than the fluorescence and TADF emitters to prevent reverse energy transfer. Moreover, it is also very important to prevent Dexter energy transfer (DET) among triplet states to avoid loss of triplet exciton, which is achieved through efficient kRISC, and the use of less doping concentrations of emitters. Finally, a key requirement is to control carrier trapping, which is essential to forbid the formation of triplet exciton in the dopant fluorescence emitter. The implementation of bulkier groups in fluorescence emitter is the most suitable approach to control it. In the last few years, resonance (MR)-TADF terminal emitters have been greatly used in HF-OLEDs. Concerning the current use of MR-TADF terminal emitters, they should have short-range charge transfer characteristics, a small Stoke shift and efficient kRISc. The FRET processes are evaluated by using simple following mathematical equations: