A series of dicyano-imidazole-based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain pure blue-emitting organic lightemitting diodes (OLEDs). The targeted molecules used dicyano-imidazole with a short-conjugated system as the electron acceptor to strong intermolecular π-π interactions, and provide a relatively shallow energy level of the lowest unoccupied molecular orbital (LUMO). The cyano group was selected to improve imidazole as an electron acceptor due to its prominent electron-transporting characteristics. Four different electron donors, that is, 9,9-dimethyl-9,10-dihydroacridine (DMAC), 10H-spiro(acridine-9,9'-fluoren) (SPAC), and 9,9diphenyl-9,10-dihydroacridine (DPAC), were used to alternate the highest occupied molecular orbital (HOMO) energy level to tune the emission color further. The crowded molecular structure in space makes the electron donor and acceptor almost orthogonal, reducing the energy gap (ΔE ST ) between the first excited singlet (S 1 ) and the triplet (T 1 ) states and introducing significant TADF property. The efficiencies of the blue-emissive devices with imM-SPAC and imM-DMAC obtained in this work are the highest among the reported imidazole-based TADF-OLEDs, which are 13.8 % and 13.4 %, respectively. Both of Commission Internationale de l'Eclairage (CIE) coordinates are close to the saturated blue region at (0.17, 0.18) and (0.16, 0.19), respectively. Combining these tailor-made TADF compounds with specific device architectures, electroluminescent (EL) emission from sky-blue to deep-blue could be achieved, proving their great potential in EL applications.

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The fluorescent solution with a resonance displacement of only 12.8 (cm−1) for the CN functional group gives this film a quantum yield as high as 84.8%.

Pure blue‐emitting organic light‐emitting diodes (OLEDs) based on dicyano‐imidazole with thermally activated delayed fluorescence (TADF) have been studied at Providence University (of which a building is shown). The efficiencies obtained in this work are the highest among the reported imidazole‐based TADF‐OLEDs. By combining these tailor‐made TADF compounds with specific device architectures, electroluminescent emission from sky blue to deep blue could be achieved. More information can be found in the Full Paper by C.‐W. Lu et al. (DOI: 10.1002/chem.202101807).