Controlling the electronic structures of triphenylene based sky blue TADF emitters by chemical modifications for high efficiency with shorter emission lifetimes

Chemically modified triphenylene derivatives are one of the attractive candidates as an acceptor unit for realizing efficient blue thermally activated delayed fluorescence (TADF) emitters due to the rigid structure and the high triplet energy of 2.9 eV however, only a limited number of examples with low external quantum efficiency (EQE) below 10% are reported to date. Here, we developed three types of blue TADF emitters based on modified triphenylene acceptor units. These emitters showed sky blue emission with the emission peak wavelength around 470 nm, high photoluminescent quantum yield (PLQY) of ∼88%, and a short delayed lifetime (τ_d) of ∼7.7 μs. These emitters realized efficient sky blue organic light-emitting device with high EQE of over 20%.