High-efficiency green phosphorescent organic light-emitting diodes with double-emission layer and thick N-doped electron transport layer

•We developed high efficiency green phosphorescent organic light-emitting diode (OLED).•Our OLED had external quantum efficiency of 59.7% and power efficiency of 243 lm/W.•A double emission layer and thick n-doped electron transport layer were adopted.•High refractive index media (hemispherical lens and substrate) were also used.•We analyzed an energy loss mechanism to clarify the charge balance factor of our OLED.

We have developed green phosphorescent organic light-emitting diodes (OLEDs) with high external quantum efficiency of 59.7% and power efficiency of 243 lm/W at 2.73 V at 0.053 mA/cm2. A double emission layer and a thick n-doped electron transport layer were adopted to improve the exciton recombination factor. A high refractive index hemispherical lens was attached to a high refractive index substrate for extracting light trapped inside the substrate and the multiple-layers of OLEDs to air. Additionally, we analyzed an energy loss mechanism to clarify room for the improvement of our OLEDs including the charge balance factor.