A series of ultrapure-blue thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) have been constructed by close stacking between the donor and acceptor moieties in rigid heteroaromatic compounds. The obviously accelerated radiative transition of singlet excitons, the diminished vibrionic relaxation of ground and excited states, and the consequent reduced Stokes shift and the narrow emission are evident. The corresponding organic light-emitting diodes (OLEDs) based on AC-BO realize the best performance among all deep-blue TSCT-TADF emitters, with an external quantum efficiency (EQE max ) of 19.3 %. Furthermore, the OLEDs based on QAC-BO display an EQE max of 15.8 %, and achieve the first high-efficiency ultrapureblue TSCT-TADF material with an excellent Commission Internationale de L'Eclairage coordinate (CIE) of (0.145, 0.076) which perfectly matches the ultrapureblue CIE requirements (0.14, 0.08) defined by the National Television System Committee.
Thermally activated delayed fluorescence (TADF) materials have attracted extensive attention because of their 100% theoretical exciton utilization. Solution‐processable orange‐red TADF polymers are one of indispensable participants. Herein, a series of orange‐red TADF polymers with dibenzothiophene (DBT) and carbazole (Cz) units as joint backbones are synthesized. Their performance can be successfully optimized by regulating the connection positions of DBT units through backbone engineering. It is found that the pNAI37 series with DBT units embedded in the polymeric backbones at the 3, 7 sites display a better performance than those connected at the 2, 8 sites. The optimal polymer, pNAI3705, exhibits a better excited state nature, leading to the photoluminescence quantum yield of 60%. Consequently, pNAI3705 based organic light‐emitting diodes reach a maximum external quantum efficiency of 20.16%, and maintain 10.61% at 500 cd m−2, which is in first tier among orange‐red polymers. These results unambiguously suggest the potential application of the combined DBT and Cz backbones in TADF polymers. This design strategy may provide a versatile approach for optimizing the properties of TADF polymers through backbone engineering.
A series of ultrapure-blue thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) have been constructed by close stacking between the donor and acceptor moieties in rigid heteroaromatic compounds. The obviously accelerated radiative transition of singlet excitons, the diminished vibrionic relaxation of ground and excited states, and the consequent reduced Stokes shift and the narrow emission are evident. The corresponding organic light-emitting diodes (OLEDs) based on AC-BO realize the best performance among all deep-blue TSCT-TADF emitters, with an external quantum efficiency (EQE max ) of 19.3 %. Furthermore, the OLEDs based on QAC-BO display an EQE max of 15.8 %, and achieve the first high-efficiency ultrapureblue TSCT-TADF material with an excellent Commission Internationale de L'Eclairage coordinate (CIE) of (0.145, 0.076) which perfectly matches the ultrapureblue CIE requirements (0.14, 0.08) defined by the National Television System Committee.
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