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

Abstract 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.