Efficient orange-red phosphorescent organic light-emitting diodes using an in situ synthesized copper(i) complex as the emitter†
Inexpensive and eco-friendly luminescent Cu(I) complexes are ideal phosphorescent emitters for high efficiency organic light-emitting diodes (OLEDs). A series of pyrazinyl carbazole (CPz) compounds were designed and synthesized to obtain efficient luminescent Cu(I) complexes through reaction with CuI using a vacuum codeposition method. Based on photophysical studies of the CPz compounds and their codeposited CuI–CPz films, the compound 9-(3-(6-(carbazol-9-yl)pyrazin-2-yl)phenyl)-carbazole (CPzPC) with CuI was chosen as the emissive layer for OLED fabrication, where the emitter was identified as Cu2(μ-I)2(CPzPC)4 on the basis of X-ray absorption spectroscopy. After optimizing the device architecture and material selection including the CuI doping concentration and hole transporting layer, an efficient orange-red emitting OLED with a maximum emission band, an external quantum efficiency (EQE), and a luminance of 590 nm, 6.6% and 8619 cd m−2 (10 V), respectively, was achieved.