OLED Applications Research Articles

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.

New luminescent tetracoordinate boron complexes: an in-depth experimental and theoretical characterisation and their application in OLEDs

New luminescent 2-iminopyrrolyl boron complexes with different BX2moieties are extensively studiedviacomplementary experimental and theoretical methodologies, including application in OLEDs.

Correction: Self-assembled blue-light emitting materials for their liquid crystalline and OLED applications: from a simple molecular design to supramolecular materials

Correction for ‘Self-assembled blue-light emitting materials for their liquid crystalline and OLED applications: from a simple molecular design to supramolecular materials’ by Vinay S. Sharma et al., Mol. Syst. Des. Eng., 2020, 5, 1691–1705, DOI: 10.1039/D0ME00117A.

A highly efficient solution and solid state ESIPT fluorophore and its OLED application

Readily accessible and functionalized ESIPT dyes with high fluorescence quantum yield in solution, including water, and in crystalline state are presented.

Photo- and electro-luminescent properties of 2,7-disubstituted spiro[fluorene-9,9′-xanthene] derivatives containing imidazole-derived moieties

Two spiro[fluorene-9,9′-xanthene]/imidazole-derived moiety hybrid compounds were synthesized for OLED applications.

Effect of different imidazole derived moieties on the photo- and electro-luminescence properties of 2,7,12-trisubstituted triazatruxene derivatives

Three 2,7,12-trisubstituted triazatruxene derivatives containing different imidazole derived moieties were synthesized for OLED applications.

Structural and optical properties of exfoliated graphene-like carbon nitride into nanosheets and quantum dots

The polymeric carbon nitride possesses the capability to form graphene like novel nanostructures (nanosheets, QDs etc) owing to its layered structure composed of tri-s-triazine units arranged in graphitic fashion by weak Vander Waals forces. Such nanostructures showed improved optoelectronic properties compared to bulk material making them potential candidates as electrode material, interface layer and active layer additive for various optoelectronic devices. Herein graphitic carbon nitride (g-C3N4) based 2D nanosheets (NS) and 0D Quantum Dots (QDs) were prepared by facile green route and acidification of bulk material respectively. Systematic structural and optical investigation were performed on the prepared nanostructures by various characterization techniques viz. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Atomic force microscopy (AFM), UV–Vis and photoluminescence (PL) to understand their structure-property relationship in details. It was observed that even after exfoliation and acidification the unit chemical structure was preserved both for NS and QDs having thicknesses nearly 3–5 nm (~ 10 layers) for NS and 0.8–1.7 nm for QDs respectively. The g-C3N4 nanostructures showed tunable band gap which increases from 2.78 eV for bulk g-C3N4 to 3.3 eV and 3.58 eV for NS and QDs respectively, as observed from the blue shifted absorption and emission spectrum. Moreover, small Urbach energy (EU) for NS (0.64 eV) and QDs (0.24 eV) and higher stokes shift of QDs compared to bulk counterpart, indicate possibilities for superior charge carrier separation and collection capabilities of such novel nanostructures, making them potential candidate for OPVs and OLEDs applications.

Solvent free and green synthesis of efficient solvochromism based coumarin moieties for quick visualization of LFPs and OLEDs applications

We report a novel solvochromism based coumarin thiophene fluorescent tags (CTFTs) namely, 3-(thiophen-2-yl)-2H-chromen-2-one (3a) and 6, 8-dichloro-3-(thiophen-2-yl)-2H-chromen-2-one (3b) via solvent free, eco-friendly, low-cost and one-pot multicomponent reaction system under microwave irradiation protocol. The synthesized CTFTs derivatives were characterized by different analytical techniques namely, Fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance spectroscopy (1H NMR), Mass spectrometer, Powder X-ray diffraction (PXRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDAX), Ultraviolet-visible (UV−vis) and Photoluminescence spectrometer (PL). The CTFTs show strong excitation peaks at 407 nm (3a) and 431 nm (3b) due to π-π* and n-π* transitions in the aromatic core and CTFTs show strong emission peaks at 456 nm (3a) and 501 nm (3b) due to σ-π* and π-π* transitions. The CTFTs derivatives exhibit cyan blue (3a) and greenish blue (3b) luminescence in liquid and solid-state. The CTFTs are investigated as an innovative category for the visualization of latent fingerprints on various non-porous material surfaces. The obtained results prove that the CTFTs can be served as promising small organic fluorescent tags for flat-panel display and latent fingerprint applications.

P‐175: Machine Learning for Mura Compensation in OLED Applications

In this paper, we present a novel Mura compensation technology by using machine learning method to dramatically reduce the DeMura processing time. Using this technology, we had successfully achieved 40% above reduction of DeMura processing time with 3.5” OLED VR display and it still can provide the same DeMura performance.

Recent Advances in Metal-TADF Emitters and Their Application in Organic Light-Emitting Diodes.

In this contribution, recent advances in new classes of efficient metal-TADF complexes, especially those of Au(I), Au(III), and W(VI), and their application in OLEDs are reviewed. The high performance (EQE = 25%) and long device operational lifetime (LT95 = 5,280 h) achieved in an OLED with tetradentate Au(III) TADF emitter reflect the competitiveness of this class of emitters for use in OLEDs with practical interest. The high EQE of 15.6% achieved in solution-processed OLED with W(VI) TADF emitter represents an alternative direction toward low-cost light-emitting materials. Finally, the design strategy of metal-TADF emitters and their next-stage development are discussed.

Yellowish-orange and red emitting quinoline-based iridium(III) complexes: Synthesis, thermal, optical and electrochemical properties and OLED application

Two novel heteroleptic iridium(III) acetylacetonate (acac) complexes K3a and K3b were synthesised from cyclometallating ligands of 2-(4′-formylphenyl)quinoline 11a and 2-(5′-formylphenyl)quinoline 11b. Complexes K3a and K3b were fully characterised by NMR spectroscopy, mass spectrometry and FT-IR. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) indicate that both complexes were amorphous solids, stable up to 303 °C and 313 °C, respectively. Complexes K3a and K3b showed strong, high-energy absorption bands (<400 nm) due to ligand-centred (1LC) transitions and weaker, low-energy absorption bands (400−600 nm) arising from a mixture of metal-to-ligand charge transfer (1MLCT/3MLCT) and ligand-centred (3LC) transitions. In degassed dichloromethane solutions, complexes K3a and K3b gave yellowish-orange and red phosphorescent emissions at 579 nm and 630 nm, with quantum efficiencies of 99.3 % and 79.3 %, respectively. At positive potential, complexes K3a and K3b exhibited a one-electron reversible oxidation (Eox1/2) peak at 0.69 V and a quasi-reversible oxidation (Eox1/2) peak at 0.60 V, respectively, which were assigned to the Ir(III)/Ir(IV) couple. At negative potentials, complexes K3a and K3b exhibited a one-electron irreversible reduction peak at -1.79 V and -1.94 V, respectively. Phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated with a device configuration of ITO/PEDOT:PSS/EML/TPBi/LiF/Al, in which K3a and K3b gave yellowish-orange and red electroluminescence (EL) at 572 nm and 628 nm, respectively. Complex K3a gave the highest luminance of 2773 cd/m2, current efficiency of 3.3 cd/A, external quantum efficiency of 1.2 % and maximum power efficiency of 1.05 lm/W with a turn-on voltage of 5.0 V (Device A).

Dioxin-annulated 1,8-naphthalimides – Synthesis, spectral and electrochemical properties, and application in OLED

A synthetic approach for preparation of a new class of 1,8-naphthalimide derivatives with fused benzo and naphtho-dioxin systems is reported. The proposed reaction conditions for the first step allow selective bromination of 1,8-naphthalic anhydride to the corresponding 3,4,6-tribromo derivative, which has the potential to be versatile building block in the chemistry of naphthalimides. The dioxin-annulated products were isolated in very good yields and their applicability for further modifications by metal-catalysed coupling reactions was proven. The synthesized fluorescent dyes showed media dependant emission and their photophysical and electroluminescent properties were evaluated with respect to their application in OLED. TGA measurements showed that all compounds are stable up to above 400 °C. The best OLED test device has turn-on voltage of 8 V; maximum luminescent intensity of 3031 cd/m2, and current efficiency of 6.9 cd/A.

Molecular deposition condition dependent structural and charge transport properties of CBP films

Optimizing organic molecular deposition conditions to improve charge transport is of great importance for applications in OLED. Based on molecular dynamics simulations, 4,4́-bis(Ncarbazolyl)-1,1́-biphenyl (CBP), a linear bipolar host OLED molecule, are deposited with different substrate temperature Tsub and inserting molecule velocity vd. It is found that in the investigated parameter range, both lower substrate temperature and higher initial velocity of inserting molecules are beneficial for obtaining more ordered morphology. Further studies based on kinetic Monte Carlo simulations reveal that the deposited structures with higher molecule order possess higher charge mobilities, which arises from the reduced energetic disorder and improved spatial correlation of site energies. It is also found that the effect of molecular ordering on electron transport is more obvious than that on hole transport. With electrical field of 1.6×105V/cm, the electron and hole mobilities can be enhanced by 100% and 42% when Tsub is increased from 200 K to 300 K (vd = 0.002 Å/fs), respectively. While their mobilities can also be enhanced by 30% and 17% with the increase of vd from 0.002 to 0.008 Å/fs (Tsub = 300 K). The larger enhancement of electron mobility can result in more balanced electron and hole mobilities in CBP, thus improve its bipolar transport characteristic. Our work not only connects the molecular morphology with charge transport properties, but also provides a strategy for improving charge mobility through the optimization of molecular deposition conditions.

Towards blue AIE/AIEE: Synthesis and Applications in OLEDs of Tetra-/Triphenylethenyl Substituted 9,9-Dimethylacridine Derivatives.

Aiming to design blue fluorescent emitters with high photoluminescence quantum yields in solid-state, nitrogen-containing heteroaromatic 9,9-dimethylacridine was refined by tetraphenylethene and triphenylethene. Six tetra-/triphenylethene-substituted 9,9-dimethylacridines were synthesized by the Buchwald-Hartwig method with relatively high yields. Showing effects of substitution patterns, all emitters demonstrated high fluorescence quantum yields of 26–53% in non-doped films and 52–88% in doped films due to the aggregation induced/enhanced emission (AIE/AIEE) phenomena. In solid-state, the emitters emitted blue (451–481 nm) without doping and deep-blue (438–445 nm) with doping while greenish-yellow emission was detected for two compounds with additionally attached cyano-groups. The ionization potentials of the derivatives were found to be in the relatively wide range of 5.43–5.81 eV since cyano-groups were used in their design. Possible applications of the emitters were demonstrated in non-doped and doped organic light-emitting diodes with up to 2.3 % external quantum efficiencies for simple fluorescent devices. In the best case, deep-blue electroluminescence with chromaticity coordinates of (0.16, 0.10) was close to blue color standard (0.14, 0.08) of the National Television System Committee.

Saturated red iridium(iii) complexes containing a unique four-membered Ir–S–C–N backbone: mild synthesis and application in OLEDs

Saturated red iridium(iii) complexes containing a four-membered Ir–S–C–N backbone were mildly prepared and applied in OLEDs.

Efficient blue, green and red iridium(iii) complexes with noncovalently-linked pyrazole/pyrazolide rings for organic light-emitting diodes

Blue, green and red iridium(iii) complexes using a new pyrazole/pyrazolide ancillary ligand system, and their application in OLEDs with EQEs of up to 21.0% and low efficiency roll-off.

AIE-active mechanoluminescent discotic liquid crystals for applications in OLEDs and bio-imaging.

A multifunctional molecular design of fluorescent discotic liquid crystal (DLC) consisting of a tetraphenylethylene core is reported, which is found to serve as an excellent solid-state emitter in OLED devices with EQE of 4.4% and tunable mechanochromism. X-ray diffraction studies unveiled that change in supramolecular self-assembly is the physical origin of mechanochromism. The luminescent DLC molecule has been shown to act as a highly selective probe for labelling acidic cellular compartments (such as lysosomes) in bio-imaging using HeLa cells.

Recent progress of narrowband TADF emitters and their applications in OLEDs

Advances in narrowband TADF emitters with a focus on the molecular design, photophysical properties and performance of the corresponding OLED devices are presented.

Self-assembled blue-light emitting materials for their liquid crystalline and OLED applications: from a simple molecular design to supramolecular materials

A new family of blue-light-emitting supramolecular bowl-shaped columnar hexagonal liquid crystals based on p-tert-butylcalix[4]arene and functionalized via chalconyl–ester-linked biphenyl amine derivatives form a self-assembly and their applications.

Tetraphenylethylene substituted thienothiophene and dithienothiophene derivatives: synthesis, optical properties and OLED applications

TPE units at the periphery of two TTs and a DTT affect the structures, properties and OLED characteristics of these three synthetically easily accessible novel conjugated compounds for materials chemistry.