Branched diphenylsilane derivatives containing electronically isolated indolyl moieties as host materials for blue organic light emitting diodes

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. ► New electro-active materials were synthesized and characterized. ► Thin amorphous films of the derivatives were tested as hosts in blue OLEDs. ► The best device demonstrated current efficiency of about 12 cd/A.