The solution-state PL spectra (Figure ) exhibit structureless deep red (DR) to near-infrared (NIR) emission, with λPL at 643, 743, and 722 nm for DMACPyBP, PXZPyBP, and DPACzPyBP, respectively, and corresponding Stokes shifts of 174 nm, 223 nm and 212 nm. This pattern reflects stabilization of the S1 state with increasing donor strength, in line with the TDA-DFT calculations. The high energy emission band for PXZPyBP, and DPACzPyBP is likely from the LE emission of the donor. The absolute ΦPL values in degassed toluene solution are 23.3% for DMACPyBP, 8.2% for PXZPyBP, and 10.4% for DPACzPyBP, which decrease to 11.1, 4.6, and 6.5%, respectively, in the presence of oxygen. The PL decays of the three emitters in toluene under degassed and aerated conditions were measured using timecorrelated single-photon counting (TCSPC). Average prompt lifetimes (τp,avg) of 28.2 ns for DMACPyBP, 17.2 ns for PXZPyBP, and 23.7 ns for DPACzPyBP were recorded in degassed toluene. DMACPyBP also shows a delayed lifetime, with τd,avg of 4.3 µs (measured using multichannel scanning, (MCS)), suggesting an efficient RISC due to its smaller DEST, while PXZPyBP and DPACzPyBP did not show any delayed emission, which is likely due to competitive nonradiative decay in solution, a behavior often observed in NIR-TADF compounds. Exposure to air significantly reduces the PL emission intensity of DMACPyBP by a factor of 3.5, and the delayed lifetime by 7.7-fold (Figures S12). a RT value was obtained under an oxygen-free atmosphere with λexc= 375. b Time-resolved PL decays were recorded at 298 K under an oxygen-free atmosphere (λexc= 375 nm). The average lifetime ( 𝜏 !"# = 𝜏 $ 𝜔 $ + 𝜏 % 𝜔 % ), where 𝜔 $ = 𝐴 $ 𝜏 $ 𝐴 $ 𝜏 $ + 𝐴 % 𝜏 % ⁄ , was calculated. TCSPC and MCS modes were used to record prompt and delayed decays, respectively. c ∆EST values were obtained from the onset of the prompt fluorescence (1-100 ns) and phosphorescence spectra (1-10 ms) at 77 K, with λexc= 375 nm. d ΦPL of 1 wt% doped thin films was measured using an integrating sphere at 298 K (λexc = 375 nm) under an oxygen-free atmosphere. Values quoted inside parentheses represent measurements in air. Thin films of PMMA, CBP, and PPT were prepared by spin-coating.