서민철 교수

Highly efficient red phosphorescent dopants in organic light-emitting devices have been explored by using a cyclometalated iridium complex with a fully methylated phenyl ring and a quinoline ring as well as a sterically crowded ancillary ligand. The red phosphorescent devices with these dopants give extremely high external quantum efficiencies.

Abstract Thermally activated delayed fluorescence (TADF) is beneficial for improving the efficiency of organic light‐emitting diodes (OLEDs) by providing pathways to convert non‐emissive triplet excitons into singlet excitons. To ensure TADF is efficient, it is critical to enhance the reverse intersystem crossing (RISC) rate. To this end, most approaches propose thus far have focused on reducing the energy difference between S 1 and T 1 states. The present study explores how incorporating the in

Laser‐induced thermal imaging (LITI) has been used to pattern polymeric light‐emitting devices (see Figure). Most commercial light‐emitting polymers (LEPs) are not suitable for LITI because of strong cohesion within the LEP layer. To reduce this and achieve excellent image quality, transfer layers based on blends of LEPs and inert polymers were used. The introduction of amorphous hole‐transporting materials also enhanced the brightness of the devices.

Narrow band gaps and high electron affinities are associated with the new oligomers containing thiophene-1-oxide and thiophene-dioxide that have been prepared by zirconocene coupling methods. A series of oligomers with 3–11 rings (X=2 H, S, and S(=O)2; see picture) allow the electronic properties of conjugated chains to be investigated. Of particular note is that the less electron-withdrawing sulfoxide group results in the narrowest band gap.

To improve the viewing angle characteristic as well as the light extraction effect of strong microcavity devices, we fabricated a nanoporous polymer film (NPF) as a scattering medium as well as a light extraction component. We designed two types of organic light emitting diodes (OLEDs) with a strong microcavity effect by changing the thickness of the hole transport layer (HTL; e.g., 30 nm and 60 nm) to investigate two different scattering effects of the NPF. Very interestingly, we could observe

We report extremely high efficiency tandem white organic light-emitting diodes (OLEDs) with newly synthesized host materials. Our new host materials have well balanced bipolar characteristics and very small singlet to triplet splitting energies (∼0.4 eV) due to almost no orbital overlapping between ground and excited states. The fabricated blue phosphorescent device with one of these host materials shows very high external quantum efficiency of 25.7%, low onset and driving voltages of 2.47 V and

We have investigated a simple and cost-effective fabrication method for a porous polymer film employing the spin-coating process during continuous supply of water droplets by an ultrasonic humidifier. The resulting porous polymer film showed ∼40% optical haze, and this film could be used as a diffuser film for strong microcavity OLEDs. Specifically, we focused on controlling the surface morphology to give a three-dimensional (3D) multi-stacked nanocave structure because we had already learnt tha

A new small-molecular thermally cross-linkable material {[4-(9-phenyl-9<i>H</i>-carbazol-4-yl)phenyl]-bis-(4'-vinylbiphenyl-4-yl)-amine} (PCP-bis-VBPA, PbV) containing the styrene moiety was synthesized for hole transport layers in wet processed organic light-emitting diodes (OLEDs). It was found that PbV exhibited relatively high glass temperatures above 154 °C and a triplet energy (<i>T</i>₁) greater than 2.81 eV. This new synthetic hole transport material (HTM) forms very uniform f

A novel cross-linkable hole transport material (HTM) was used to form a robust layer structure upon continuous wet processes such as spin coating or ink-jet printing.

New soluble host materials with benzocarbazole and triphenyltriazine moieties, 11-[3-(4,6-diphenyl-[1,3,5]triazin-2-yl)-phenyl]-11H-benzo[a]carbazole and 11-[3′-(4,6-diphenyl-[1,3,5]triazin-2-yl)-biphenyl-4-yl]-11H-benzo[a]carbazole, were synthesized for highly efficient red phosphorescent organic light-emitting diodes (PHOLED). Hole-transporting benzocarbazole moiety and electron transporting triphenyltriazine moiety, which are severely twisted each other enhance the solubility of those materia

Abstract Multi‐resonant thermally activated delayed fluorescent ( MR‐TADF ) materials are blooming for high‐resolution organic light‐emitting diodes (OLEDs). However, boron/nitrogen (B/N)‐integrated MR‐TADF emitters suffer severe efficiency roll‐off from their strong inter‐molecular π – π interactions. Herein, versatile narrowband pure blue emitters ( mono‐ mx ‐CzDABNA and tri‐ mx ‐CzDABNA ) are demonstrated featuring a ring‐fused extended π ‐skeleton: a classic steric hindrance and rigidity acc