Near-infrared phosphorescent OLEDs exhibiting over 10% external quantum efficiency and extremely long lifetime using resonant energy transfer with a phosphorescent assist dopant

We have introduced a three-component light-emitting layer consisting of a host, a phosphorescent assist dopant, and a phosphorescent emitter to simultaneously realize high efficiency and long lifetime in NIR organic LEDs. An efficient energy transfer between the two phosphorescent materials was observed with 1 wt% doping ratio of the NIR emitter, significantly enhancing the external quantum efficiency reaching 10.5% with an emission peak at 769 nm. The device showed a low drive voltage and a long operational lifetime, with a luminance decay of less than 11% from the initial value after 4800 h under accelerated conditions of 100 mA cm-2.