Diphenylsilanes containing electronically isolated carbazolyl fragments as host materials for light emitting diodes

Branched derivatives containing diphenylsilane core and pendent carbazol-9-yl fragments were synthesized and characterized. The compounds represent amorphous materials of high thermal stability with glass transition temperatures of 54-93 degrees C and thermal decomposition starting at temperatures above 391 degrees C. The electron photoemission spectra of layers of the synthesized compounds showed ionization potentials of ca 5.9 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 isolated carbazolyl fragments exhibited the best overall performance with maximum current efficiency of 16.4 cd/A and maximum brightness exceeding 200 cd/m(2). (C) 2010 Elsevier B.V. All rights reserved.