Electrical and optical characteristics of phosphorescent organic light-emitting device with thin-codoped layer insertion

In this paper, we demonstrated the changes of electrical and optical characteristics of a phosphorescent organic light-emitting device (OLED) with tris(phenylpyridine)iridium Ir(ppy)(3) thin layer (4 nm) slightly codoped (1%) inside the emitting layer (EML) close to the cathode side. Such a thin layer helped for electron injection and transport from the electron transporting layer into the EML, which reduced the driving voltage (0.40 V at 100 mA/cm(2)). Electroluminescence (EL) spectral shift at different driving voltage was observed in our blue OLED with [(4,6-di-fluoropheny)-pyridinato-N,C-2']picolinate (FIrpic) emitter, which came from the recombination zone shift. With the incorporation of thin-codoped Ir(ppy)(3), such EL spectral shift was almost undetectable (color coordinate shift (0.000, 0.001) from 100 to 10,000 cd/m(2)), due to the compensation of Ir(ppy)(3) emission at low driving voltage. Such a methodology can be applied to a white OLED which stabilized the EL spectrum and the color coordinates ((0.012, 0.002) from 100 to 10,000 cd/m(2)). (C) 2015 Elsevier B.V. All rights reserved.