Rubidium-carbonate-doped 4,7-diphenyl-1,10-phenanthroline electron transporting layer for high-efficiency p-i-n organic light emitting diodes

We investigated the electrical properties and charge transport mechanisms of a rubidium-carbonate (Rb2 C O3) -doped 4,7-diphenyl-1,10-phenanthroline (Bphen) electron transporting layer (ETL). The electron-only devices and photoemission spectroscopy analysis revealed that the formation of doping-induced gap states dominantly contributes to the improvement of carrier transport characteristics of the doped system. High-efficiency green phosphorescent p-doping/intrinsic/n-doping (p-i-n) organic light emitting diodes were demonstrated using the Rb2 C O3 -doped Bphen ETL and rhenium oxide (Re O3) -doped N, N′ -diphenyl- N, N′ -bis(1, 1′ -biphenyl)- 4, 4′ -diamine hole transporting layer, exhibiting an external quantum efficiency of 19.2%, power efficiency of 76 lmW, and low operation voltage of 3.6 V at 1000 cd m2.