We have developed two new carbazole-dendronized emitters based on a green emissive thermally activated delayed fluorescence (TADF) core. Both dendrimers possess excellent thermal stability, good solution processability, and an obvious TADF feature. Non-doped OLEDs based on the emitters formed by a solution process exhibit a maximum external quantum efficiency (EQE) of 13.8%. Remarkably, the EQE remains as high as 13.3% at the high luminance of 1000 cd m-2. To the best of our knowledge, this is one of the highest EQE values for dendrimer-based fluorescent OLEDs, which nearly harvest all of the generated excitons and exhibit a considerably low loss of EQE estimated from 1000 to 5000 cd m-2. Furthermore, we reveal a new emissive approach to utilize the excitons by a combination of both TADF and exciplex emission.