Over 30 000 h Device Lifetime in Deep Blue Organic Light‐Emitting Diodes with y Color Coordinate of 0.086 and Current Efficiency of 37.0 cd A−1

Abstract The development of highly efficient and long‐life deep blue devices has been an ongoing challenge in the field of organic light‐emitting diodes (OLEDs) because of the short lifetime inherent to highly efficient blue devices. The efficiency and lifetime issues of the deep blue OLEDs are resolved in this work by engineering the device architecture by managing the triplet excitons of the phosphorescence and thermally activated delayed fluorescence (TADF) emitters. The CN‐modified imidazole type Ir emitter and boron‐based TADF emitter with similar emission energy are combined to develop an energy exchanging phosphorescence and TADF (EPHTADF) device. An emission mechanism inducing both forward and backward energy transfer concurrently between the Ir phosphor and TADF emitter shortens the triplet exciton lifetime of the two emitters, which dramatically enhances the device lifetime of the blue devices. Deep blue OLEDs triggering EPHTADF emission ultimately yields device performances including high current efficiency (CE) of 37.0 cd A −1 , color‐coordinate corrected CE of 430.9 cd A −1 , extrapolated device lifetime of more than 30 000 h, and deep blue color coordinates of (0.122, 0.086). This work demonstrates the potential of EPHTADF devices to serve as the solution to the problematic issues of the blue OLEDs.