-LED with conventional ITO-based bottom emission structure is difficult to realize the high aperture ratio, electricfield-independent emission and flexible full-color displays. Hence, we demonstrate top-emitting QD-LEDs with dry microcontact printing quantum dot films. The top-emitting structure is proved to be able to accelerate the excitons radiative transition rate, then contributing to stable electroluminescent efficiency with a very low roll-off, and preventing spectra from shifting and broadening with the electric field increases. The results suggest potential routes towards creating high aperture ratio, wide color gamut, color-stable and flexible QD-LED displays.

| S-EPMC4773764 | biostudies-other

High Color-Purity Green, Orange, and Red Light-Emitting Diodes Based on Chemically Functionalized Graphene Quantum Dots.

Project description:Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47?cd A(-1) and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color.

| S-EPMC4822170 | biostudies-literature

Stable Hexylphosphonate-Capped Blue-Emitting Quantum-Confined CsPbBr3 Nanoplatelets.

Project description:Quantum-confined CsPbBr3 nanoplatelets (NPLs) are extremely promising for use in low-cost blue light-emitting diodes, but their tendency to coalesce in both solution and film form, particularly under operating device conditions with injected charge-carriers, is hindering their adoption. We show that employing a short hexyl-phosphonate ligand (C6H15O3P) in a heat-up colloidal approach for pure, blue-emitting quantum-confined CsPbBr3 NPLs significantly suppresses these coalescence phenomena compared to particles capped with the typical oleyammonium ligands. The phosphonate-passivated NPL thin films exhibit photoluminescence quantum yields of ∼40% at 450 nm with exceptional ambient and thermal stability. The color purity is preserved even under continuous photoexcitation of carriers equivalent to LED current densities of ∼3.5 A/cm2. 13C, 133Cs, and 31P solid-state MAS NMR reveal the presence of phosphonate on the surface. Density functional theory calculations suggest that the enhanced stability is due to the stronger binding affinity of the phosphonate ligand compared to the ammonium ligand.

| S-EPMC7296617 | biostudies-literature