Balanced Dual Emissions from Tridentate Phosphine‐Coordinate Copper(I) Complexes toward Highly Efficient Yellow OLEDs

Dual emissive copper(I) halide complexes TTPPCuX (X = Cl, Br, I) with a triphosphine ligand and stable tetrahedral geometries are constructed, in which TTPPCuI successfully achieves the balanced dual thermally activated delayed fluorescence and phosphorescence (PH) emissions with PH fraction of 39% at ambient temperature, supporting the equal triplet exciton reallocation for the state-of-the-art device performance.