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Organic ultralong room temperature phosphorescence (OURTP) materials capable of combining various emission behaviors for diversified optoelectronic properties and applications have recently gained a vigorous development, but it remains a forbidden challenge in designing OURTP molecules with hybrid local and charge-transfer (HLCT) feature, possibly due to the elevated difficulties in simultaneously meeting the stringent requirements of both HLCT and OURTP emitters. Here, through introducing multiple heteroatoms into one-dimensional fused ring of coumarin with moderate charge transfer perturbation in donor-π-acceptor architecture, we demonstrate a HLCT-featured OURTP molecule showing both promoted fluorescence with a quantum yield of 77 % in solution and long-lived OURTP with a lifetime of 251 ms in conventional host material used in electroluminescent device. Thus, efficient OURTP organic light-emitting diodes (OLEDs) were fabricated, exhibiting bright electroluminescence with an exciton utilization efficiency of 85 % and yellow OURTP lasting over 2 s for afterglow. Impressively, the HLCT OURTP-OLEDs can be further optimized to reach an unprecedented total external quantum efficiency (EQE) of ~12 % and OURTP EQE up to 3.11 %, representing the highest performance among the reported OURTP-OLEDs. These impressive results highlight the significance to fuse HLCT and OURTP together in enriching OURTP materials and improving the afterglow OLED performances., (© 2024 Wiley-VCH GmbH.)

The combination of advanced photoluminescence characteristics to photochromism is highly attractive in preparing high-performance multifunctional photo-responsive materials for optoelectronic applications. However, this is rather challenging in material design owing to the limited mechanism understanding and construction principles. Here, an effective strategy to integrate photochromism and afterglow emission in carbon dots (CDs) is proposed through embedding naphthaleneimide (NI) structure in CDs followed by polyvinylpyrrolidone (PVP) encapsulation. The NI-structured CDs-PVP shows intrinsic photochromism owing to the in situ formation of NI-radical anions and controllable multi-stimuli-responsive afterglow behaviors related to the oxygen-trigged triplet exciton quenching and Förster resonance energy transfer (FRET) from the pristine CDs to the photoactivated CDs radicals. Notably, a wide range of appearance colors from colorless to brown, luminescence color transition from blue to yellow, and much elongated afterglow lifetime up to 253 ms are observed. With the extraordinary stimuli-chromic and stimuli-luminescent CDs-PVP film dynamically responsive to multiple external stimuli, reversible secure snapchat, data encryption/decryption and synaptic imaging recognition are realized. These findings demonstrate a fundamental principle to design multi-stimuli-responsive photochromic CDs with afterglow, providing important understandings on the synergic mechanism of dynamic photochromism and emission behaviors and thereby expanding their applications in advanced information anti-counterfeiting and artificial intelligence., (© 2024 Wiley‐VCH GmbH.)

Purely organic afterglow (POA) originating from the slow radiative decay of stabilized triplet excited states has shown amazing potential in many fields. However, achieving highly stable POA with high phosphorescent quantum yield (PhQY) and long lifetime is still a formidable challenge owing to the intrinsically active and sensitive nature of triplet excitons. Here, triplet excitons of phosphors are protected and stabilized by embedding in tricomponent trihapto self-assembled 2D hydrogen-bonded superlattices, which not only enables deep-blue POA with high PhQY (up to 65%), ultralong lifetime (over 1300 ms) and the highest figure-of-merit at room temperature, but also achieves excellent stability capable of resisting quenching effects of oxygen, solvent, pressure, light, and heat. In addition, the POA color is tuned from deep-blue to red via efficient Förster resonance energy transfer from the deep-blue POA emitters to the fluorophores. Moreover, with the high-performance, robust, and full-color POA materials, flexible anti-counterfeit displays and direct-current (DC)-driven lifetime-encrypted color Morse Code applications are facilely realized., (© 2022 Wiley-VCH GmbH.)

Achieving single-component white organic afterglow remains a great challenge owing to the difficulties in simultaneously supporting long-lived emissions from varied excited states of a molecule for complementary afterglow. Here, an extraordinary tri-mode emission from the radiative decays of singlet (S 1 ), triplet (T 1 ), and stabilized triplet (T 1 * ) excited states was proposed to afford white afterglow through modulating the singlet-triplet splitting energy (ΔE ST ) and exciton trapping depth (E TD ). Low-lying T 1 * for yellow afterglow was constructed by H-aggregation engineering with large E TD and trace isomer doping, while high-lying T 1 and S 1 for blue afterglow with thermally activated emission feature were realized by reducing ΔE ST through donor-acceptor molecular design. Therefore, the single-component white afterglow with high efficiency of 14.1 % and a lifetime of 0.61 s was achieved by rationally regulating the afterglow intensity ratios of complementary emissions from S 1 , T 1 , and T 1 *., (© 2021 Wiley-VCH GmbH.)

Organic ultralong room temperature phosphorescence (OURTP) materials with photophysical properties sensitive to external stimulus are highly attractive for advanced applications. However, most OURTP molecules are in crystal and OURTP materials with good practicability and stimulus-responsive character are hard to be achieved. Here, we report, for the first time, the highly efficient, ultralong-lived and deep-blue OURTP materials by simply doping boron phosphor into cyanuric acid host. Host-guest OURTP composites with abundant and tunable H-bond network are highly stable in air with ultralong lifetime of 5.08 s at room temperature. They are sensitive to water, which can strength the H-bond network to significantly enhance OURTP quantum yield from 16.1 % to 37.6 %. Anti-counterfeiting paper was easily prepared for water-jet printing; the jet-printed high-resolution OURTP patterns can be easily erased by solvent fuming for another printing/erasing cycle with high reversibility., (© 2021 Wiley-VCH GmbH.)