Alcohol-Soluble Electron-Transport Materials for Fully Solution-Processed Green PhOLEDs.

Two alcohol-soluble electron-transport materials (ETMs), diphenyl(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl) phosphine oxide (pPBlPO) 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 (1.67 x 10-4 and 2.15 x 10-4 cm2V-1 s-1), high glass-transition temperatures (81 and 110 °C), and low LUMO energy levels (-2.87 and -2.82 eV, 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 38.43 cdA-1, 26.64 lmW-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 electrontransport properties of PBIPO. [ABSTRACT FROM AUTHOR]