Chiral sulfur acceptor-based CP-TADF materials with simultaneous TSCT and AIE characteristics

Circularly polarized (CP) luminescence materials have rapidly developed into a prominent research frontier in the field of organic light-emitting diodes (OLEDs) due to their promising applications. However, the development of CP-OLED materials is severely restricted by limited molecular design strategies, currently dominated by the through-bond charge transfer (TBCT) method. Herein, two through-space charge-transfer (TSCT)-typed CP-TADF materials containing point chiral sulfur: (R)-2NSO-CzTPA and (S)–2NSO-CzTPA, were designed and synthesized, using carbazole as a molecular bridge, (R/S)–Br–2NSO as acceptor and triphenylamine (TPA) as donor. The results suggested that the distance between donor and acceptor planes was 3.231∼3.695 Å and there were substantial interactions between them, which signified the existence of the suitable TSCT pathway in 2NSO-CzTPA. 2NSO-CzTPA manifested a small ΔE_ST of 0.11 eV and a short delayed fluorescence lifetime (τ_d) of only 1.15 μs, indicating good TADF feature. 2NSO-CzTPA exhibited sky-blue emission at 489 nm with strong AIE property and PLQY of 89.0%. Notably, (R/S)–2NSO-CzTPA displayed enhanced CPL characteristic with an asymmetric factor |g_lum| of 1.2 × 10⁻³. The solution-processed OLED based on 2NSO-CzTPA emitted pure blue electroluminescence at 465 nm. The EQE_max, CE_max, and PE_max were 0.2%, 0.4 cd A⁻¹, and 0.3 lm·W⁻¹ for the device, respectively.