Synthesis of a Novel Blue- light- emitting Polymer Material Bearing Coumarin Pendants

A novel blue luminescent polymer bearing coumarin pendants was prepared. Its luminescent properties were determined indicating that it had strong blue fluorescent properties and good film formation ability. This novel polymer can be used as a blue organic electroluminescent material (OELM) in organic electroluminescent devices.

Synthesis of Pyrazolines Used as Blue Organic Electroluminescence Materials

Three kinds of pyrazolines were designed and synthesized. Their structures were elucidated by IR, (HNMR)-H-1, MS, UV and elemental analysis. Their luminescent properties were determined, which indicated that they had strong blue fluorescent properties. One of them was designed to have good film formation. All the three kinds of pyrazolines can be used as blue organic electroluminescence materials (OELMs).

A Stable Blue Organic Electroluminescent Material

In order to compare two kinds of blue electroluminescent materials, we have investigated two kinds of blue OLEDs with the similar structrue ITO/CuPc/NPB/JBEM: perylene/Alq/Mg:Ag [device(J)] and ITO/CuPc/NPB/DPVBi: perylene/Alq/Mg:Ag [device(D)]. The difference of luminance and efficiency was not obvious for the two devices. However, there was remarkable difference for their lifetime. The device(J) achieved longer half lifetime of 1035 h at initial luminance of 100 cd/m 2, and that of device(D) was only 255 h. According to their energy level diagrams , the difference of their stability may originate from different host materials in the two devices. It may be attributed to the better thermal stability of JBEM molecules than that of DPVBi. It is shown that JBEM may be a promising blue organic electroluminescent material with great stability.

A New Distyrylarylene Derivative Used as Blue Light Emitter in Organic Electroluminescent Device

A new blue electroluminescent material, distyrylarylene(DSA) derivative, 4,4' bis[2,2 (1 naphthyl,phenyl)vinyl] 1,1' biphenyl(NPVBi) is designed and synthesized. The DSA derivative shows better thermal stability because of its high glass transition temperature. A blue organic light emitting diode(OLED) with the structure ITO/TPD/NPVBi/Alq/LiF/Al is studied. The electroluminescent(EL) spectrum of the OLED exhibits that light emission originates from NPVBi with a peak at 460 nm, its Commission Internationale de l'Eclairage(CIE) color coordinates are x=0.16, y=0.15, and showing independence of CIE color coordinates on current density. The new DSA derivative is expectable as a new candidate for blue light emitter in OLEDs.

Towards Efficient Blue DelayedFluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Constructing blue thermally activated delayedfluorescence materials for high-performance organic light-emitting diodes(OLEDs)remains challenging due to the intrinsically strong intramolecular charge transfer nature of the nearly orthogonal connection of electron donor(D)and acceptor(A),which results in long-wavelength emission.Herein,an effective delayed-fluorescence design strategy of modulating D–A torsion angles is proposed and efficient sky-blue,pure-blue,and deep-blue delayed-fluorescence molecules consisting of a xanthenone acceptor and carbazole-based donors are created by decreasing the torsion angles.They exhibit strong delayed fluorescence with high photoluminescence quantum yields of 85–94%in doped films,and their delayed-fluorescence lifetimes are elongated from 1.0 to 27.6μs as the torsion angles decrease.These molecules can function as excellent emitters in OLEDs,providing efficient electroluminescence peaking at 442 nm(CIEx,y=0.15,0.08),462 nm(CIEx,y=0.15,0.18),and 482 nm(CIEx,y=0.17,0.30)with state-of-the-art external quantum efficiencies of up to 22.2%,33.7%,and 32.1%,respectively,demonstrating the proposed molecular design for efficient blue delayed-fluorescence molecules is successful and promising.