Developing red thermally activated delayed fluorescence (TADF) emitters,a ttainable for both high-efficient red organic light-emitting diodes (OLEDs) and non-doped deep red/near-infrared (NIR) OLEDs,ischallenging. Now,two red emitters,B PPZ-PXZ and mDPBPZ-PXZ, with twisted donor-acceptor structures were designed and synthesized to study molecular design strategies of high-efficiency red TADF emitters.B PPZ-PXZ employs the strictest molecular restrictions to suppress energy loss and realizes red emission with aphotoluminescence quantum yield (F PL )of100 AE 0.8 %and external quantum efficiency (EQE) of 25.2 %i nadoped OLED.Its non-doped OLED has an EQE of 2.5 %owingto unavoidable intermolecular p-p interactions.mDPBPZ-PXZ releases two pyridine substituents from its fused acceptor moiety.A lthough mDPBPZ-PXZ realizes al ower EQE of 21.7 %i nt he doped OLED,i ts non-doped device shows asuperior EQE of 5.2 %with adeep red/NIR emission at peak of 680 nm.