High-performance blue OLED using multiresonance thermally activated delayed fluorescence host materials containing hetero atoms

We report three highly efficient multiresonance thermally activated delayed fluorescence blue-emitter host materials that include 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene and tetraphenylsilyl groups. The new host materials doped with the conventional v-DABNA blue emitter exhibit a high PLQY greater than 0.82, a high horizontal orientation greater than 88%, and a short PL decay time of 0.96–1.93 μs. The device with TDBA-Si shows high EQE of 36.2/35.0/31.3% at maximum luminance/500 cd m−2/1,000 cd m−2. This high performance is attributed to fast energy transfer from the host to the dopant, which is enabled by the external heavy-atom effect of Si, increased spin–orbit coupling, inhibition of aggregation by the bulky tetraphenylsilyl groups, and fast RISC of the dopant. It can also be explained by a hot triplet excited-state contribution, high thermal stability, and high horizontal orientation. We achieved a high efficiency greater than 30% and a small roll-off value of 4.9% at 1,000 cd m−2 for the first time using the newly developed TDBA-Si host material. The presentation of OLED results incorporating different heteroatoms is also scheduled.