Multi-resonance induced by boron and nitrogen atoms in opposite resonance positions endows a thermally activated delayed fluorescence (MR-TADF) emitter with a strikingly small full width at half maximum of only 26 nm and excellent photoluminescence quantum yield of up to 97.48 %. The introduction of a carbazole unit in the para position of the B-substituted phenyl-ring can significantly boost up the resonance effect without compromising the color fidelity, subsequently enhancing the performances of the corresponding pure blue TADF-OLED, with an outstanding external quantum efficiency (EQE) up to 32.1 % and low efficiency roll-off, making it one of the best TADF-OLEDs in the blue region to date. Furthermore, utilizing this material as host for a yellow phosphorescent emitter, the device also shows a significantly reduced turn-on voltage of 3.2 V and an EQE of 22.2 %.

Materials with circularly polarized luminescence (CPL) activity have immense potential applications in molecular switches, optical sensors, information storage, asymmetric photosynthesis, 3D optical displays, biological probe, and spintronic devices. However, the achiral architectures of most of the luminophores severely limit their practical needs. Within this context, molecular ferroelectrics with striking chemical variability and structure–property flexibility bring light to the assembly of CPL-active ferroelectric materials. Herein, we report organic–inorganic perovskite enantiomorphic ferroelectrics, (R)- and (S)-3-(fluoro­pyrrol­idinium)­MnBr3, undergoing a 222F2-type ferroelectric phase transition at 273 K. Their mirror relationships are verified by both single-crystal X-ray diffraction and vibrational circular dichroism (VCD). Furthermore, the corresponding Cotton effect for two chiral crystals was captured by mirror CPL activity. This may be assigned to the inducing interaction between the achiral luminescent perovskite framework and chiral organic components. As far as we know, this is the first molecular ferroelectric with CPL activity. Accordingly, this will inspire intriguing research in molecular ferroelectrics with CPL activity and holds great potential for the development of new optoelectronic devices.

The research in circularly polarized luminescence has attracted wide interest in recent years. Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors, and on the other side, are focused on the exploitations of these materials in optoelectronic applications. This review summarizes the recent frontiers (mostly within five years) in the research in circularly polarized luminescence, including the development of chiral emissive materials based on organic small molecules, compounds with aggregation-induced emissions, supramolecular assemblies, liquid crystals and liquids, polymers, metal-ligand coordination complexes and assemblies, metal clusters, inorganic nanomaterials, and photon upconversion systems. In addition, recent applications of related materials in organic light-emitting devices, circularly polarized light detectors, and organic lasers and displays are also discussed.

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