Two novel bipolar deep-blue fluorescent emitters, IP-PPI and IP-DPPI featuring different lengths of phenyl bridge, were designed and synthesized, in which imidazo[1,2-a]pyridine (IP) and phenanthroimidazole (PI) were proposed as an electron-acceptor and an electron donor respectively. Both exhibited outstanding thermal stability and high emission quantum yield. All the devices based on these two materials showed negligible efficiency roll-off with increasing current density. Impressively, non-doped organic light-emitting diodes (OLEDs) based on IP-PPI and IP-DPPI exhibited EQE of 4.85% and 4.74% with CIE coordinates of (0.153, 0.097) and (0.154, 0.114) at 10000 cd m-2, respectively. Besides, the 40 wt% IP-PPI doped device maintained high EQE of 5.23% with CIE coordinates of (0.154, 0.077) at 10000 cd m-2. The doped device based on 20 wt% IP-DPPI exhibited higher deep-blue electroluminescence (EL) performance with maximum EQE up to 6.13% at CIE of (0.153, 0.078) and remained EQE of 5.07% at 10000 cd m -2 . To the best of our knowledge, these performances are among the state-of-the art devices with CIEy ≤ 0.08 at a high brightness of 10000 cd m -2 . Furthermore, by doping a red phosphorescent dye Ir(MDQ)2 into IP-PPI and IP-DPPI hosts, high-performance red PhOLEDs with EQE of 20.8% and 19.1% were achieved, respectively. This work may provide a new approach for designing highly efficient deep-blue emitters with negligible roll-off for OLED applications.© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Imidazo[1,2-a]pyridine as an electron acceptor to construct high-performance deep-blue organic light-emitting diodes with negligible efficiency roll-off.
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