Improvement on the performance of electrophosphorescent organic light- emitting device employing n-doped bis-4,6-(3,5-di-3-pyridylphenyl)-2- methylpyrimi-dine as electron-transporting layer

摘要

The effects of using Cesium azide as an n-dopant in Bis 4,6-(3,5-di-3-pyridylphenyl)-2-methylpyrimi-dine on the performances of green phosphorescent organic light-emitting device had been studied in detail for the first time. By optimizing the device structure, phosphorescent organic light-emitting device having a maximum current efficiency of 76.4 cd/A and a maximum external quantum efficiency of 21.7% was realized. In particular, the maximum power efficiency and the power efficiency at 100 cd/m(2) were as high as 99.91m/W and 99.41m/W, respectively, which were better than the parameter on power efficiency of most reported Ir (ppy)(3)-OLEDs without out-coupling enhancement. Origins of the improvement on device characteristics in the n-doped device were systematically investigated by experimental and theoretical methods and the role of Cesium azide in enhancing the electron conductivity of the n-doped electron-transporting layer was discovered by X-ray photoelectron spectroscopy measurement.