Achieving Charge-Transfer-Featured Organic Room-Temperature Phosphorescence with Combined High Efficiency and Long Lifetime via V-Shaped D-A Dyads.

The realization of long-lived charge-transfer-based organic room-temperature phosphorescence (3CT-RTP, τPh = 210 ms) via the construction of U-shaped donor-acceptor (D-A) dyads is impeded by suboptimal phosphorescence efficiency ( Φ Ph ${{{\it \Phi}}_{{\mathrm{Ph}}}}$  = 6%). Herein, we reveal that modifying the skeleton of D-A dyads from U-shaped to V-shaped configurations yields 3CT-RTP with both long τPh (150-220 ms) and high Φ Ph ${{{\it \Phi}}_{{\mathrm{Ph}}}}$ (13%-25%). This improvement stems from preserving a substantial degree of forbiddenness in the radiative transition process of the compound while simultaneously increasing its D-A dihedral angle, which can promote more efficient spin-orbit coupling and thus more rapid intersystem crossing. Additionally, augmenting the framework rigidity of a V-shaped D-A dyad can potentially reduce the non-radiative transition rate constant of triplet excitons (knr,T), thereby facilitating the attainment of long τPh and high Φ Ph ${{{\it \Phi}}_{{\mathrm{Ph}}}}$ .