The theoretical calculation parameters of TPA-2 were compared with TPA-PZCN, which is a high efficiency red thermally activated delayed fluorescence (TADF) material with an external quantum efficiency close to 30% . As shown in Table , TPA-2 has a narrower bandgap (Egap) than TPA-PZCN (2.08 eV vs. 2.32 eV). The calculated S1 of TPA-2 is also smaller than that of TPA-PZCN, implying that TPA-2 may show a longer emission wavelength than TPA-PZCN in the same solvent. The ΔEST of TPA-2 (0.22 eV) is smaller than that of TPA-PZCN (0.25 eV). The spin-orbit coupling (SOC) was also calculated between S1 and T1 in the geometry of T1. The <S1|Hso|T1> of TPA-2 (0.27 cm -1 ) is larger than that of TPA-PZCN (0.13 cm -1 ), indicating that TPA-2 has a good T1→S1 reverse intersystem crossing (RISC) efficiency.