Highly Efficient White Organic Light-emitting Devices with Optimized Electron Transporting Layers

We fabricated three phosphorescent blue organic light-emitting devices based on blue phosphor of iri-dium（Ⅲ） bis[（4,6-difluorophenyl）-pyridinato-N,C2＇]（Firpic） with different electron transporting layer（ETL） materialsBy analyzing efficiency curves and spectral characteristics, the significant effect of ETL on many aspects of deviceperformance was demonstrated. With optimized ETL, the characteristics of devices, such as voltage and efficiencywere significantly improved. Combined with a yellow phosphor of iridium（Ⅲ） bis（4-phenylthieno[3,2-c]pyridinato-N,C2＇） acetylacetonate（PO-01）, phosphorescent white organic light-emitting devices（PhWOLEDs） were obtained.Then, with an aim to promote the performance of the PhWOLEDs~ a thin layer of 4,4＇,4＂-tri（N-carbazolyl）-triphenylamine（TCTA） was introduced between two light emission layers, and the diffusion of excitons was confined.The outperformance device fabricated with 4,7-diphenyl-l,10-phenanthroline（Bphen） as the electron transportinglayer exhibited a peak current efficiency of 36.6 cd/A, a peak power efficiency of 19.2 lm/W, and the InternationalCommission on Illumination coordinates（0.37, 0.46）.