Zhao et al. first reported a BP based TADF compound by combining one to three 9,9dimethylacridan (DMAC) donors to produce a family of red TADF emitters. A distinct TADF character was observed particularly in 3DMAC-BP, an emitter with three DMAC donors, which showed a λPL at 605 nm (in toluene) and 590 nm (in 20 wt% doped films in mCBP). Its rigid, planar framework and the twisted D-A conformation yield a short delayed lifetime τd, of 2.0 µs, resulting in a fast reverse intersystem crossing rate kRISC of 10.01 × 10 5 s -1 and a small ΔEST of 0.05 eV. The high ΦPL of 89% reflects a slow knr of 1.1 × 10 6 s -1 and a fast kr of 9.3 × 10 6 s -1 for this compound. Tang et al. reported a family of related TADF compounds, (1-3) PXZ-BP, using PXZ as the strong donor. The PL progressively red-shifts with an increasing number of PXZ units, with λPL ranging from 578 to 630 nm in (1-3) PXZ-BP. Of these three compounds, 3PXZ-BP, which contains three PXZ units, showed deep red emission with λPL at 680 nm (in toluene) and 630 nm (in 7 wt% doped films in CBP). Despite its relatively fast kRISC of 1.41 × 10 6 s -1 , short τd of 2.0 µs, and small ΔEST of 0.03 eV, 3PXZ-BP was not strongly emissive, with ΦPL of only 22%, which was attributed to a fast knr of 1.05 × 10 7 s -1 . Recently, we reported a related family of TADF compounds (DMACBP, DMACPyBP, DMACBPN, and DMACPyBPN) by combining DMAC donors with BP acceptors and examined the influence of the number of nitrogen atoms within the acceptor moiety on the photophysics of the emitters. DMACPyBP and DMACPyBPN showed the most red-shifted emission in this series, with λPL at 645 nm and 672 nm (in toluene) and 601 nm and 606 nm (in 2 wt% doped films in CBP), respectively. The greater number of nitrogen atoms in DMACPyBP and DMACPyBPN leads to an enhanced CT character of the emissive excited state and faster kRISC of 1.94 × 10 5 and 4.26 × 10 5 s -1 , correlating with their short τd of 5.9 and 2.9 µs and very small ΔEST of 0.01 eV. However, the low ΦPL of 47% and 37% of these two compounds indicated fast non-radiative decay. In a separate study, we modified these structures by replacing DMAC donors with triphenylamines (TPA), which resulted in emissions ranging from orange-red to deep-red for compounds TPAPyAP, TPAPyBP, and TPAPyBPN. Among these, TPAPyBP and TPAPyBPN emit at λPL of 550 and 575 nm (in toluene) and 624 and 675 nm (in 2 and 10 wt% doped films in PPT), respectively. Both compounds are TADF, having small ΔEST values of 0.03 and 0.01 eV and ΦPL of 63 and 57%, but have relatively long τd of 0.61 ms and 0.11 ms, respectively.