Adv. Mater. 2016, 28, 5975–5979

Jing Zhang, Chunbo Duan, Chunmiao Han, He Yang, Ying Wei, and Hui Xu * Balanced Dual Emissions from Tridentate Phosphine-Coordinate Copper(I) Complexes toward Highly Efficient Yellow OLEDs. (Adv. Mater. 2016, 28, 5975–5979.)

Here, we used a tridentate phosphine ligand 2,2′-(phenylphosphinediyl)bis(2,1-phenylene) bis(diphenylphosphine) (TTPP) to construct three tetracoordinate mononuclear Cu(I) complexes TTPPCuX (X = Cl, Br, I) with extremely stable tetrahedral geometry as shown by their single-crystal structures. The S₁ and T₁ configurations of TTPPCuBr as a representative are basically unchanged in comparison to the ground state (S₀), owing to its rigid coordination geometry. Through optimizing excited-state and transition characteristics, the balanced dual emissions with PH proportion as high as ≈40% are successfully realized by TTPPCuI, endowing its yellow devices with the state-of-the-art EQE of 16.3% and the negligible EQE roll-off as low as 6% at 1000 cd m ⁻², which is one of the best results to date among Cu(I) complex-based OLEDs. This work not only convincingly manifests the superiority of dual emissive materials in exciton harvesting, but also demonstrates a feasible strategy for emission proportion modulation, paving the way for further development and applications of this kind of materials.