Single component image of (c) InN and (d) GaN. Figure 2.13 Power-dependent PL results for InxGa1-xN. The excitation source for the PL measurement is the MIRA laser. Solution image of the rich state of the Ga complex and the enriched state of QD GaN.
General purpose of nanomaterials
Based on these different characters of the ligands, surface-tuned nanoparticles actively used for electronic applications with bioapplications. From a large surface area of nanomaterials, the colloidal nanomaterials could use both the properties of the inorganic materials and surface binding ligands.
Formation methods (top down vs. bottom up)
After the formation of the nucleation, the nuclei grew from the growth sources, which were assembled for the remaining precursors and ligands. From increasing the temperature of the solution, the precursor and ligands changed for the metal-ligand complex.
Properties of quantum dots
From the ligand exchange, the QDs could control their solvent between the hydrophobic and the hydrophilic state.3 (Fig. 1.7). From the above salient features of the QDs, the QDs were focused on next-generation photonics materials rather than organic materials, especially the luminescence fields.
About 0D materials (quantum dot, QDs) .1 History of QDs
Colloidal quantum dot synthesis method
The synthetic methods of the colloidal QDs separated for the aqueous or non-aqueous solvent conditions. As mentioned above, the hot injection and heating method is used to cause thermal decomposition of the precursor complex.
Core@shell structure & each type
For optimizing the photoemission properties of QDs, the proposed quasi-type II structure as shown in Fig. This structure consists of similar core and shell LUMO level, but the core level HOMO level is higher. level than safe.
Review of QD light emitting devices (QLED) .1 About QLED
Eco-friendly quantum dot based QLED
As presented above, InP quantum dots have shown excellent photoluminescence layers of QLEDs. Mn-doped CGS QDs.29 From Mn-doped CGS QDs used for the white light-emitting layer of QLED devices.
Pixel formation technique for realization of the QD display
II Diverse synthesis of metal nitride quantum dots and application to quantum dot light emitting devices.
Introduction .1 Metal nitride quantum dot .1 Metal nitride quantum dot
Experiment concept introduction
The QLEDs fabricated with these CQDs exhibit green electroluminescence (EL) originating from the InxGa1-xN CQDs. Our results show that InxGa1-xN CQDs are a good candidate for replacing conventional CQDs containing Cd, thereby enabling eco-friendly displays.
Results and discussion
As a result, high-quality InxGa1-xN or InxGa1-xN CQDs are more difficult to grow than Ga-rich GaN or InxGa1-xN CQDs.16-17 Therefore, the XRD results strongly suggest that it is able to grow high quality InxGa1-xN rich CQDs using our wet chemical synthetic procedure. To identify the metal composition of InxGa1-xN CQDs in detail, ICP-MS analysis was performed; the details of the analysis results are described in Fig.
M.; Walukiewicz, W.; Jeanloz, R., Red-green luminescence in indium gallium nitride alloys investigated by high pressure optical spectroscopy. J.; Sariel, J.; Chen, H.; Teraguchi, N.; Morkoç, H., Structural properties of InN films grown on GaAs substrates: observation of the zincblende polytpe. Yes, I.; Dong Song, J.; Lee, J., Temperature-dependent energy band gap variation in self-organized InAs quantum dots.
Segura-Ruiz, J.; Martínez-Criado, G.; Denker, C.; Malindretos, J.; Rizzi, A., Phase Separation in Single InxGa1–xN Nanowires Revealed by a Hard X-ray Synchrotron Nanoprobe. Ji, W.; Tian, Y.; Zeng, Q.; Qu, S.; Zhang, L.; Jing, P.; Wang, J.; Zhao, J., Efficient Quantum Dot Light-Emitting Diodes by Controlling Carrier Accumulation and Exciton Formation. Kim, Y.-K.; Won Kim, J.; Park, Y., Energy-level alignment at a charge-generating interface between 4,4[sup ʹ]-bis(N-phenyl-1-naphthylamino)biphenyl and hexaazatriphenylene-hexacarbonitrile.
Synthetic strategies of the metal nitride quantum dots for wide band gap control .1 Experiment concept introduction
Eu doped GaN quantum dot synthesis for red emitting metal nitride quantum dot realization via host-guest energy transfer
Results and discussion
Crystallinity control of GaN quantum dots for realization of the band edge emission
Results and discussion
The product of the 40 ℃ and 120 ℃ range had crystallinity, but the product of the 220 ℃ condition was composed for the polymeric complex form. The absorption results showed the first excitonic peak at a position of 340 nm, and the overdose of the ligand amount caused the blurring of the first excitonic peak. The TEM characterization shows that the synthesis of the GaN QDs occurs based on the amount of ligand.
From these results, the amine-based ligand influenced the synthesis route of GaN QDs. The XRD peak showed that GaN QDs have face-centered cubic (FCC) structured GaN. The GaCl3 complex with LiNH2 was not all converted into a polymer complex, and then the polymer complex and the GaCl3 complex with LiNH2 decomposed into GaN QDs.
GaN QDs had similar optical properties to bulk GaN materials as shown in the above results.
Results and discussion
The type of alkali metal induced the particle growth rate of Zn3N2 QDs. The thiol ligand is used to optimize the synthesis route of Zn3N2 QDs as shown in Fig. From this trend, the thiol ligand is needed for the stable mass production of Zn3N2 QDs.
To optimize the state of the alloy, Ga oleate, GaCl3 and GaI3 were used as Ga precursors. The particle size of the ZnxGa1-xN QDs was in the range of 7~9 nm, and the particle shape was assembled for a spherical shape. Zn/Ga : 0.2) Particle size and shape did not affect the type of Ga precursors as shown in TEM images.
Schematic illustration of the oxidation mechanism of Zn3N2 QDs by residual methanol H2O.
Ligand Assisted Post Treatment for Efficient CsPbX 3 Perovskite Quantum Dot Light Emitting Devices
- Experiment concept introduction
- Results and discussion
- Conclusion
- References
The hole injection layer adaptation used from perfluorinated ionomer (PFI) treatment at poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine) (poly-TPD) layer for vacuum level control of poly- TPD layer for reducing hole injection barrier of CsPbX3 PeQDs photoemission layer.14 The cross-linking via trimethylammonium (TMA) vapor deposition at CsPbX3 PeQDs layer applied for surface passivation with film coating improvement.15 From surface passivation via cross-linking, the external quantum efficiency of red state PeQDs has 5.7 % shown from the increase of the PL-QY of red state (90 %) with film coating improvement. For the optimization of electrical properties, we used poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-ioctyl- fluorene) applied ) (PFN) as bipolar polyelectrolyte for reducing electron injection barrier of PeQDs layer. From PFN treatment, we proposed unitary device structure for different band gap conditions from the minimization of electron injection barrier.
From PFN thickness increasing, the electron injection barrier of PeQDs decreased by vacuum level shift. This tendency of vacuum level shift of PeQDs provided opportunity for electron and hole injection balance control from injection barrier control as shown in Fig. For PeQLED performance optimization, we approached surface defect reduction with electron injection barrier of photoemissive layer of LAPT with PFN treatment.
Reducing the turn-on voltage indicated a reduction in the electron injection barrier due to vacuum level shift, as shown in the UPS results.
High performance CsPbX 3 perovskite quantum dot light emitting devices achieved via solid-state ligand exchange
Introduction
To solve this, short-chain ligand exchange methods are used to develop conventional QD solar cells, in terms of reducing the resistance of the photoactive layer.19,20,21 However, the use of this method for PeQDs is quite challenging, because the original capping ligands on PeQDs are relatively unstable and the stability of PeQDs is very low during the ligand exchange reaction, which results in the poor photoemission properties of PeQDs. To maintain the photoemission property of the purified PeQDs, some excess ligands are required to improve the adsorption rate of the surface ligands. However, these excess ligands improve the insulating properties of PeQD films which are produced with ligand-rich PeQD dispersions.
Conventional solid-state ligand exchange (SLE) methods involve dripping a solution of short-chain ligands in a QD antisolvent onto the surface of a QD film. 21 However, it is difficult to apply the traditional SLE method to CsPbX3 PeQDs layers because they are prone to degradation when in direct contact with hydrophilic antisolvents such as alcohols. First, due to the solubility control between the ligand and the solvent, the PL quenching of PeQDs was well suppressed due to the prevention of the loss of surface-bound ligands. Second, from the optimized combinations of ligand and solvent, a more suitable SLE processing method for PeQDs film could be developed without the use of an antisolvent.
This strategy is also favorable because the stability of the PeQDs layer can be significantly improved.
Results and discussion
3.12(e) shows the peak at 1395 cm-1 corresponding to the C=C vibration after the introduction of the aromatic ligand. The results confirm that the peaks become stronger as the ratio of the short-chain ligand increases. 3.13 (b) shows comparative results according to the types of short-chain ligands before and after vacuum treatment in a vacuum chamber.
3.13(c) shows the changes in relative PL intensity according to the ratio of short-chain ligand. The aim of this analysis was to investigate the change in exciton lifetime according to the passivation ratio of the short-chain ligands. As the ligand concentration in the SLE solution increased, the passivation ratio of the short-chain ligand increased.
These results suggest that controlling the surface defect level (controlling the photoemission property) of the active layer directly affects the photoemission property of the PeQLED.
Conclusion
A stock solution of the cesium-surfactant complex was prepared by mixing cesium carbonate (5 mmol), oleic acid (16 mmol) and stearic acid (8 mmol) in 1-octadecene (ODE, 8 mL) under vacuum with vigorous reaction mixing and heating to 120 ° C. The resulting crude mixture was purified by centrifugation with an excess of the anti-solvent, and precipitation. The resulting solutions of the short-chain ligands were spun on the PeQD films at 2000 rpm under an inert atmosphere in the glove box.
A TCSPC module (Pico-quant, FluoTime 300) was used for the ultrafast measurement of the PL decay. The deconvolution of the actual fluorescence decay and the IRF was performed using curve fitting software (FlouFit, Pico-Quant) to determine the time constant associated with each of the observed exponential decays. Finally, 11 nm thick LiF and 100 nm thick Al layers were successively thermally evaporated on top of the TPBi layer to serve as a cathode.
The current–voltage–luminance characteristics of the PeQD LED were measured using a Keithley 2400 source meter and a luminance meter (Minolta, CS-100A).
As the initial step, the Eu metal insertion was applied for the utilization of the host-guest energy transfer. Because the Eu metal alloy served a slight enhancement of the crystallinity of the host material (GaN). For fine-tuning the band gap for red-emitting metal nitride QDs, the Zn- and Ga-based nitride QDs have been developed.
For these reasons, it chooses Zn-based metal nitride semiconductor as the candidate for next-generation QDs material. The thiol-based soft ligand also attempted to stabilize the Zn-based metal nitride QDs synthesis. At the same time, synthesis of the perovskite QDs and their surface treatment was attempted to optimize the optoelectronic properties.
For the development of the surface treatment of perovskite QDs, CsPbX3 PeQDs have been chosen as a model system.
