Thermally activated delayed fluorescence (TADF) materials are popular for achieving ultra-high-definition organic electroluminescent displays. The exciplex has the characteristic of TADF. In this work, four hosts based on meso-triarylben- zene modifications were designed and synthesized: 9-([1,1':3',1'-triphenyl]-3-yl)-9'-phenyl-9H,9'H-3,3'-bobenzogeno[3,4-b]- pyrazine (BCz-terph-ph), 9,9'-di([1,1':3',1'-triphenyl]-3-yl)-9H,9'H-3,3'-bobenzogeno[3,4-b]pyrazine (BCz-terph), 2-([1,1':3', 1'-triphenyl]-3-yl)-4-(dibenzofuran-1-yl)-6-phenyl-1,3,5-triazine (TRz-terph-dbf), and 2-(8-([1,1':3',1'-triphenyl]-3-yl)diben- zofuran-1-yl)-4,6-diphenyl-1,3,5-triazine (TRz-dbf-terph). The structures were characterized using NMR and mass spectrometry, and the thermal stability, electrochemical properties, and photophysical properties of the four molecules were tested. The four molecules formed exciplexes through physical mixing, and organic light-emitting diodes fabricated with these exciplexes as the hosts exhibited green emission in the range of 525~527 nm. Devices A1~C1 have not significant efficiency roll-off at 1000 cd•m^-2. Among them, device B1 exhibited the best performance, achieving a maximum external quantum efficiency of 19.5%.

Key words: thermally activated delayed fluorescence, meta-terphenyl, exciplex, organic light-emitting diodes