Within the past two decades, chromophores, which show aggregation‐induced emission (AIE), have gained considerable attention with respect to the development of luminescent liquid crystals. In contrast to common luminogens, AIE emitters do not suffer from aggregation‐caused quenching of the emission in the solid state. In this review, we summarize the recent development in the field of AIE‐active liquid crystals and show first model devices, which already prove the application potential of these materials. Currently, three different approaches are followed, to get access to luminescent liquid crystals––namely the synthetic approach yielding luminescent mesogens, the doping approach, and the supramolecular approach, which will be described and discussed in detail in this review.
We mapped the entire visible range of the electromagnetic spectrum and achieved white light emission (CIE: 0.31, 0.34) by combining the intrinsic ns‐fluorescence with ultralong ms‐phosphorescence from purely organic dual emitters. We realized small molecular materials showing high photoluminescence quantum yields (ΦL) in the solid state at room temperature, achieved by active exploration of the regioisomeric substitution space. Chromophore stacking‐supported stabilization of triplet excitons with assistance from enhanced intersystem crossing channels in the crystalline state played the primary role for the ultra‐long phosphorescence. This strategy covers the entire visible spectrum, based on organic phosphorescent emitters with versatile regioisomeric substitution patterns, and provides a single molecular source of white light with long lifetime (up to 163.5 ms) for the phosphorescent component, and high overall photoluminescence quantum yields (up toΦL=20 %).
14 November 2022 in Chemistry – A European Journal
For a long time, luminescence phenomena were strictly distinguished between the emission of isolated molecules in dilute solutions or close‐packed structures such as in powders or aggregates. This changed with the breakthrough observation of dual‐state efficient materials, which led to a rapid boost of publications examining the influence of structural features to achieve balanced emission with disregarded molecular surroundings. Some first general structural design concepts have already been proposed based on reoccurring patterns and pivotal motifs. However, we have found another way to classify these solution and solid‐state emitters (SSSEs). Hence, this minireview aims to present an overview of published structural features of SSSEs while shining light on design concepts from a more generalized perspective. Since SSSEs are believed to bridge the gap of hitherto known aggregation‐sensitive compound classes, we hope to give future scientists a versatile tool in hand to efficiently design novel luminescent materials.