Novel spironaphthalenone-based host materials for efficient red phosphorescent and thermally activated delayed fluorescent OLEDs.

Two spiro-D configured host materials DCPSO and DAPSO bearing electron-withdrawing group spironaphthalenone and electron-donating group phenylcarbazole or triphenylamine were designed and synthesized. The spironaphthalenone moiety was embedded in the host skeleton such that the host materials have twisted conformation and separated molecular frontier orbitals. The triplet energy of the DCPSO and DAPSO were estimated to be 2.60 and 2.45 eV, respectively, rendering them suitable host materials for red organic light-emitting diodes (OLEDs). The single-carrier transporting devices revealed that DCPSO is a bipolar material with more balanced hole and electron flux in the emitting layer than that of DAPSO . Employing DCPSO as host, high external quantum efficiencies of 16.6% and 13.3% as well as negligible efficiency roll-off were achieved for red phosphorescent and red TADF OLEDs. [ABSTRACT FROM AUTHOR]