AbstractThe operational stability of thermally activated delayed fluorescence (TADF) organic light‐emitting diodes (OLEDs) is an essential property to utilize their efficient triplet harvesting ability and reduce the usage of expensive metal complexes in commercial applications. In this study, a device strategy for extending the device lifetime using the synergistic effects of the hot exciton relaxation and polaron dispersion is demonstrated. By doping a polaron retarder to a conventional TADF‐emitting layer, the lifetime of the blue TADF device is enhanced by 98% at an initial luminance of 1000 cd m−2. Kinetic modeling describing the device degradation indicates that the concurrent contribution via the suppression of exciton and polaron interactions and hot exciton‐related degradation are the origin of the lifetime enhancement. It is demonstrated that the introduction of the polaron retarder finely fits to the ground and that the excited energetic relationship of the host–dopant structure simultaneously improves the operation lifetime and device efficiency without sacrificing other device characteristics.