Three thermally activated delayed fluorescence (TADF) molecules, namely PQ1, PQ2, and PQ3, are composed of electron‐accepting (A) tetrabenzoa,cphenazine (TBPZ) and electron‐donating (D) phenoxazine (PXZ) units are designed and characterized. The combined effects of planar acceptor manipulation and high steric hindrance between D and A units endow high molecular rigidity that suppresses nonradiative decay of the excitons with improved photoluminescence quantum yields (PLQYs). Particularly, the well‐aligned excited states involving a singlet and a triplet charge‐transfer excited states and a localized excited triplet state in PQ3 enhances the reverse intersystem crossing rate constant (kRISC) with a short delay lifetime (τd). The orange–red OLED based on PQ3 displays a maximum external EL quantum efficiency (EQE) of 27.4 % with a well‐suppressed EL efficiency roll‐off owing to a completely horizontal orientation of the transition dipole moment in the film state. The expansion of TBPZ acceptor plane well‐controlled the excited states involving 1CT, 3CT and 3LE states, which enhances the kRISC by remarkably shortening τd and induced a completely horizontal orientation of the TDM. Consequently, PQ3 displayed an orange red EL max at 586 nm, PLQY of ca. 83 %, kRISC of 8×105 s−1, τd of 2.7 μs, S values of −0.49, and deliver high EQE of 27.4 %.