High efficiency simple white phosphorescent organic light-emitting diodes without any charge transport layer were developed using an electron transport type high triplet energy host material. A red emitting layer/interlayer/blue emitting layer stack structure was inserted between an anode and a cathode. The electron transport type host material was used as the host for the blue emitting layer and it was mixed with a hole transport type host material in the red emitting layer. A high current efficiency of 16.2 cd/A and a maximum power efficiency of 16.5 lm/W could be obtained from the simple white device. (c) 2010 Elsevier B.V. All rights reserved.