In summary, all-fluorescence two-color WOLEDs with a sandwich configuration consisting of an orange EML of delayed fluorescence 4CzTPNBu doped in delayed fluorescence TCP-BP-SFAC host located between two sky-blue EMLs of TCP-BP-SFAC neat films is proposed. Owing to the outstanding EL efficiency, small carrier injection barrier and balanced ambipolar carrier transport of TCP-BP-SFAC in neat film, the turn-on voltages of the devices are successfully lowered, and ultrahigh PEs and EQEs of up to 130.7 lm W -1 and 31.1% are achieved. The sandwich configuration effectively alleviates exciton quenching caused by the electron-trapping effect of 4CzTPNBu. Based on the best performed two-color device configurations, a red EML of red fluorescence DBP doped in TCP-BP-SFAC host is introduced to improve the color quality, which is sensitized by the adjacent orange EML via an out-of-phase sensitization configuration. In such device configuration, the electron-trapping effect of 4CzTPNBu can exert positive effect of preventing excitons from recombining at DBP dopant, and the FET from 4CzTPNBu greatly enhances the red emission efficiency of DBP. The generated all-fluorescence three-color WOLEDs attain remarkable PEs and EQEs of up to 106.8 lm W -1 and 30.8%. More importantly, both two-color and three-color WOLEDs not only acquire record-beating PEs but also enjoy superb efficiency stability, with much smaller PE roll-offs at operational luminance than those of the state-of-the-art WOLEDs. Finally, on the basis of most efficient two-color and three-color device configurations, further device optimization furnishes outstanding comprehensive performances of low driving voltages, large luminance, high EL efficiencies and long operational lifetimes for WOLEDs. The mechanism investigation demonstrates that, in addition to the suitable HOMO and LUMO energy levels, the host-tuning effect and electron-trapping effect matter significantly for realizing these high-performance WOLEDs. The design strategy for constructing highly efficient sensitization system presented in this work holds great practical potentials for the advancement of energy-conserving WOLEDs.