Achieving Balanced Electrical Performance of Host Material through Dual N–P═O Resonance Linkage for Efficient Electroluminescence

Abstract

Developing high-performance host materials is one of the biggest challenges for blue and white thermally activated delayed-fluorescence (TADF) organic light-emitting diode (OLED) technology due to the rigorous requirements of both efficient carrier flux ability and high triplet energy (E T) levels in static donor–acceptor molecules. Here, with the aid of a dual-resonance strategy, a host molecule showing dynamic adaption features in the acceptor–resonance–donor–resonance–acceptor (A–r–D–r–A) molecular configuration has been successfully developed through the implantation of two acceptors of diphenylphosphine oxide into electron-donating 5,10-dihydrophenazine with N–PO resonance linkages. Owing to the dual enantiotropic N+P–O– resonances, the designed A–r–D–r–A molecule exhibits an extraordinarily balanced charge flux transportation attribute at high E T (2.96 eV). Excitingly, blue and warm-white TADF OLEDs hosted by the A–r–D–r–A molecule exhibit outstanding external quantum efficiencies of 14.7 and 20.3%, respectively. Our studies not only broaden the scope of resonance molecules but also indicate that a resonance structure is an effective linkage to develop optoelectronic materials with dynamically adaptive properties.

Resonance-Induced Dynamic Triplet Exciton Population for Photoactivated Organic Ultralong Room Temperature Phosphorescence

“…44 The C�O bond 45 These results demonstrate the presence of dynamically variable tautomerization in the resonance structural units of HPN and FPN. The bond orders of N−C in N−C�O of HPN and FPN are 1.18 and 1.17, respectively, based on their single crystal structures (Table S2), which are larger than the standard C−N bond order (∼1), 46 indicating that the C−N bond possesses partial double bond characteristics. The E RV values of tautomerization between N−C�O and N + �C−O − of HPN and FPN were calculated based on eq 1: 31…”

Carbazole and dibenzo[b,d]furan-based hole transport materials with high thermal stability

“…Organic light emitting diodes (OLEDs) have received extensive attention and experienced rapid development, and will dominate the display field in the few next decade is [1][2][3][4] due to their high electroluminescent (EL) efficiency, full color, fast response, wide view angle, and good plasticity. [5][6][7][8][9][10][11] To date, the organic layer structure of the device has been continuously optimized from single to multi-layer, 12,13 where among them, hole transport materials 14 (HTMs) require the greatest materials consumption.…”