Highly efficient deep-blue light-emitting material based on V-Shaped donor-acceptor triphenylamine-phenanthro[9,10-d]imidazole molecule

Abstract

Based on novel phenanthro[9,10-d]imidazole (PI) chromophore, three deep-blue luminescent donor-acceptor molecules with different molecular configurations at the triphenylamine (TPA) core were designed and synthesized, the linear TPA-1PI, the V-shaped TPA-2PI and the star-shaped TPA-3PI. All three molecules displayed the hybridized local and charge-transfer (HLCT) excited state character, and highly efficient deep blue emissions were observed in their solution state, but only those of linear TPA-1PI and V-shaped TPA-2PI molecule were maintained in the solid state. Meanwhile, the V-shaped TPA-2PI and star-shaped TPA-3PI showed the much better thermal properties. Thus the molecular configurations of HLCT materials significantly influence their solid-state, and the V-shaped TPA-2PI molecule was highlighted because of its both deep-blue emission and good thermal stability. A double-layer device by using TPA-2PI as the emitter showed a highly efficient deep-blue electroluminescence with a very good CIE coordinate of (0.14, 0.08) and high current efficiency of 2.7 cd A−1, which suggest that it might be a promising candidate for emission-layer materials for high-performance deep-blue OLEDs.