Blue and white light electroluminescence in a multilayer OLED using a new aluminium complex

Phenanthroimidazole derivatives showing mild intramolecular charge transfer and high quantum yields and their applications in OLEDs

Phenanthroimidazole derivatives showing bipolar characters, strong emissions in the blue region and their applications in OLED is presented.

Improvement of Quantum Dot Light Emitting Device Characteristics by CdSe/ZnS Blended with HMDS (Hexamethyldisilazane)

We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL).

TADF and exciplex emission in a xanthone-carbazole derivative and tuning of its electroluminescence with applied voltage

Materials showing white light emission have found applications in a variety of solid state devices especially in display technology. For white light emission, doping of red (R), green (G) and blue (B) emitters in a host matrix is commonly practised. However, finding RGB emitters of similar stability with homogenous doping is challenging. Furthermore, such devices suffer from color purity in the long run. Small organic light emitters, capable of colour tuning and having a broad emission spectrum are in high demand as they provide colour stability, reproducibility, a simple device geometry and high efficiency. Recently, it has been shown that the efficiency of OLEDs can be enhanced by employing thermally activated delayed fluorescence (TADF) materials. Here, we designed and synthesised a xanthone-carbazole based D-A-D material (Xan-Cbz) for TADF properties. Blue TADF emission, in neat thin films, at 470 nm was observed and further investigated by studying delayed fluorescence and lifetime measurements. In addition, a blend of Xan-Cbz with NPD shows exciplex emission at 525 nm in thin film. OLEDs based on Xan-Cbz were fabricated using several device configurations. OLEDs having the device configuration ITO/PEDOT:PSS/NPD/Xan-Cbz/Bphen/LiF-Al showed a luminance of 1.96 × 104 Cd m-2 (at a current density of 50 mA cm-2) and V ON at ∼6 V. Electroluminescence showed the features of both neat emission (470 nm) of Xan-Cbz and its exciplex (525 nm) with NPD. Further, colour tuning was observed as a function of applied voltage and the ratio of light intensity (I 525/I 470) of neat and exciplex emission was found to decrease with increasing voltage. Greenish-blue emission (CIE coordinates: 0.202, 0.382) from Xan-Cbz OLEDs was obtained. Xan-Cbz showed its neat emission (at 470 nm) in ITO/PEDOT:PSS/CBP/Xan-Cbz/Bphen/LiF-Al and pure exciplex emission (at 525 nm) in ITO/PEDOT:PSS/NPD:Xan-Cbz/Bphen/LiF-Al device configurations. Thus in this article we showed blue TADF emission, exciplex emission and voltage dependent color tuning in OLEDs based on a small organic emitter.

Si(bzimpy)2 – a hexacoordinate silicon pincer complex for electron transport and electroluminescence

We demonstrate the feasibility of hexacoordinate silicon complexes with dianionic pincer ligands as electron transport and electroluminescent components of organic electronic devices.

Electroluminescent and Optoelectronic Properties of OLEDs with Bay-Extended, Distorted Perylene Esters as Emitter Materials

Three esters with a perylene, a unilaterally, and a bilaterally extended perylene core, respectively, were used as emitter materials for organic light-emitting diodes. The electroluminescent properties of these devices were studied. Different spectral shifts were found, which can be attributed to the formation of excited dimers (excimers) in the nanofilms of the emitter materials. Thermal treatment of the unilaterally extended derivative resulted in a red-shift of the electroluminescence owing to the formation of a denser nanofilm. The luminance and efficiency of optoelectronic devices employing the extended perylene esters exceed those of devices using an emitter layer comprised of the perylene ester. Different deposition methods, limitations in the deposition process, and the role of hole-transporting materials are compared.

Chemoselective acylation of 2-amino-8-quinolinol in the generation of C2-amides or C8-esters

Chemoselective controls in acylation of 2-amino-8-quinolinol.

Effects of 2-amino-8-hydroxyquinoline interaction on the conformation of physiological isomers of human serum albumin

The methods of synthetic chemistry create small molecules rapidly for screening, and ligand-protein interaction studies provide information on how a potential drug interacts with target or carrier proteins such as serum albumin. In this work, we investigate the interaction of amino derivative of 8-hydroxyquinoline, 2-amino-8-hydroxyquinoline (A8HQ), and the effects of its binding on the conformation of different isomers of human serum albumin (HSA) using multispectroscopic techniques and molecular modeling. We found that B isomer, which exists at pH 9, bound A8HQ (K a = 1.92 ± 0.07 × 10(5) M(-1) at 298 K) more strongly as compared with N isomer (K a = 1.19 ± 0.04 × 10(5) M(-1) at 298 K) of HSA, which is known to exist around pH 6. The binding constant at physiological pH (7.4) was also determined, and the value (K a = 1.38 ± 0.05 × 10(5) M(-1) at 298 K) was found to fall between those for N and B isomers, suggesting that both the N and B isomers exist in an equilibrium in plasma. We also determined the thermodynamic parameters such as changes in enthalpy, entropy , and free energy of binding by measuring the binding at four different temperatures. Based on molecular modeling and thermodynamic studies, we propound that the A8HQ-HSA binding involves mainly hydrophobic interactions and hydrogen bonding. Site-specific marker displacement experiments and molecular modeling showed that the molecule preferably binds in subdomain IIA close to Trp214. A8HQ binding to HSA isomers was found to cause both secondary and tertiary structural alterations in the protein.