Thermally activated delayed fluorescence (TADF) is regarded as the new generation of light-emitting materials in organic light-emitting diode after fluorescent materials and phosphorescent materials. Its high Internal Quantum Efficiency (IQE) and lower cost have attracted a lot of attention, which is a hot field of research of OLEDs for the future. This paper will summarize the achievements of TADF in research. Firstly, the article introduced the background of TADF and demonstrated the mechanism of TADF briefly. Subsequently, the article focused on the progress of TADF in red, green and blue light. Afterwards, the review discussed the limitations and future outlooks of TADF and finally drew a conclusion. These results shed light on guiding future studies focusing on TADF and lay a foundation for subsequent studies.