Effect of the molecular structure of the host materials on the lifetime of green thermally activated delayed fluorescent organic light-emitting diodes

Two dibenzothiophene derived compounds, 4-(3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene (DBTTP1) and 4-(5'-phenyl-[1,1':3',1 ''-terphenyl]-3-yl)dibenzo[b,d]thiophene (DBTTP2), were prepared as the host materials for green thermally activated delayed fluorescent (TADF) emitters to investigate the effect of the molecular structure of the host materials on the efficiency and lifetime of the green TADF devices. The green TADF devices fabricated using the DBTTP1 host material exhibited a high quantum efficiency of above 20% and a lifetime longer than 250 h up to 80% of initial luminance at 1000 cd m(-2). Comparing the two host materials, triphenylene modified DBTTP1 was better than terphenyl modified DBTTP2 in terms of the lifetime of the green TADF devices.