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 °C and thermal decomposition starting at temperatures above 391 °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/m2.