Abstract
Branched diphenylsilane derivatives with pendent indolyl fragments were synthesized and characterized. The compounds show high thermal stability with thermal decomposition starting at temperatures above 367 °C and ability to form glasses with glass-transition temperatures of 53-58 °C. The electron photoemission spectra of the layers of the synthesized compounds showed ionization potentials of ca. 5.85 eV. The derivatives were tested as host materials in phosphorescent OLEDs with iridium(III)[bis(4,6-difluorophenyl)- pyridinato-N,C2′]picolinate as the guest. The device with the host derivative containing four electronically isolated indolyl fragments exhibited the best overall performance with maximum current efficiency of about 12 cd/A. © 2011 Elsevier Ltd. All rights reserved.