The Optimization of Hole Injection Layer in Organic Light-Emitting Diodes

Organic light-emitting diodes (OLEDs) are widely recognized as the forefront technology for displays and lighting technology. Now, the global OLED market is nearly mature, driven by the rising demand for superior displays in smartphones. In recent years, numerous strategies have been introduced and demonstrated to optimize the hole injection layer to further enhance the efficiency of OLEDs. In this paper, different methods of optimizing the hole injection layer were elucidated, including using a suitable hole injection material to minimize the hole injection barrier and match the energy level with the emission layer, exploring new preparation methods to optimize the structure of hole injection layer, and so on. Meanwhile, this article can help people to understand the current research progress and the challenges still faced in relation to the hole injection layer in OLEDs, providing future research directions to enhance the properties of OLEDs.

Aqueous processing of organic semiconductors enabled by stable nanoparticles with built-in surfactants

The introduction of oligoether side chains onto a polymer backbone can help to stabilise polymeric dispersions in water without the necessity of surfactants or additives when conjugated polymer nanoparticles are prepared. A series of poly(3-hexylthiophene) (P3HT) derivatives with different content of a polar thiophene derivative 3-((2-methoxyethoxy)methyl)thiophene was interrogated to find the effect of the polar chains on the stability of the formed nanoparticles, as well as their structural, optical, electrochemical, and electrical properties. Findings indicated that incorporation of 10-20 percent of the polar side chain led to particles that are stable over a period of 42 days, with constant particle size and polydispersity, however the particles from the polymer with 30 percent polar side chain showed aggregation effects. The polymer dispersions showed a stronger solid-like behaviour in water with decreasing polar side chain content, while thin film deposition from water was found to afford globular morphologies and crystallites with more isotropic orientation compared to conventional solution-processed films. As a proof-of-principle, field-effect transistors were fabricated directly from the aqueous dispersions demonstrating that polymers with hydrophilic moieties can be processed in water without the requirement of surfactants.

Synthesis and optoelectronic properties of benzodithiophene-based conjugated polymers with hydrogen bonding nucleobase side chain functionality

Nucleobase functionalities in conjugated, alternating copolymers participate in interbase hydrogen bonding, which promotes molecular assembly and organization in thin films and enhances optical and electronic properties.

Synthesis of a soluble adenine-functionalized polythiophene through direct arylation polymerization and its fluorescence responsive behavior

An adenine-functionalized polythiophene is synthesized via direct arylation polymerization using Boc-protection to overcome catalyst deactivation. The resulting copolymer is highly soluble and shows reversible fluorescence quenching.

Low-Temperature Cross-Linkable Small Molecules for Fully Solution-Processed OLEDs

Cross-linkable hole-transporting, host, and electron-transporting materials with a new cross-linking group, uracil, are designed and synthesized. These compounds exhibited good solubility in common organic solvents and excellent solvent resistance after cross-linking at a low temperature of 120 °C. The OLED was fabricated by all-solution processing using cross-linkable synthetic compounds, except for the electrodes. This device exhibited a current efficiency of 39.2 cd A^-1 and a power efficiency of 15.3 lm W^-1 .

Palladium-catalyzed C–H olefination of uracils and caffeines using molecular oxygen as the sole oxidant

The palladium-catalyzed oxidative C–H olefination of uracils or caffeines with alkenes using an atmospheric pressure of molecular oxygen as the sole oxidant has been disclosed.

Supramolecular core-shell nanoparticles for photoconductive device applications

We report a breakthrough discovery involving supramolecular-based strategies to construct novel core-shell heterojunction nanoparticles with hydrophilic adenine-functionalized polythiophene (PAT) as the core and hydrophobic phenyl-C61-butyric acid methyl ester (PCBM) as the shell, which enables the conception of new functional supramolecular assemblies for constructing functional nanomaterials for applications in optoelectronic devices. The generated nanoparticles exhibit uniform spherical shape, well-controlled tuning of particle size with narrow size distributions, and excellent electrochemical stability in solution and the solid state owing to highly efficient energy transfer from PAT to PCBM. When the PAT/PCBM nanoparticles were fabricated into a photoconducting layer in an electronic device, the resulting device showed excellent electric conduction characteristics, including an electrically-tunable voltage-controlled switch, and high short-circuit current and open-circuit voltage. These observations demonstrate how the self-assembly of PAT/PCBM into specific nanostructures may help to promote efficient charge generation and transport processes, suggesting potential for a wide variety of applications as a promising candidate material for bulk heterojunction polymer devices.

Highly efficient drug delivery systems based on functional supramolecular polymers: In vitro evaluation

The novel concept of modifying and enhancing the properties of existing functional micelles through self-complementary interactions has significant potential. In this study, a practical approach to living polymerization of functionalized thermoresponsive monomers enabled the incorporation of self-constituted multiple hydrogen bonded groups into micelles that have potential as supramolecular drug-delivery systems. Phase transitions and morphological studies in aqueous solution showed that the microstructure can be controlled to achieve well-defined vesicle-like micelles with respect to the strength of the hydrogen bond segment. Thus, the resulting micelles have a very low critical micellization concentration and very high loading capacity (16.1%), making the loading process extremely stable and efficient. Incorporation of the anticancer drug doxorubicin (DOX) affected the micellization process in aqueous solution and enabled fine-tuning of drug loading and precise control of drug release rate with excellent sensitivity. Release studies in vitro showed that DOX-loaded micelles exerted dose-dependent cytotoxicity against human liver carcinoma (HepG2) cells at the physiological temperature of 37°C. In addition, DOX-loaded micelles were efficiently endocytosed by the cancer cells, which may enable the micelles to serve as suitable vehicles for effective delivery of anticancer drugs to primary tumors and metastatic disease. This newly developed material may provide a potential route towards next-generation drug delivery vehicles.

STATEMENT OF SIGNIFICANCE

A breakthrough innovation in water-based thermo-responsive polymers has enabled significant progress in developing smart stimuli-responsive nanocarriers by generating novel "supramolecular polymeric micelles" via self-complementary hydrogen-bonding interactions. These newly developed micelles exhibit extremely high micellar stability and drug loading capacity (up to 16%), excellent thermo-responsive behavior and precise control of drug release rate due to hydrogen-bond-induced physical cross-linking. In addition, doxorubicin-loaded micelles were efficiently endocytosed by the cancer cells, which allows them to serve as suitable vehicles for effective delivery of anticancer drugs to primary tumors and metastatic disease. Thus, this work provides a potential route for the development of next generation multifunctional nanocarriers that have improved safety and to increase the therapeutic efficacy of anticancer therapy.

Synthesis and fluorescence study of conjugated polymers based on 2,4,6-triphenylpyridine moieties

Three novel 2,4,6-triphenylpyridine-based conjugated polymers showed strong fluorescence emission with large Stokes' shifts, tunable band gaps and high quantum yields.

Large-scale production of ureido-cytosine based supramolecular polymers with well-controlled hierarchical nanostructures

A novel UrCy–PPG was developed for the synthesis of high-quality supramolecular polymers in large-scale production utilizing only commercially-available chemicals.

Submerged liquid plasma for the synthesis of unconventional nitrogen polymers

Glow discharge polymerization is not well understood due to the rapid/complex reaction at the plasma/gas precursor interface. Plasma reaction in a submerged condition allows post-plasma-polymerization, leading to further polymer growth and thus a stable structure. Electron collision with acetonitrile at the interface initiates the formation of radical monomers, which undergoes further rearrangement to form low-molecular (LM) nitrogen polymers (NPs). The radical-rich LM NPs go through further polymerization, forming stable high-molecular (HM) NPs (as determined using liquid chromatography/mass spectrometry). LM NPs absorb light at a wavelength of 270 nm (λ max) whereas HM NPs show absorption at 420 nm (λ max), as determined from ultraviolet-visible absorption spectra. The fluorescence spectra of HM NPs show characteristic emission at 430 nm, which indicates the presence of nitrogen functional groups with external conjugation. The proposed structure of HM NPs is verified with different analytical instruments.

Control of active semiconducting layer packing in organic thin film transistors through synthetic tailoring of dielectric materials

The influence of dielectric material's property on the solid state structure packing of active semiconducting layer in OTFTs has been carefully studied by employing a whole new family of dielectric materials based on the rigid, tetrahedral bulky moleculei.e.adamantane, a smallest cage structure of diamond.