Color-Tunable All-Fluorescent White Organic Light-Emitting Diodes with a High External Quantum Efficiency Over 30% and Extended Device Lifetime.

White organic light-emitting diodes (WOLEDs) with high efficiencies and tunable colors attracts considerable interest from the industry and academia. Thermally activated delayed-fluorescence (TADF) emitters can revolutionize such WOLED devices; however, they still suffer from poor performances. In this study, an advanced double-emissive-layer device architecture capable of hole-trapping TADF-sensitized emissions is proposed to not only achieve a recombination zone shift for the tunable colors but also accelerate exciton emission dynamics for high efficiency and alleviated roll-off. The proof-of-concept WOLEDs exhibit significant shifts in their Commission Internationale de l'Eclairage (CIE) coordinates and correlated color temperatures from (0.40, 0.47) and 4088 K at 100 cd m-2 to (0.27, 0.33) and 9269 K at 5000 cd m-2 . Additionally, the maximum external quantum efficiency (EQE) reaches 30.7% and remains >25% over a wide luminance range of 500-5000 cd m-2 , along with an extended LT80 of over 20 000 h at an initial luminance of 100 cd m-2 . This is the first time that all-fluorescent WOLEDs have been used to realize an EQE exceeding 30%, thereby establishing a new benchmark in this field.