These results further verify the dual-RTP property of p-ClTPA in crystals, because the shortwavelength peak can be assigned to the radiative transition from the upper-lying T2 state populated from the T1 state under thermal activation. In contrast, with the temperature gradually increasing from 77 K to room temperature, the phosphorescence emission peak at ~ 515 nm is gradually weakened and eventually replaced by the delayed fluorescence peak at ~ 460 nm and gradually intensified. This result reveals that the delayed fluorescence of o-ClTPA can be attributable to the TADF which is occurred via efficient RISC under thermal activation.