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Realizing highly efficient organic light‐emitting diodes (OLEDs) based on "hot exciton" emitters is crucial for the widespread use of purely organic electroluminescence. Herein, it is demonstrated that the radiative decay rate, modulated by molecular configuration, plays a vital role in determining the optoelectronic properties of hot exciton materials. The proof‐of‐concept isomers, TPA‐1IPCN and TPA‐3IPCN, and TPA‐1IANCN and TPA‐3IANCN are intentionally designed and successfully synthesized. By employing a novel donor–acceptor–acceptor (D–A'–A) molecular architecture, implementing a molecular isomerization strategy, incorporating diverse steric hindrance moieties, and strategically manipulating the positioning of functional groups, precise modulation of the molecular configuration can be achieved to enable accurate regulation of the radiative decay rate. Consequently, various optoelectronic properties, including photoluminescent wavelength, photoluminescence quantum yield, fluorescence lifetime, packing mode in aggregated state, and molecular horizontal dipole ratios in films, undergo significant modifications. As a result, non‐doped blue OLED based on TPA‐1IPCN exhibits outstanding maximum external quantum efficiency (EQE) of 10.3% with minimal efficiency roll‐off—one of the highest reported values for blue OLEDs based on hot exciton materials. [ABSTRACT FROM AUTHOR]

The 5d→4f transition of Ce3+ is allowed by the electric dipole and the parity selection rule and the position/intensity of the 5d excited state is strongly dependent on the materials' composition and atomic structure. Herein, the composition‐dependent luminescence properties of Ce3+ in CsPbCl3‐xBrx (0 ≤ x ≤ 3) perovskite nanocrystals (PeNCs) are systematically revealed. It's observed that the 5d‐4f broadband emission of Ce3+ is greatly improved by optimizing the Cl:Br ratio due to the efficient energy transfer from excitons to Ce3+. Folic acid, a vitamin which is an extremely important cofactor, is introduced to regulate the film formation by interacting with uncoordinated ions. The modified CsPbCl1.5Br1.5 PeNCs with photoluminescence quantum yield of 91% represent a novel and extremely efficient white nanophosphor. Then, white light‐emitting diodes (WLEDs) are constructed by combining Ce3+‐doped PeNCs with 400‐nm ultraviolet chips with a luminous efficiency of 120.3 lm W−1, which is the most efficient perovskite single‐component WLED. Moreover, the blue‐violet LEDs are fabricated with external quantum efficiency of 0.84%, representing extremely high level of 400–435 nm perovskite LEDs. This work demonstrates the strategy in realizing high‐efficiency wavelength‐tunable PeNCs, motivating the further exploration of Ce3+‐doped perovskites in optoelectronic devices. [ABSTRACT FROM AUTHOR]

High‐performance light‐emitting/detecting bifunctional optoelectronic devices based on halide perovskites are hindered by the less efficient carrier transport and radiative recombination processes. The density of defects (i.e., surface and bulk defects) is the main factor affecting carrier transport, radiation recombination, and determining performance in perovskites. Therefore, techniques to effectively regulate defects are highly needed. Here, a convenient and effective strategy, electrical doping, is proposed to flexibly regulate defect density, resulting in dramatically enhanced light‐emitting (i.e., fluorescence and carrier lifetime) and light‐detecting performance (i.e., hole mobility, photo‐responsivity, and photo‐detectivity) simultaneously. An improved carrier transport model in CH3NH3PbBr3 (MPB) single‐crystal thin‐film (SCTF) is proposed to elucidate the regulation mechanism of defects and carrier transport under electrical doping. These results show that the surface defect density can be effectively reduced by 47.49% under optimal electrical poling intensity (0.168 V µm−1), and photoluminescence intensity and carrier lifetime can be increased by 259% and 89.98%, respectively. Furthermore, planar MPB SCTF photodetector exhibits hole mobility increased by 14.97%, photo‐responsivity increased by 82.78%, and photo‐detectivity increased by 868% at 0.168 V µm−1. Particularly, a record photo‐detectivity of 3.53 × 1013 Jones is achieved under electrical doping. This study provides guidance for flexibly adjusting defect density and optimizing perovskite SCTFs light‐emitting/detecting bifunctional devices. [ABSTRACT FROM AUTHOR]

Atomically doping in thin film poses a significant challenge due to the potential for dopant precipitation caused by self‐purification effects. This challenge is particularly pronounced in the case of doping monolayers of photoluminescent transition metal dichalcogenides, where high energy barriers are also required to break the in‐plane bonds between the transition metal (TM) and chalcogen atoms. To address this issue, this study introduces hydroxide ions to adsorb onto the surface of WS2 monolayers. This results in a significant reduction in the formation energy of the TM─S bonds, enabling them to substitute for W sites and overcoming the self‐purification effect of WS2 monolayers. The in‐plane doping of TMs including Cr, Mn, Fe, Co, and Ni atoms is confirmed through precise atomic‐scale chemical imaging using scanning transmission electron microscopy with electron energy loss spectroscopy mapping. Photoluminescence measurements reveal that the band structure of WS2 monolayers can be systematically modulated by different doping metals, owing to their distinct atomic sizes. In addition, the atomically‐doped WS2 monolayers exhibit room‐temperature ferromagnetism, which has never been seen in pristine WS2 monolayers. The modulation of the band structure and the emergence of magnetism in TMs‐doped WS2 monolayers hold significant promise for optoelectronic and magnetoelectric applications. [ABSTRACT FROM AUTHOR]

Multi‐resonance (MR) based organoboron emitters exhibiting high‐efficiency narrowband thermally activated delayed fluorescence (TADF) have become a critical material component for constructing high‐performance organic light‐emitting diodes (OLEDs) with high color purity and high color gamut. However, most of the MR‐TADF devices suffer from severe efficiency roll‐off at high current density due to the relatively large singlet–triplet splitting energy, long excited state lifetime, and slow reverse intersystem crossing rate (kRISC). Herein, by utilizing a sulfur atom‐fused donor unit, 7H‐benzo[4,5]thieno[2,3‐b]carbazole, an organic boron emitter (BTC‐BNCz) capable of high efficiency and low efficiency roll‐off narrowband TADF emission is developed. Benefitting from the heavy atom effect of the sulfur atom, kRISC up to 1.6 × 105 s−1 is achieved, which could greatly reduce the undesired quenching effect. Consequently, the OLED using BTC‐BNCz as dopant exhibits high external quantum efficiency (EQE) of 27.0% with full width at half maximum (FWHM) of 35 nm. Moreover, by utilizing a TADF material with a high horizontal dipole ratio as assistant host, outstanding device performance is achieved with a maximum EQE of 35.2% and FWHM of 37 nm, featuring slow efficiency roll‐off. [ABSTRACT FROM AUTHOR]

For purely nitrogen‐based multi‐resonance emitters (N‐MR), strategies to integrate emission modulation with high color purity remain exclusive, especially in near‐ultraviolet (NUV) regions. Herein, it is demonstrated for the first time that rationally introducing weak intramolecular charge transfer (ICT) to the MR skeleton to modulate the emission from violet to deep‐blue while retaining high color purity is feasible. By replacing the middle phenyl moiety with the pyridine or benzonitrile unit in the solely nitrogen‐based violet MR skeleton of tDIDCz, two proof‐of‐concept emitters, Nm‐ICz and CNm‐ICz, emphasizing mixed excited states of localized excited (LE) transition from the original MR skeleton and emergent transition channel with charge‐transfer (CT) character, successfully realize bathochromic‐shift and polarity‐insensitive fluorescence from 395 nm to 404–407 and 419–421 nm, respectively, while retaining small full‐width at half‐maximums (FWHMs) of 28–37 and 33–43 nm (214‐281 and 237–310 meV). Furthermore, Nm‐ICz shows bright and violet electroluminescence (EL) spectrum with the peak at 412 nm, while CNm‐ICz shows high color purity deep‐blue EL spectrum with the peak at 427 nm, a small FWHM of 42 nm (286 meV), an ultralow y color coordinate of 0.027, and a maximum external quantum efficiency (EQEmax) of 3.7%. [ABSTRACT FROM AUTHOR]

Solely through‐space charge transfer (TSCT)‐type thermally activated delayed fluorescent (TADF) emitters exhibit low radiative decay rates (krs$k_{\rm{r}}^{\rm{s}}$), while solely through‐bond charge transfer (TBCT) type TADF emitters generally suffer from low reverse intersystem crossing (RISC) rates (kRISC). Here, PhCzSpiroS‐TRZ with versatile spiro‐heterocyclic architecture and an extra donor of 9‐phenyl‐9H‐carbazole are developed as emitter and ideal host for TADF‐ and TADF‐sensitized fluorescence (TSF) organic light‐emitting diodes (OLEDs) in detail. Abandoning solely TSCT or TBCT process, PhCzSpiroS‐TRZ with multiple charge transfer characteristic exhibits photoluminescence quantum yield of 96.3% and krs$k_{\rm{r}}^{\rm{s}}$ of 2.2 × 107 s−1, which is considerably higher among all the reported TSCT‐TADF molecules. Noticeably, state‐of‐the‐art blue OLEDs using PhCzSpiroS‐TRZ as emitter and sensitizer show maximum external quantum efficiencies (EQEs) of 33.6% and 32.8%, ranking among TADF materials for achieving EQEs >30% in both TADF‐ and TSF‐OLEDs. [ABSTRACT FROM AUTHOR]

Modulating the emission wavelength in the range of ultraviolet to deep‐blue with high color purity remains elusive. Herein, a versatile strategy is proposed from the perspective of rationally regulating nonbonding/π‐bonding character of frontier molecular orbitals to finely modulate emission colors while retaining superior color purity. By modifying the fused modes of indolo[3,2,1‐jk]carbazole (ICz) units, the proof‐of‐the‐concept emitters emphasize adjustable hybridization of nonbonding and π‐bonding characteristics, achieving a wide‐range color tuning range from ultraviolet (380 nm) to deep‐blue (428 nm) and small full‐width at half‐maximum (FWHM) of 8–33 nm (63–222 meV). Organic light‐emitting diodes based on the new emitter exhibit electroluminescence emission at 430 nm, a small FWHM of 44 nm (253 meV), maximum external quantum efficiency of 10.9%, and CIE color coordinates of (0.16, 0.05). The CIE coordinates are close to the National Television System Committee (NTSC) standard blue of (0.15, 0.06). [ABSTRACT FROM AUTHOR]

Developing innovative narrow‐band green‐emitting phosphors featuring low thermal quenching and eco‐friendliness for white light‐emitting diode (WLED) backlights is a pivotal challenge. Benefitting from narrowband and low toxicity of green‐emitting silanized carbon dots (Si‐CDs), an efficient confinement and protection strategy through embedding Si‐CDs in mesoporous aluminas (MAs) is proposed to construct MAs and Si‐CDs composites (Si‐CDs@MAs) with superior luminescence properties. Si‐CDs@MAs phosphor exhibits green emission at 526 nm with narrow full width at half maximum of 51 nm, zero‐thermal quenching even up to 423 K (104.1%@423 K of the emission peak intensity at 298 K), and the internal quantum efficiency of 64.46%. Compared with broad‐band yellow‐emitting solid‐state Si‐CDs (S‐Si‐CDs), the thermal stability, photostability, and water stability of Si‐CDs@MAs phosphor are remarkably improved due to surface protection. The WLED backlight is fabricated with optimized Si‐CDs@MAs phosphor, which shows high luminous efficacy of 117.43 lm W−1 and wide color gamut (107% NTSC). Furthermore, this work provides the design principles of realizing stable narrow‐band solid‐state fluorescence carbon dots, suggesting its great potential for wide‐color‐gamut display application. [ABSTRACT FROM AUTHOR]

Cr3+‐activated broadband near‐infrared (NIR) phosphors, featured by the octahedral coordination preference and strong absorption in visible (Vis) region, have great potential application in nondestructive assessment. It is still a challenge to develop Cr3+‐doped phosphors with the tetrahedrally coordinated Cr3+ NIR emission behavior and ultra‐wide Vis–NIR luminescence. Herein, an unusual NIR‐emitting Mg2Al4Si5O18:Cr3+ phosphor offers emission peak at 867 nm with full‐width at half‐maximum of 237 nm due to preferential occupation of the AlO4 tetrahedra by Cr3+ as demonstrated by structural and optical properties studies. Eu2+–Cr3+ energy transfer is proposed to induce ultra‐wide Vis–NIR Mg2Al4Si5O18:Eu2+,Cr3+ phosphors with more efficient NIR emission and lower thermal quenching behavior of Cr3+. The fabricated Vis–NIR phosphor‐converted light‐emitting diode is expected to be an alternative to halogen lamp in hyperspectral imaging. This work reveals the luminescence behavior of Cr3+ in tetrahedra and demonstrates the application of Mg2Al4Si5O18:Eu2+,Cr3+ phosphor in hyperspectral imaging, which will facilitate further research on NIR and Vis–NIR phosphors. [ABSTRACT FROM AUTHOR]

Generally, the charge transfer character of thermally activated delayed fluorescence (TADF) materials results in a long excitonic lifetime and broad‐band emission. With the combination of unity exciton utilization of TADF material and high radiative rate and narrow‐band emission of conventional fluorescence (CF) dopant, hyperfluorescence organic light‐emitting diodes (HF‐OLEDs) attract extensive attention in industry and academia recently. Till now, Dexter energy transfer (DET) from the triplet state of TADF assistant host to the dark triplet state of CF guest is the top‐drawer energy loss issue root in HF‐OLEDs. Herein, the energy loss of DET is blocked through one‐step substitution of TADF assistant host by electronically inert phenyl‐fluorene terminal for the first time. The blocking effect on DET process in HF‐OLEDs is investigated by means of photophysical characterization, theoretical calculation, device fabrication, and Monte Carlo simulation. The maximum external quantum efficiency of 18.1% with Commission Internationale de L'Eclairage coordinates of (0.61, 0.38) is achieved, which is on par with the state‐of‐the‐art efficiency for red HF‐OLEDs. This work presents a feasible design strategy for TADF assistant host aimed at achieving highly efficient HF‐OLEDs with narrow‐band emission. [ABSTRACT FROM AUTHOR]

Hot‐injection methods are widely used for the synthesis of colloidal perovskite nanocrystals (PeNCs). However, the long‐chain hydrocarbon solvents with alkene groups, such as octadecene (ODE), cannot be removed completely due to the strong van der Waals force between ODE and surface ligands as well as the large difference in the polarity with ethyl acetate, which hinders the charge transport characteristic of PeNCs and thus reduces the performance of PeNC‐based light‐emitting diodes (PeLEDs). Herein, an alkene‐free solvent‐assisted strategy is reported to synthesize high‐quality CsPbBr3 PeNCs in toluene and it is found that the alkene‐free solvent can significantly influence the morphology, composition, and optoelectronic properties of PeNCs. Compared to the traditional ODE solvent with alkene groups, toluene endows the higher solubility of precursors, which reduces the growth rate of PeNCs and allows sufficient time for the perovskite crystallization to suppress the bulk defects. Moreover, the similar polarity between toluene and ethyl acetate avoids long‐chain solvent residual on the PeNCs, thereby improving the charge transport characteristics. Making use of these PeNCs prepared with toluene solvent, the resulting PeLEDs present a peak external quantum efficiency of over 15%, 1.5‐fold higher than that of the device based on PeNCs that are prepared in ODE. [ABSTRACT FROM AUTHOR]

Due to the scarcity of blue color in the natural food palette, synthetic blue edible colorants are commonly used in daily life. With growing awareness of environmental hazards and potential side‐effect impacts of synthetic food colorants on customers' health, synthetic blue edible colorants are no longer a good choice. Here, a strategy of mixing two edible sub‐microspheres, mesoporous hollow TiO2 sub‐microspheres or SiO2 sub‐microspheres and cuttlefish ink particles, is reported to produce mass amorphous photonic structures (APSs) with structural color. The hues can be tuned by controlling the size of mesoporous hollow TiO2 sub‐microspheres, and the saturation is strongly related to the proportion of cuttlefish ink particles. Cytotoxicity assays and evaluation of bioaccessibility in the simulated human digestive system further prove the safety of the blue structural colorants. The blue structural colorants exhibit high color visibility, thermostability, and reliable food safety, which are promising properties for food, drugs, and cosmetics. [ABSTRACT FROM AUTHOR]

2D hybrid organic–inorganic perovskites (HOIPs) are highly responsive to external stimuli and therefore have application potential as sensing materials. Though their optical properties upon singular thermal or pressure stimulation have been recently investigated, their dual‐stimuli‐responsive behaviors have not yet been explored. Here, the dual‐stimuli‐responsive luminescence of a pair of new enantiomeric 2D Dion–Jacobson HOIPs, R+[(4‐aminophenyl)ethylamine]PbI4 and S‐[(4‐aminophenyl)ethylamine]PbI4, is reported. The photoluminescence results show that their 485 nm emissions can be red‐shifted by ≈6 nm upon heating, and further increased to 529 nm under pressure. Such dual‐stimuli‐responsive emissions expand their Commission Internationale de L'Eclairage coordinates successively from (0.140, 0.272) to (0.283, 0.473). Detailed structural analysis and first principles calculations reveal that the temperature‐ and pressure‐responsive behaviors arise from the predominant electron–phonon interactions over thermal expansion effect and pressure‐induced in‐plane PbI bond contraction, respectively. The findings open up a new pathway to successively tune the optical emission of 2D HOIPs via a dual‐stimuli‐responsive approach. [ABSTRACT FROM AUTHOR]

Assembly of 2D molecules into hierarchical structures opens new avenues for creating multifunctional materials, yet fabricating the optical materials with multiscale structural features, and extending functions in a controllable way remains a challenge. Here, an asynchronous liquid depositing strategy is introduced that enables the asymmetrical growth of 2D covalent organic frameworks (COFs) on a graphene substrate. This results in Janus composite (JC) materials with independently controlled mesoscopic features, such as the COF layer thickness (100–300 nm), and its nanoflake length (0–200 nm), and thickness (0–30 nm). The JCs exhibit impressive light coupling capabilities and display a wide range of angle‐independent structural colors. These colors can be dynamically and reversibly changed in 10 ms when exposed to volatile organic compounds (VOCs). They also demonstrate remarkable tailorability to form both random and ordered patterns which shows excellent information processing potential. These unique properties make JCs highly suitable as novel responsive optical devices for collecting and processing information about their surroundings, as demonstrated by visual and real‐time VOC monitoring and localization in both open and confined spaces. It is believed that the controlled assembly of 2D components into composites with well‐organized hierarchical structures will facilitate the future development of extraordinary materials with extensive applications. [ABSTRACT FROM AUTHOR]