3ACR-TRZ, an analogue of DMAC-TRZ containing 3 donor groups, reported by Wada et al. shows somewhat similar photophysical properties to DMAC-TRZ, with near unity FPL (98%; in 16 wt% CBP) and a slightly red-shifted emission (λPL: 504 nm; in 16 wt% CBP). The small red-shift implies that there is only a weak influence on the stabilization of the singlet state by increasing the number of DMAC units. However, the multiple donors could further delocalize the distribution of HOMO, thus leading to a smaller ΔEST (0.015 eV). The solutionprocessed device showed an EQEmax of 18.6% at a emission of λEL~520 nm. Analogue compounds containing either trisubstituted PXZ or PTZ donor groups have also been reported. Similar evolution of the photophysical properties from the linear D-A compounds to the D3-symmetric analogs was observed for tri-PXZ-TRZ (λPL: 568 nm; FPL: 58% in 6 wt% mCP; τd: 1.10 µs in toluene) and TRZ3(Ph-PTZ) (λPL: 575 nm in toluene; τd: 7.2 µs in 2 wt% mCP). The OLEDs based on TRZ3(Ph-PTZ) shows yellowish-green electroluminescence with a λEL ~550 nm and exhibits a much higher EQEmax of 17.4% than those of the devices of i-DMAc-TRZ (λPL: 452 nm; FPL: 55%; τd: 1840 µs; ΔEST: 0.35 eV; in 3 wt% DPEPO) is a constitutional isomer of DMAC-TRZ but where the phenylene bridge is C-bound para to the nitrogen atom of the DMAC donor (Figure ). Distinct from the highly twisted When compared to i-DMAC-TRZ, DTPSAF has a similar lPL but has a higher FPL due to the restricted rotational flexibility conferred by the rigid bulky SpiroAC group. Addition of methyl groups on the phenylene bridge of DTPSAF to generate DTTSAF further enhances the restriction of the rotation and produces a more twisted conformation, leading to a near unity FPL and a 9 nm blue-shift in the emission for DTTSAF (λPL: 450 nm; FPL: 100%; in 10 wt% mCP), and DTXSAF (λPL: 446 nm; FPL: 98%; in 10 wt% mCP), which contain tolueneyl and xylenyl bridges, respectively. Distinct to i-DMAC-TRZ, there is no reported TADF in these analogues, which based on DFT calculations can be ascribed to their too large DEST values. The EQEs of the DTTSAF-and DTXSAF-doped OLEDs (6.2 and 7.7%, respectively) were higher than that of the DTPSAF-doped device (5.7%) due to the higher FPL values of DTTSAF (FPL: 100%) and DTXSAF (FPL: 98%) over that of DTPSAF (FPL: 82%). DTXSAF-based OLEDs show the deepest blue emission with CIE coordinates of (0.15, 0.08) and λEL of 444 nm compared to those of DTPSAF (λEL of 460 nm) and DTTSAF (λEL of 448 nm). Wu et al. reported two compounds DPAC-TRZ (λPL: 478 nm; FPL: 82%; ΔEST: 0.133 eV; in 12 wt% mCPCN) and SpiroAC-TRZ (λPL: 480 nm; (FPL: 100%; ΔEST: 0.072 eV; in 12 wt% mCPCN), both of which are derivatives of DMAC-TRZ but where the two methyl groups on the acridan are replaced by phenyl and 2,2′-biphenyl (spirobiphenyl), respectively. In contrast to DMAC-TRZ, the structural modifications of the donor contribute to a blue-shift of the emission. The fluorescence (phosphorescence) spectra of SpiroAC-TRZ, DPAC-TRZ, and DMAC-TRZ in in 12 wt% mCPCN films are structureless with lPL of 480 nm (483 nm), 478 nm (482 nm), and 495 nm (504 nm), respectively. Both compounds possess small ΔEST values though larger than that of DMAC-TRZ, thus leading to relatively short delayed lifetime (DPAC-TRZ: τd of 2.9 µs; SpiroAC-TRZ: τd of 2.1 µs). DPAC-TRZ has a lower FPL of 82%