Zhu Mei-Xiang

Synthesis and photophysical and electrochemical properties of new cyclometalated platinum complex containing oxadiazole ligand

A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated. A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry (CV) analysis shows that the EHOMO (energy level of the highest occupied molecular orbital) and EHOMO (energy level of the lowest unoccupied molecular orbital) of the platinum complex are about −5.69 and −3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.

Improved Blue-Green Electrophosphorescence from a Tuning Iridium Complex with Benzyl Group in Polymer Light-Emitting Devices

Electroluminescence performances from a tuning biscyclometlated iridium complex with benzyl group are demonstrated in double-layered polymer light-emitting devices (PLEDs) using a blend of poly(9,9-dioctylfluorene) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix. Blue-green electrophosphorescent emission with a peak at 521 nm and a shoulder at 492 nm was observed. The highest luminance efficiency of 4.8 cd/A at current density of 0.56mA/cm2 and a maximum luminance of 1944cd/m2 at 217.6 mA/cm2 were achieved in the devices at the dopant concentration of 8%. The luminous performance of the devices becomes better with increasing dopant concentrations from 1% to 8%. This implies that the concentration quenching of this iridium complex with benzyl group can be efficiently inhibited in the devices.

Enhanced Green Electrophosphorescence from Oxadiazole-Functionalized Iridium Complex-Doped Devices Using Poly(9,9-Dioctylfluorene) Instead of Poly(N-Vinylcarbazole) as a Host Matrix

Optoelectronic properties of the oxadiazole-functionalized iridium complex-doped polymer light-emitting devices (PLEDs) are demonstrated with two different polymeric host matrices at the dopant concentrations 1–8%. The devices using a blend of poly(9,9-dioctylfluorene)(PFO) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as a host matrix exhibited a maximum luminance efficiency of 11.3 cd/A at 17.6 mA/cm2. In contrast, the devices using a blend of poly(N-vinylcarbazole) (PVK) and PBD as a host matrix reveal only a peak luminance efficiency of 6.5 cd/A at 4.1 mA/cm2. The significantly enhanced electrophosphorescent emissions are observed in the devices with the PFO-PBD blend as a host matrix. This indicates that choice of polymers in the host matrices is crucial to achieve highly efficient phosphorescent dye-doped PLEDs.

Red Electrophosphorescence from Oxadiazoles-Functionalized Iridium Complexes in Polymer Light-Emitting Devices

A type of oxadiazole-functionalized iridium complex is newly employed as red phosphor emitter in polymer light-emitting devices (PLEDs) using a blend of poly (9,9-dioctylfluorene)(PFO) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) as a host matrix. The devices show bright red electrophosphorescence with dominant peaks at about 593 nm and shoulders at about 642 nm. The highest luminance efficiency of 3.3 cd/A at 9.3 V and maximum luminance of 2912 cd/m2 at 14.0 V are achieved in the devices. At current density of 100 mA/cm2, the devices still exhibit luminance efficiency of 2.2 cd/A and luminance of 2300 cd/m2. This indicates that the oxadiazole-functionalized iridium complexes have improved optoelectronic properties in the devices at high current density.