Novel spiro-based host materials for application in blue and white phosphorescent organic light-emitting diodes

• Two novel spirobifluorene hosts were designed with high triplet energy.
• Both materials showed high glass transition temperatures over 150 °C.
• The FIrpic based PHOLEDs hosted by SF3Cz1 and SF3Cz2 exhibited high EQEs of 18.1% and 19.7% respectively.
• Two-color warm white PHOLEDs hosted by SF3Cz1 and SF3Cz2 also achieved high EQEs and low efficiency roll-offs.

Two novel spiro-based host materials, namely 3-(9,9′-spirobi[fluoren]-6-yl)-9-phenyl-9H-carbazole (SF3Cz1) and 9-(3-(9,9′-spirobi[fluoren]-6-yl)phenyl)-9H-carbazole (SF3Cz2) were designed and synthesized. Due to the meta-linkage of spirobifluorene backbone, both SF3Cz1 and SF3Cz2 possess triplet energies over 2.70 eV, indicating they could serve as suitable hosts for blue and even white phosphorescent organic light-emitting diodes (PHOLEDs). The fabricated bis(4,6-(difluorophenyl)-pyridinato -N,C′)picolinate (FIrpic) based PHOLEDs hosted by SF3Cz1 and SF3Cz2 exhibited excellent performance with maximum external quantum efficiencies (EQEs) of 18.1% and 19.7%, respectively. Two-color warm white PHOLEDs fabricated by utilizing SF3Cz1 and SF3Cz2 as hosts also achieved high EQEs and low efficiency roll-offs. The results demonstrate that SF3Cz1 and SF3Cz2 are promising hosts for blue and white PHOLEDs.

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