<p></p><p>Control of nonradiative deactivation of triplet states
and tuning the singlet-triplet energy gap (ΔE<sub>ST</sub>) are the major
challenges to develop materials exhibiting thermally activated delayed
fluorescence (TADF) and room temperature phosphorescence (RTP). Herein, we
propose a new class of multichromophoric tridonor-acceptor (D<sub>3</sub>-A)
compounds with rigid and flexible π-spacer
having N-rich pyridoquinoxaline (PQ) and pyridopyrazine (PZ) acceptor core,
respectively. The molecule with carbazole (Cz) donors at <i>meta</i> to
quinoxaline (QX) nitrogen of rigid PQ core exhibits TADF. Whereas, the
variation of the linkage position of Cz to PQ as well as twisted and flexible PZ
core show predominantly RTP due to relatively higher singlet-triplet energy gap
(ΔE<sub>ST</sub>). Increasing the donor strength with phenoxazine (PO) in PZ
system leads to simultaneous TADF and RTP. Further, we demonstrate the
promising scope of all-organic triplet harvesting
materials in solid-state security encryption.</p><br><p></p>