The crux of the challenge lies in addressing the efficacy of current hybrid WOLEDs for lighting applications. It is impossible to review all of the work in the business community, but it is clear that the progress on the device efficiency has been rather limited since 2006, especially when compared with that of all-phosphorescent WOLEDs. And so the primary goal should remain on the improvement of the conversion from electricity to useful light in hybrid WOLEDs. The complete utilization and rational management of the electrically generated singlet and triplet excitons is the basic concept toward obtaining high internal efficiency, which is strongly dependent on the materials-combination and device engineering.