Two phosphorescent iridium complexes with bipolar transporting ability, namely FPPCA (500 nm) and BZQPG (600 nm), are synthesized and employed as an ideal host-guest system for phosphorescent organic light emitting diodes (PHOLEDs). The devices give very high-efficiency orange-red emission from BZQPG with maximum external quantum efficiency (EQE or eta(ext)) of >27% and maximum power efficiency (PE or eta(p)) of > 75 lm/W, and maintain high levels of 26% and 55 lm/W, 25% and 40 lm/W at high luminance of 1000 and 5000 cd m(-2), respectively, within a range of 8-15 wt% of BZQPG. The realization of such high and stable EL performance results from the coexistence of two parallel paths: i) effective energy transfer from host (FPPCA) to guest (BZQPG) and ii) direct exciton formation on the BZQPG emitter, which can alternately dominate the electrophosphorescent emission. This all-phosphor doping system removes the charge-injection barrier from the charge-transport process to the emissive layer (EML) due to the inherent narrow E-g of both phosphors. Therefore, this ideal host-guest system represents a new design to produce PHOLEDs with high efficiency and low efficiency roll-off using a simple device configuration.