Highly efficient electrophosphorescent organic light-emitting diodes (PHOLEDs) containing mixed hosts of bis(3,5-di(9H-carbazol-9-yl)phenyl)diphenylsilane (SimCP2) and 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD-7) and a soluble derivative of the green emitter fac-tris(2-phenylpyridine)iridium (III) [(Ir(ppy)<sub>3</sub>] have been demonstrated. All organic layers were mixed in a single layer for solution processing during the fabrication of the PHOLEDs. The amorphous mixed host of SimCP2:OXD-7:Ir(ppy)<sub>3</sub> exhibited ambipolar charge transport as well as high hole and electron mobilities on the order of 10<sup>-7</sup> cm<sup>2</sup>/Vs from space-charge-limited current measurement. The values of both the hole and electron mobilities were 100 times greater than that of the widely used poly(9-vinylcarbazole) (PVK):OXD-7:Ir(ppy)<sub>3</sub> host, resulting in efficient charge balance in the SimCP2 host. Based on a simple fabrication process of single-layer PHOLED, a green device with the maximum luminous and power efficiencies of 42 cd/A and 20 lm/W, respectively, was obtained at 600 cd/m<sup>2</sup>.
© 2011 IEEE
Chih-Chien Lee, Chih-Hsien Yuan, Shun-Wei Liu, Li-An Liu, and Yu-San Chen, "Solution-Processed Electrophosphorescent Devices Based on Small-Molecule Mixed Hosts," J. Display Technol. 7, 636-639 (2011)