Four-Coordinate Organoboron Platforms for Efficient Red Phosphorescent Organic Light-Emitting Diodes

So far both three- and four-coordinate organoboron compounds have been widely applied in organic light-emitting diode (OLED) materials. However, the use of four-coordinate organoboron compounds as host materials is rarely reported. In this work, two new four-coordinate organoboron compounds, namely 8-(4-(9H-carbazol-9-yl)phenyl)-6,6-difluoro-6H-6λ⁴ ,7λ⁴ -benzo[4',5']imidazo[1',2':3,4][1,3,2]diazaborolo[1,5-a]pyridine (B1PCz) and 8-(3-(9H-carbazol-9-yl)phenyl)-6,6-difluoro-6H-6λ⁴ ,7λ⁴ -benzo[4',5']imidazo[1',2':3,4][1,3,2]diazaborolo[1,5-a]pyridine (B1MCz), were successfully designed, synthesized, and fully characterized. The red OLEDs using B1PCz and B1MCz as host materials achieved relatively high device performance with a maximum external quantum efficiency of 14.8 % and 11.8 %, respectively. These results will expand the scope of organoboron compounds for OLED materials and reveal the great potential of four-coordinate organoboron materials.