Two alcohol-soluble electron-transport materials (ETMs), diphenyl(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)phosphine oxide (pPBIPO) and (3,5-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)diphenylphosphine oxide (mBPBIPO), have been synthesized. The physical properties of these ETMs were investigated and they both exhibited high electron-transport mobilities (1.67x10(-4) and 2.15x10(-4)cm(2)V(-1)s(-1)), high glass-transition temperatures (81 and 110 degrees C), and low LUMO energy levels (-2.87 and -2.82eV, respectively). The solubility of PBIPO in n-butyl alcohol was more than 20mgmL(-1), which meets the requirement for fully solution-processed organic light-emitting diodes (OLEDs). Fully solution-processed green-phosphorescent OLEDs were fabricated by using alcohol-soluble PBIPO as electron-transport layers (ETLs), and they exhibited high current efficiencies, power efficiencies, and external quantum efficiencies of up to 38.43cdA(-1), 26.64lmW(-1), and 10.87%, respectively. Compared with devices that did not contain PBIPO as an ETM, the performance of these devices was much improved, which indicated the excellent electron-transport properties of PBIPO.