Enhancing the efficiency of simplified red phosphorescent organic light emitting diodes by exciton harvesting

► High efficiency red PHOLED is demonstrated by co-doping red and green molecules into CBP. ► The green molecule traps carriers to form excitons and transfers the energy to the red emitter. ► A maximum current efficiency of 37.0 cd/A and EQE of 24.8% have been achieved. ► The EQE remains as high as 20.8% at a high luminance of 5000 cd/m2.