Boosting the performance of sky-blue fluorescent OLEDs based on DPA-containing electron-transporting materials with a V-shaped layout of triplet energy levels

Here, using a strategy called V-shaped layout of triplet energy levels (E(T)s), a high-T-1, electron-deficient and bulky 1,5-diazarcarbazole (15NCz) was first introduced for the construction of new electron-transporting materials (ETMs). When 9,10-diphenylanthracene (DPA) was encapsulated by 15NCz at different positions, a series of ETMs with high electron mobility and good thermal stability were designed and synthesized: 9-(4-(9-([1,1-biphenyl]-4-yl)anthracen-10-yl)phenyl)-9H-1,5-diazarcarbazole (p-S15NCzDPA), 9-(3-(9-([1,1-biphenyl]-3-yl)anthracen-10-yl)phenyl)-9H-1,5-diazarcarbazole (m-S15NCzDPA), 9,10-bis(4-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracene (p-D15NCzDPA) and 9,10-bis(3-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracene (m-D15NCzDPA). When these novel ETMs were used in triplet-triplet fusion (TTF) fluorescent OLEDs, they exhibited superior performance compared to devices using the common ETMs TPBi and TmPyPB. In particular, devices based on m-S15NCzDPA and m-D15NCzDPA offered a maximum luminance (L-max) of 66100 and 66950 cd m(-2), maximum current efficiency (CEmax) of 17.40 and 17.20 cd A(-1), and maximum power efficiency (PEmax) of 12.20 and 11.70 lm W-1 with a maximum external quantum efficiency (EQE(max)) of 9.00% and 8.66%, respectively. More importantly, the device based on m-D15NCzDPA also achieved lower efficiency roll-offs at high luminance (roll-offs of 2.3% and 13.9% at 10000 and 50000 cd m(-2), respectively). This work demonstrated that a V-shaped layout of E(T)s strategy was beneficial for the construction of a series of high-performance ETMs.