Emission and Absorption Tuning in TADF B,N?Doped Heptacenes: Toward Ideal?Blue Hyperfluorescent OLEDs

Developing high-efficiency purely organic blue light-emitting diodes (OLEDs) that meet the stringent industry standards is a major current research challenge. Hyperfluorescent device approaches achieve in large measure desired high performance by combining advantages of thermally activated delayed fluorescence (TADF) assistant dopant with narrowband deep-blue multi-resonant TADF (MR-TADF) terminal emitter. However, this approach requires suitable spectral overlap to support Förster resonance energy transfer (FRET) between two. Here, color tuning recently reported MR-TADF B,N-heptacene core through control boron substituents demonstrated. While there little impact on intrinsic properties—as both singlet and triplet energies decrease tandem—this improves emission coordinate as well for hyperfluorescence OLEDs (HF OLEDs). Crucially, red-shifted more intense absorption allows new emitter pair high-performance maximum external quantum efficiency (EQEmax) 15% at coordinates (0.15 0.10). The values recorded practical luminance 100 cd m–2 are among highest HF CIEy ? 0.1.