Through-bond charge transfer(CT)could easily occur be-tween an electron donor(D)and an electron acceptor(A),which is fundamental to design various D-A type emissive materials for organic light-emitting diode(OLED)applica-tion.Although D-A type emitters have been developed for many years,what makes them in the spotlight is the rise of thermally activated delayed fluorescence(TADF)materials.In 2012,Adachi et al.[1]reported a series of D-A emitters with TADF features to fully utilize electrogenerated ex-citons.After the pioneer work,numerous TADF materials with D-A structure were extensively explored for the appli-cation of organic light emitting diodes(OLEDs)[2].