We have designed and synthesized a blue phosphorescent host material based on a phosphine oxide moiety. 2-(diphenylphosphine oxide)-9,9'-spirobifluorene (SPPO1) was compared with N,N'-dicarbazolyl-3,5-benzene (mCP) as a blue host material in blue phosphorescent organic light-emitting diodes (PHOLEDs). The SPPO1 was effective as a host for blue PHOLEDs and the SPPO1 based blue PHOLEDs showed much higher quantum efficiency than common mCP based blue PHOLEDs. A high quantum efficiency of 16.3% and a current efficiency of 31.4 cd/A were obtained in the blue PHOLED with iridium(III) bis(4,6-(difluorophenyl)-pyridinato-N,C2') picolinate (Flrpic) as a blue phosphorescent dopant. In addition, SPPO1 was also effective as an exciton blocking material for the blue PHOLED. (C) 2009 Elsevier BM. All rights reserved.