Efficient nondoped organic light-emitting diodes with CuI complex emitter

Abstract

In CuI complex based organic light emitting diodes (OLEDs) a host matrix is traditionally thought to be required to achieve high efficiency. Herein, it is found that the device ITO/MoO3 (1nm)/4,4′-N,N′-dicarbazole-biphenyl (CBP, 35nm)/[Cu(μ-I)dppb]2 (dppb=1,2-bis[diphenylphosphino]benzene, 20nm)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi, 65nm)/LiF (1nm)/Al (100nm) with a vacuum thermal evaporated nondoped CuI complex emissive layer (EML) showed external quantum efficiency and current efficiency of 8.0% and 24.3cd/A at a brightness of 100cd/m2, respectively, which are comparable to the maximum efficiencies reported in an optimized doped OLED with the same emitter, higher efficiency than the OLED with a [Cu(μ-I)dppb]2:CBP EML, and much higher efficiencies than the nondoped OLED with a bis(2-phenylpyridine)(acetylacetonate)iridium [Ir(ppy)2(acac)] EML. A series of reference films and single carrier devices were fabricated and studied to understand the difference between CuI and IrIII complex based nondoped OLEDs.