Organic materials that exhibit thermally activated delayed fluorescence (TADF) are an attractive class of functional materials that have witnessed a booming development in recent years. Since Adachi et al. reported high-performance TADF-OLED devices in 2012, there have been many reports regarding the design and synthesis of new TADF luminogens, which have various molecular structures and are used for different applications. In this review, we summarize and discuss the latest progress concerning this rapidly developing research field, in which the majority of the reported TADF systems are discussed, along with their derived structure-property relationships, TADF mechanisms and applications. We hope that such a review provides a clear outlook of these novel functional materials for a broad range of scientists within different disciplinary areas and attracts more researchers to devote themselves to this interesting research field.

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.

The interfacial properties for the buried junctions of the perovskite solar cells (PSCs) play a crucial role for the further enhancement of the power conversion efficiency (PCE) and stability of devices. Delicate manipulation of the interface properties such as the defect density, energy alignment, perovskite film quality, etc., guarantees efficient extraction and transport of photogenerated carriers. Herein, chlorobenzenesulfonic potassium salts are presented as a novel multifunctional agent to modify the buried tin oxide (SnO2)/perovskite interface for regular PSCs. The increasing number of carbon‐chlorine bonds (CCl) in 2,4,5‐trichlorobenzenesulfonic potassium (3Cl‐BSAK) exhibit efficient interaction with uncoordinated Sn, effectively filling oxygen vacancies in the SnO2 surface. Importantly, synergistic effects of the functional group‐rich organic anions and the potassium ion are achieved for reduced defect density, carrier recombination, and hysteresis. A champion PCE of 24.27% and the open‐circuit voltage (VOC) up to 1.191 V for modified devices are obtained. The unencapsulated devices maintain 80% of their initial PCE after aging at 80 °C for 800 h in the atmosphere and 95% after aging for 100 d. With 3Cl‐BSAK decoration, a high efficiency semitransparent PSC with a PCE of 12.83% and an average visible light transmittance (AVT) over 27% is also obtained.

A panoramic review of the latest progress regarding mechano-responsive luminescence of tetraphenylethylene derivatives with aggregation-induced emission properties.

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.