Currently, HF OLEDs that utilize D-A type TADF materials as sensitizers for multi-resonance TADF (MR-TADF) dopants with narrow FWHM emissions are considered as a promising technique to fulfill the requirements for ultra-high-definition display because they can achieve high EL efficiency and high color purity simultaneously. Based on Förster energy transfer from sensitizer to dopant, HF OLEDs can make full use of the advantages of high exciton utilization of the sensitizers and the narrow emissions of the dopants.