Cross-shaped anthracene-based emitter with low T₁ energy for high-performance BT.2020 green hot-exciton-sensitized...

Efficient utilization of triplet excitons is crucial for achieving high efficiency and high stability in organic light-emitting diodes (OLEDs). Among common fused aromatic hydrocarbons, anthracene possesses the lowest triplet (T₁) energy, which is presumably the key reason for its commercial application. A low T₁ not only enhances the bond dissociation energy threshold of emitters during device operation and prolongs device lifetime, but it may also promote the hot exciton characteristics, breaking the bottleneck of exciton utilization efficiency (EUE) limited by the triplet-triplet annihilation mechanism. Herein, we found that the T₁ energy of anthracene-based material 2PAn2C with tetra-substitution at the 2,6,9,10-positions is 0.12 eV lower than that of conventional 9,10-substituted anthracene derivatives (T₁ = 1.8 eV), representing the lowest value among reported anthracene-based materials. Photophysical investigations reveal that the reduced T₁ originates from the electron cloud delocalization induced by the symmetry breaking of the tetra-substituted framework. This structural feature facilitates efficient triplet harvesting through the hot exciton channel, enabling an EUE of 71% in non-doped devices. Moreover, 2PAn2C serves as an effective host for hot-exciton-sensitized green OLEDs, yielding CIE coordinates of (0.297, 0.667), a small full width at half maximum of 35 nm, and a high external quantum efficiency of 13.32%.