The development of organic semiconductors exhibiting strong CPL, 2PA, high photoluminescence quantum yield, and long-lived delayed fluorescence would be of significant value as deep tissue penetrating bioimaging agents showing high resolution. Although examples of organic CP-TADF emitters and 2PA-TADF emitters have each been documented and exploited in CP-OLEDs and in biological imaging, respectively, the design of 2PE-CPL-TADF organic compounds remains unprecedented, due to their low PL dissymmetry factor (gPL) and small 2PA σ2. In this work, we designed and synthesized two systems, DDCzBPh and DDCzBPy, consisting of two annulated MR-TADF units to a central naphthyl or quinazinyl group, respectively, which exhibit large |gPL| and σ2 values, high PL, and long-lived delayed fluorescence. We demonstrate for the first time two-photon CPL of TADF emitters, with their circularly polarized brightness above 0.1 GM, demonstrating their potential for biological imaging.
Wu et al. (Wed,) studied this question.
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