Fluorene‐Based Phosphine Oxide Host Materials for Blue Electrophosphorescence: An Effective Strategy for a High Triplet Energy Level

A bolt from the blue! Two novel host materials for blue electrophosphorescence were designed and synthesized by modification of fluorene at the 9-position with diphenylphosphine oxide to give high triplet energy levels of 2.99 eV (see scheme), achieved through an indirect linkage of the chromophore and the phosphine oxide moieties. These host materials were also found to exhibit high thermal and morphological stabilities and efficient energy transfer.