A benzofuran and acridine merged moiety, 5,5-dimethyl-5,13-dihydrobenzofuro[3,2-c]acridine (BFAc), and a benzothiophene and acridine combined moiety, 5,5-dimethyl-5,13-dihydrobenzothieno[3,2-c]acridine (BTAc), were developed as strong donor moieties of thermally activated delayed fluorescent (TADF) emitters by modifying benzofuran and benzothiophene with an acridine moiety, respectively. Two TADF emitters were synthesized using the BFAc and BTAc donor moieties and a diphenyltriazine acceptor moiety to develop green TADF devices. The two TADF emitters exhibited different emission colors while achieving high external quantum efficiencies of 20.4 and 21.8% in the BFAc and BTAc TADF devices, indicating that BFAc and BTAc worked well as color managing donor moieties of TADF emitters.