Spiro-type host materials with rigidified skeletons for RGB phosphorescent OLEDs

摘要

A universal host material for red, green and blue phosphors raises challenges for the fabrication of efficient phosphorescent organic light-emitting diodes (PHOLEDs). Herein, two spiro host materials, namely 3-(4,6-diphenyl-1,3,5-triazin-2-yl)-9 ',9 '-dimethyl-9 ' H-spiro[fluorene-9,5 '-quinolino[3,2,1-de]acridine] (QAF-TRZ) and 3 '-(4,6-diphenyl-1,3,5-triazin-2-yl)-10-phenyl-10H-spiro[acridine-9,9 '-fluorene] (STF-TRZ), are designed and synthesized. The designed strategy is more appropriate and rarely found among the reported spiro-based skeletons for organic light-emitting diodes (OLEDs). Both materials exhibited excellent electroluminescence performance. In particular, the RGB three-color PHOLEDs based onQAF-TRZandSTF-TRZas hosts and FIrpic, Ir(ppy)(2)acac, and Ir(MDQ)(2)acac as emitters are fabricated. The blue PHOLEDs based onQAF-TRZrealize a maximum external quantum efficiency (EQE) of 19.4%, and remain 17.2% at 1000 cd m(-2). On the other hand, green PHOLEDs show maximum EQEs of 21% and 19% forQAF-TRZandSTF-TRZ, respectively, and both devices exhibit low efficiency roll-off. The red devices obtain EQEs of 22.6% and 19.4% based onQAF-TRZandSTF-TRZ, respectively, in which the former has among the most efficient value. Consequently, these results confirm that host materials incorporating the spiro-motif with sufficiently high triplet energy are promising for obtaining high performance RGB-based PHOLEDs. The better device performance based onQAF-TRZstems from its better hole transport capability, resulting in a superior charge recombination efficiency.