Novel carbazole- and dioxino[2,3-b]pyrazine-based bipolar hosts for red PhOLEDs with a high brightness†
In this paper, two new bipolar host materials 7-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)benzo[5,6][1,4]dioxino[2,3-b]pyrazine (HF1) and 7-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)benzo[5,6][1,4]dioxino[2,3-b]pyrazine (HF2) are reported through introducing dioxino[2,3-b]pyrazine as the acceptor unit and carbazole as the donor unit. The two compounds exhibit excellent thermal stability and morphological stability, and have appropriate frontier orbital energy levels. Employing HF1 and HF2 as the host, the fabricated Ir(pq)2acac-based devices exhibit intrinsic red emission at 600 nm, and the maximum brightness/maximum external quantum efficiency (EQE) reaches 49 760 cd m−2/15.1% and 57 990 cd m−2/12.8% for HF1- and HF2-hosted devices, respectively. These results show that HF1 and HF2 have huge potential in organic light-emitting diode (OLED) applications.