Ultralong organic phosphorescence (UOP) has attracted increasing attention due to its potential applications in optoelectronics, bioelectronics, and security protection. However, achieving UOP with high quantum efficiency (QE) over 20 % is still full of challenges due to intersystem crossing (ISC) and fast non‐radiative transitions in organic molecules. Here, we present a novel strategy to enhance the QE of UOP materials by modulating intramolecular halogen bonding via structural isomerism. The QE of CzS2Br reaches up to 52.10 %, which is the highest afterglow efficiency reported so far. The crucial reason for the extraordinary QE is intramolecular halogen bonding, which can not only effectively enhance ISC by promoting spin–orbit coupling, but also greatly confine motions of excited molecules to restrict non‐radiative pathways. This work provides a reasonable strategy to develop highly efficient UOP materials for practical applications.
Flexible hydrogen-bonded organic frameworks (FHOFs) are quite rare but promising for applications in separation, sensing and host-guest chemistry. They are difficult to stabilize, making their constructions a major challenge. Here, a flexible HOF (named 8PN) with permanent porosity has been successfully constructed. Nine single crystals of 8PN with different pore structures are obtained, achieving a large-scale void regulation from 4.4% to 33.2% of total cell volume. In response to external stimuli, multimode reversible structural transformations of 8PN accompanied by changes in luminescence properties have been realized. Furthermore, a series of high-quality co-crystals containing guests of varying shapes, sizes, aggregation states and even amounts are obtained, showing that 8PN can adapt to different guests by regulating the molecular conformations and assembling forms of its building blocks. The unexpected flexibility of 8PN makes it a promising material for enriching the applications of existing porous materials.
Soft luminescent materials are attractive for optoelectronic applications, however, switching dominant chromophores for property enrichment remains a challenge. Herein, we report the first case of a soft organic molecule (DOS) featuring selective expression of chromophores. In response to various external stimuli, different chromophores of DOS can take turns working through conformation changes, exhibiting full‐colour emissions peaking from 469 nm to 583 nm from ten individual single crystals. Dynamic triplet‐exciton behaviours including thermally activated delayed fluorescence (TADF), room‐temperature phosphorescence (RTP), mechanoluminescence (ML), and distinct mechano‐responsive luminescence (MRL) can all be realized. This novel designed DOS molecule provides a multifunctional platform for detection of volatile organic compounds (VOCs), multicolour dynamic displays, sensing, anticounterfeiting, and hopefully many others.
Mechanoluminescence (ML) materials are environmentally friendly and emit light by utilizing mechanical energy. This has been utilized in light sources, displays, bioimaging, and advanced sensors. Organic ML materials are strongly limited to application by in situ unrepeatable ML. Now, in situ solar-renewable organic ML materials can be formed by introducing a soft alkyl chain into an ML unit. For the first time, the ML from these polycrystalline thin films can be iteratively produced by simply recrystallizing the fractured crystal in situ after a contactless exposure to sunlight within a short time (≤60 s). Additionally, their ML color and lifetime can be also easily tuned by doping with organic luminescent dyes. Therefore, large-area sandwich-type organic ML devices can be fabricated, which can be repeatedly used in a colorful piezo-display, visual handwriting monitor, and sensitive optical sensor, showing a lowest pressure threshold for ML of about 5 kPa.
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