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Aqueous zinc metal batteries (AZMBs) directly utilizing Zn metal anode have been regarded as a promising candidate for the next generation commercial batteries featuring high safety, high theoretical capacity, and appealing chemical stability. However, narrow electrochemical stability windows of aqueous electrolytes, uncontrolled dendrite and limited reversibility still plague its practical applications. Herein, we present a strategy via engineering dilute aqueous Zn(OTf)2 solutions electrolytes with a polyethylene glycol (PEG) network, which substantially decreases the activity of water molecules, and simultaneously enables smooth Zn deposition with a (002) textured and a favorable ZnF2-rich SEI. As a result, symmetric cells with PEG-H2O system show record high cyclic performance (9000 h and 8000 h at current densities of 1 and 2 mA cm−2, respectively), superior interfacial stability and dendrite-free morphology after repeated plating/stripping. Additionally, Zn||70%PEG||V2O5 full batteries also deliver a remarkable energy density of 324.3 W h Kg−1 at a power density of 466.9 W Kg−1 and maintain 84.3% of the capacity over 500 cycles at a high current density of 15 A g−1. All these comprehensive results demonstrate that this electrolyte structural engineering can provide a promising direction for designing high reversibility, long-cycling life aqueous Zn metal batteries.

Electrochromic batteries (EBs) have been developed as a technical breakthrough to solve the energy issues of storage and saving. Multivalent-ions (Zn2+, Mg2+ and Al3+) have recently demonstrated attractive properties for EBs due to their multiple-electron redox nature. However, still now, reported multivalent-ion EBs are typically assembled with a small-area metallic anode and a large-area electrochromic cathode. Non-uniformity of coloration and unstable metal plating/stripping hinder the developments of these devices. Additionally, insufficient energy/power density of EBs is a huge technical challenge needed to be overcome. In this work, we demonstrated a new aqueous aluminum-ion electrochromic full battery (AIEFB) to overcome the challenges. Systematic studies of density functional theory calculation, molecular dynamics simulation, electrochemical analysis, and mechanical measurements were conducted to optimize electrode materials and electrolyte. A water-in-salt (WIS) Al(OTF)3 electrolyte and a new electrochromic material couple of anodic amorphous WO3 (a-WO3) and cathodic indium hexacyanoferrate (InHCF) were exploited for AIEFB. The AIEFB demonstrated advantages of a high average discharge potential (1.06 V), an attractive energy density of 62.8 mWh m−2 at a power density of 2433.8 mW m−2, a high transmittance modulation of 63% at 600 nm, and a distinct transparent-to-deep blue coloration during the Al-ion shuttling processes.

The conformational distribution and mutual interconversion of thermally activated delayed fluorescence (TADF) emitters significantly affect the exciton utilization. However, their influence on the photophysics in amorphous film states is still not known due to the lack of a suitable quantitative analysis method. Herein, we used temperature-dependent time-resolved photoluminescence spectroscopy to quantitatively measure the relative populations of the conformations of a TADF emitter for the first time. We further propose a new concept of "self-doping" for realizing high-efficiency nondoped OLEDs. Interestingly, this "compositionally" pure film actually behaves as a film with a dopant (quasi-equatorial form) in a matrix (quasi-axial form). The concentration-induced quenching that may occur at high concentrations is thus expected to be effectively relieved. The "self-doping" OLED prepared with the newly developed TADF emitter TP2P-PXZ as a neat emitting layer realizes a high maximum external quantum efficiency of 25.4 % and neglectable efficiency roll-off.

As a potential low-cost and high energy density energy storage technology, rechargeable Mg batteries (RMBs) have shown renaissance in the last decade, since the first realization of Mg electrochemical deposition nearly a century ago. Based on the Chervel phase Mo6S8 cathode, metal Mg anode, and organohaloaluminate electrolyte, the first RMB prototype was constructed, and more and more investigations are being committed to advance RMB system after that. In this review, we first overview the current status and challenges of Mg-ion techniques. Recent developments on critical components of RMBs, i.e., cathode and anode materials, are then analyzed systematically. Based on these understandings on the state-of-the-art RMBs, potential improving strategies are proposed to provide insights on future development of RMBs.

Perovskite light-emitting diodes (LEDs) show great potential for next-generation lighting and display technology. Despite intensive studies on single-color devices, there are few reports on perovskite-based white LEDs (Pe-WLEDs). Here, an efficient Pe-WLED based on a blue perovskite and an orange phosphorescent emitter is reported for the first time. It is found that using a simple perovskite/phosphor bilayer emitting structure, there is inefficient energy transfer from the blue perovskite to the orange phosphor, leading to low efficiency and a significant color shift with driving voltage. We address this issue by introducing a quantum-well-like charge-confinement structure for enhancing carrier trapping and thus exciton formation in the phosphorescent emitter. As a result, a high external quantum efficiency of 10.81% is obtained. More interestingly, by tuning the dopant concentration of the phosphorescent emitter using this simple device structure, we can controllably get Pe-WLEDs with very stable white light for display applications or tunable color from warm white to daylight for lighting applications.

Martensite is a needle-shaped microstructure formed by a rapid, diffusionless transformation and significantly affects the mechanical properties of materials. Here, in two-dimensional ReS2 we show that martensite-like domain structures can form via a diffusionless transformation, involving small lattice deformations. By analyzing the strain distribution and topology of the as-grown chemical vapor deposition samples, we find that cooling-induced strain at the ReS2/substrate interface is responsible for the mechanical loading and is essential for martensite-like domain formation. Meanwhile, the effect of cooling rate, flake size and substrate on the microstructures revealed the mechanical origin of the transformation. The strain-induced lattice reconstructions are rationalized and possibly lead to ferroelastic effects. In view of the strong anisotropy in electronic and optical properties in two dimensional materials like ReS2, opportunities exist for strain-correlated micro/nanostructure engineering, which has potential use in next-generation strain-tunable devices. Two-dimensional materials have well-defined atomic-scale structure, which has the potential to be tuned by processing. Here, substrate-induced straining during the growth of ReS2 causes the formation of martensite-like domain structures.

In this work, an iron self-boosting polymer nanoenzyme was prepared by using pyrrole-3-carboxylic acid as a monomer and iron as an oxidizing agent via a simple and one-step method [hereafter referred to as FePPy nanoparticles (NPs)]. In fact, researchers previously paid negligible attention on the iron element during the polymerization reaction of polypyrrole, thus the intrinsically catalytic functions and enzymatic activities of the high iron content (wt %: 21.11%) are ignored and not fully explored. As expected, results demonstrate that the as-synthesized FePPy NPs can decompose H2O2 to generate hydroxyl radicals (•OH) which exhibit enzyme characteristics, further inducing a nonapoptotic ferroptosis pathway. Moreover, the nanoenzyme shows impressive photothermal properties which can accelerate the Fenton reactions to enhance ferroptosis. The combined photothermal and ferroptosis therapy of FePPy NPs was found to have high efficacy. With the properties of easy synthesis, high efficacy, and good biocompatibility, the FePPy NPs are considered as potential agents for cancer treatments.

Resonance interaction between a molecular transition and a confined electromagnetic field can lead to weak or strong light-matter coupling. Considering the substantial exciton–phonon coupling in thermally activated delayed fluorescence (TADF) materials, it is thus interesting to explore whether weak light-matter coupling can be used to redistribute optical density of states and to change the rate of radiative decay. Here, we demonstrate that the emission distribution of TADF emitters can be reshaped and narrowed in a top-emitting organic light-emitting device (OLED) with a weakly coupled microcavity. The Purcell effect of weak microcavity is found to be different for TADF emitters with different molecular orientations. We demonstrate that radiative rates of the TADF emitters with vertical orientation can be substantial increased in weakly coupled organic microcavity. These observations can enhance external quantum efficiencies, reduce efficiency roll-off, and improve color-purities of TADF OLEDs, especially for emitters without highly horizontal orientation., This work not only presents photophysical processes of thermally activated delayed fluorescent emitters in a weak Fabry-Pérot cavity, but also establishes a connection between emitter orientation and Purcell effect.

Extensive recent efforts have been put on the design of high-performance organic near-infrared (NIR) photothermal agents (PTAs), especially over NIR-II bio-window (1000-1350 nm). So far, the development is mainly limited by the rarity of molecules with good NIR-II response. Here, we report organic nanoparticles of intermolecular charge-transfer complexes (CTCs) with easily programmable optical absorption. By employing different common donor and acceptor molecules to form CTC nanoparticles (CT NPs), absorption peaks of CT NPs can be controllably tuned from the NIR-I to NIR-II region. Notably, CT NPs formed with perylene and TCNQ have a considerably red-shifted absorption peak at 1040 nm and achieves a good photothermal conversion efficiency of 42 % under 1064 nm excitation. These nanoparticles were used for antibacterial application with effective activity towards both Gram-negative and Gram-positive bacteria. This work opens a new avenue into the development of efficient PTAs.

Thermally activated delayed fluorescence (TADF)-sensitized fluorescent OLEDs are promising for next-generation OLEDs. However, the performance of these OLEDs with deviated CIE coordinates from the ...

Conventional photodetectors are usually “color blind” and require additional dispersive components or complicated structures to recognize colors. In this work, an organic photodetector (OPD) is designed with a layer of molybdenum(VI) oxide (MoO3) stacked on an organic donor/acceptor charge transfer interface. The band structure of the OPD is designed with multiple charge separation channels that can be activated/deactivated under reverse and forward biases. The combination of a high or low photocurrent under reverse and forward biases determines the colors of the received light, and that forms the heart of “non-color blind” ability to recognize light colors in the OPD. The energy structure and charge collection pathways in the OPD are investigated with biased external quantum efficiency (EQE), ultraviolet photoelectron spectroscopy (UPS) and current density–voltage (J–V) studies. The OPD with the ability of color and wavelength determination demonstrates its potential to recognize colors without using additional components and the dual mode operation enables it to work under different conditions via switching its detection ranges with bias voltages. This design principle can be utilized to fabricate multifunctional devices by simply selecting different donor–acceptor materials according to the desired detection ranges.

Triplet harvesting of organic materials is of great significance in many applications, including organic optoelectronic devices, anti-counterfeiting, and biological and chemical sensors. Aryl carbonyl-based luminescent materials have been widely studied in the above-mentioned fields because they possess intrinsic n–π* transitions as a result of the lone electron pairs of the carbonyl oxygen. Consequently, efficient intersystem crossing and reverse intersystem crossing can be achieved and triplet energy can be utilized through the narrow singlet–triplet offsets arose from the orthogonal overlaps between n and π* orbitals. It has also been revealed that they exhibit versatility in molecular tailoring and supramolecular engineering for various functional materials. This review presents a systematic summary of the recent research on aryl carbonyl (including moieties derived from aryl carbonyl) derivatives, with particular focus on their applications as electron acceptors, discussing the various strategies for the construction of luminescent materials with thermally activated delayed fluorescence and room-temperature phosphorescence, respectively. Finally, the perspectives and challenges concerning aryl carbonyl for triplet harvesting luminescent applications are also discussed.

II-VI semiconductor heterojunctions show huge potential for application in nanodevice fabrication due to their type-II alignments owing to the better spatial separation of electrons and holes. However, the hetero-epitaxial growth of high-quality heterostructures is still a challenge, especially for materials with large lattice mismatch. In this work, well-aligned single-crystalline ZnO/ZnS core/shell nanorod arrays were obtained by introducing an Al2O3 buffer layer. It is interesting that the nature of the ZnS layer varies with the thickness of the Al2O3 layer. When Al2O3 is less than 2 nm, the interaction between the substrate and epilayer is strong enough to penetrate through the buffer layer, enabling the growth of ZnS on Al2O3-coated ZnO nanorod arrays. On the basis of detailed characterization, a rational growth mechanism of the core/shell heterostructure is proposed, in which the Al2O3 interlayer can eliminate voids due to the Kirkendall effect around the interface and accommodate a misfit dislocation between the inner ZnO and outer ZnS, resulting in more sufficient strain relaxation in the epitaxy. In addition, cathodoluminescence measurements demonstrate that the optical properties of the ZnO/ZnS heterostructure could be effectively improved by taking advantage of the thin Al2O3. The I-V curves characterized by PeakForce tunneling atomic force microscopy reveal that the heterostructure shows a typical rectifying behavior and good photoresponse to ultraviolet light. These findings may provide a reasonable and effective strategy for the growth of highly lattice-mismatched heterostructure arrays buffered by the Al2O3 layer, broadening the options for fabricating heterojunctions and promoting their applications in optoelectronic devices.

Anatase TiO2 is a promising anode material for sodium-ion batteries (SIBs). However, its sodium storage mechanisms in terms of crystal structure transformation during sodiation/de-sodiation processes are far from clear. Here, by analyzing the redox thermodynamics and kinetics under near-equilibrium states, we observe, for the first time, that upon Na-ion uptake, the anatase TiO2 undergoes a phase transition and then an irreversible crystal structure disintegration. Additionally, unlike previous theoretical studies which investigate only the two end points of the sodiation process (i.e., TiO2 and NaTiO2), we study the progressive crystal structure changes of anatase TiO2 upon step-by-step Na-ion uptake (NaxTiO2, x = 0.0625, 0.125, 0.25, 0.5, 0.75, and 1) for the first time. It is found that the anatase TiO2 goes through a thermodynamically unstable intermediate phase (Na0.25TiO2) before reaching crystalline NaTiO2, confirming the inevitable crystal structure disintegration during sodiation. These combined experimental and theoretical studies provide new insights into the sodium storage mechanisms of TiO2 and are expected to provide useful information for further improving the performance of TiO2-based anodes for SIB applications.

High efficiency and stable blue phosphors have been a persistent pursuit in the field of organic light-emitting diodes (OLEDs). Bis-tridentate Ir(III) complexes are considered as promising alternatives because of their excellent emission efficiency and good photostability. However, the emission colors of photostable bis-tridentate Ir(III) emitters reported so far do not reach the deep blue region. Herein, fluorene is introduced in the design of blue bis-tridentate Ir(III) complexes. By modifying a fluorene-based dianionic chelate with tert-butyl, methoxy, pyrrolidinyl and triazolyl appendages, five blue emitting bis-tridentate Ir(III) phosphors were successfully designed and prepared. Emissions of the new phosphors exhibited a gradual blue shift from the sky blue to the deep blue region according to the electron donating abilities of the added substituents. A deep blue OLED was successfully fabricated based on Flu-4 and presented an excellent maximum external quantum efficiency of 22.3% with CIE coordinates of (0.17, 0.19), which are comparable to the state-of-the-art deep blue phosphors.

Developing highly efficient red thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge due to strict molecular design principles. In this contribution, two red emitters PXZ-AQPy and PXZ-AQPhPy with high structural rigidity and linear configurations are designed and synthesized based on phenoxazine (PXZ) as a donor and acenaphtho[1,2-b]quinoxaline (AQ) as an acceptor. Both molecules with horizontal orientation are endowed with TADF and aggregation-induced emission (AIE) properties. By elongating the acceptor segment via phenyl decoration, PXZ-AQPhPy exhibits higher horizontal ratios of the emitting dipole orientation (Θ‖ = 85%), while the emission characteristics are almost unaltered. Consequently, the PXZ-AQPhPy based device achieves a high external quantum efficiency of 19.6% with an emission peak at 610 nm. This work provides a simple and effective design strategy to selectively promote the horizontal orientation of red TADF emitters.

The LiF-rich solid electrolyte interphase (SEI) is an emerging research hotspot to improve battery performance. Its high Li-ion conductivity and high interfacial energy result in fast lithiation/de-lithiation in electrode materials while at the same time protect materials from pulverization. Currently, the developed LiF-rich SEI fabrication methods are based on electrolyte decomposition upon cycling, but so far have only been applied to Li metal or Si anodes. Furthermore, the influences of LiF on the electrochemical behavior of the electrolyte are not fully understood. Here, a new pre-coating approach is proposed to fabricate a conformal LiF layer on both anode and cathode materials (silicon suboxide (SiOx) and LiNi0.8Co0.1Mn0.1O2 (NCM811) as examples). LiF assisted the increase in the specific capacity of a SiOx electrode from 301 to 1034 mA h g−1 after 100 cycles at 500 mA g−1. In addition, a full cell assembled with a prepared anode (SiOG@LiF3) and cathode (NCM811@LiF3) showed outstanding cycling stability. Combining density functional theory (DFT) calculation with SEM and XPS characterization revealed for the first time that the pre-coating LiF layer had a strong preferential adsorption of LiPF6 molecules on the surface, leading to the formation of inorganic-rich SEI during cycling; thereby enabling a fast Li-ion uptake/removal process and improving the electrode integrity.

Developing red thermally activated delayed fluorescence (TADF) emitters for high-performance OLEDs is still facing great challenge. Herein, three red TADF emitters, pDBBPZ-DPXZ, pDTBPZ-DPXZ, and oDTBPZ-DPXZ, are designed and synthesized with same donor-acceptor (D-A) backbone with different peripheral groups attaching on the A moieties. Their lowest triplet states change from locally excited to charge transfer character leading to significantly enhance reverse intersystem crossing process. In particular, oDTBPZ-DPXZ exhibits efficient TADF feature and exciton utilization. It not only achieves an external quantum efficiency (EQE) of 20.1 % in red vacuum-processed OLED, but also realize a high EQE of 18.5 % in a solution-processed OLED, which is among the best results in solution-processed red TADF OLEDs. This work provides an effective strategy for designing red TADF molecules by managing energy level alignments to facilitate the up-conversion process and thus enhance exciton harvesting.

Summary With amazing progress in the state-of-the-art perovskite solar cells (PSCs) fabricated by laboratory-scale spin-coating methods, upscaling the PSCs via printing friendly techniques is becoming more and more important toward the future deployment of large-scale and stable perovskite modules. Here, we demonstrate the room-temperature meniscus coating of high-quality perovskite films incorporated with a multifunctional sulfobetaine-based zwitterionic surfactant. Systematic in situ studies uncover the perovskite crystallization pathway and emphasize the surfactant’s synergistic role in film construction, crystallization kinetics modulation, defect passivation, and moisture barrier protection. This strategy is applicable across perovskite compositions and device architectures with the enhanced power conversion efficiencies up to 22%. Upscaling the device area to 0.8 cm2 has negligible deterioration in the performance. This represents one of the highest records for the upscaling coated PSCs, not limited in room-temperature coated PSCs. In addition, this approach significantly improves the stability of perovskite films and devices under different aging conditions.

Three donor–acceptor–donor molecular emitters have been designed by taking triphenylamine or N-phenylcarbazole as the donor and maleimide or phenyl maleimide as the acceptor, in which the highest o...

Energy offset at the donor (D)/acceptor (A) interface plays an important role in charge separation in organic photovoltaics. Its magnitude determines the charge separation process under illumination. Extensive studies have been carried out for elucidating the charge transfer (CT) process at different D/A junctions. These works lead to two different views: upon photoexcitation, energies would be (1) consumed in molecular polarization and orientation such that those opposite charges would overcome mutual Coulombic attractive potential at the interface and (2) spent on promoting charges to high-lying delocalized energy states (i.e., hot states), which is necessarily important prior to charge separation. Under these two scheme of studies, the electronic structures and the charge behaviors at the D/A interface should be different under photoexcitation, yet there is so far no direct experimental approach for probing the changes in electronics structures (i.e., Fermi level, vacuum level, frontier molecular orbitals, etc.) upon photoexcitation. Herein, a modified photoelectron spectroscopy (PES) system with an additional solar simulator is used to study the charge distributions and electronic interactions for a standard D/A heterojunction (i.e., copper phthalocyanine (CuPc)/ fullerene (C60)) under photoexcitation. CT states formed as a result of photon energy transfer at the CuPc/C60 junction. Subsequent superpositions of charge transfer and electron polarization effects increase the D/A energy level offsets from 0.75 (ground state measured in the dark) to 1.07 eV (high-lying state measured upon illumination). We showed that there is excess energy consumed for a subtle change in the energy level alignment of the CuPc/C60 junction under illumination, suggesting a new insight for the energy loss mechanism during the photocharge generation processes.

Solar water evaporation has been considered as a promising technique to harvest solar energy for practicable water evaporation. While different classes of materials have been exploited as solar abs...

Effective multimodality phototheranostics under deep-penetration laser excitation is highly desired for tumor medicine, which is still at a deadlock due to lack of versatile photosensitizers with absorption located in the long-wavelength region. Herein, we demonstrate a stable organic photosensitizer nanoparticle based on molecular engineering of benzo[c]thiophene (BT)-based photoactivated molecules with strong wavelength-tunable absorption in the near-infrared region. Via molecular design, the absorption and singlet oxygen generation of BT molecules would be reliably tuned. Importantly, the nanoparticles with a red-shifted absorption peak of 843 nm not only show over 10-fold reactive oxygen species yield compared with indocyanine green but also demonstrate a notable photothermal effect and photoacoustic signal upon 808 nm excitation. The in vitro and in vivo experiments substantiate good multimodal anticancer efficacy and imaging performance of BT theranostics. This work provides an organic photosensitizer nanoparticle with long-wavelength excitation and high photoenergy conversion efficiency for multimodality phototherapy.

Maintaining the stability of tin halide perovskites is a major challenge in developing lead-free perovskite solar cells (PSCs). Adding extra SnX2 (X = F, Cl, or Br) in the precursor solution to inh...

Porous boron nitride (BN) materials have been considered as a promising material for CO₂ capture and storage. It was found that the Cu²⁺ ion can modify the nucleation mechanism during the synthetic reaction between boric acid and melamine leading to the formation of Cu-loaded BN nanofibers with uniform and smaller diameter. Interestingly, the introduction of Cu was found to dramatically enhance the CO₂ adsorption capacity of the BN nanofibers from 1.34 to 2.77 mmol g–¹ (at 1 bar, 273 K). The Cu-loaded BN nanofiber not only shows a CO₂ adsorption capacity comparable to those of state-of-the-art BN-based CO₂ absorbents but also shows unprecedented high recyclability for repeated uses. The mechanisms of the copper-induced CO₂ adsorption capacity enhancement were investigated with density-functional theory calculations. It was found that the incorporation of Cu can change the electron transfer between porous BN and CO₂ to promote the affinity and adsorption capacity of CO₂.

Fluorescent carbon nanodots (CNDs) have exhibited attractive potential for biomedical applications due to their intriguing luminescent properties and good biocompatibility. One interesting properties of CNDs is that they typically show different emission colors upon optical excitation using different wavelengths. However, it is still a challenge to obtain emissions covering the entire visible spectrum with comparable intensity with only one type of CND. Herein, CNDs with tunable full-color luminescence is successful prepared by a solvothermal approach, show broad absorption (200–700 nm) and fluorescence emission (nearly cover the entire visible region: from 400 to 700 nm) with comparable fluorescence intensities. The oxidation (o-CNDs) and reduction (r-CNDs) of CNDs surface would lead to the shifting of photoluminescence band into blue/green and red-light region, respectively. Further spectroscopic analyses and structural characterizations of CNDs (pristine state), o-CNDs (oxidation state) and r-CNDs (reduction state) demonstrate that O-related defect states (C O) and N-related defect states (C N) on surface of CNDs should be responsible for blue/green and red fluorescence emissions, respectively. Moreover, the CNDs are found to be biocompatible, as verified by in vitro cells assay and in vivo histological analysis. In vivo fluorescence imaging assay demonstrates that CNDs can be excreted through intestine and bladder system. The tunable full-color emission, good biocompatibility and metabolism suggest that the CNDs are promising fluorescent probes for biomedical applications.

MXenes, a new family of two-dimensional materials, are also known as transition metal carbides and nitride, with a general formula of M n +1X n T x (n = 1–3). Their inherent metallic conductivity and hydrophilic nature endow MXenes with fascinating physicochemical properties (optical, electronic, magnetic, light-to-heat conversion. etc.). The ultrathin layer structure and photothermal property attract many interests in biomedical applications, especially as phototherapeutic agents for cancer treatment. In this review, we summarize the recent progress of MXenes in the field of photothermal therapy and highlight the crucial biotic index for their preparation and evaluation. First, we introduce the main strategies for the preparation and surface modifications of biologically applied MXenes. Then, representative cases in the field of MXene-based photothermal application, such as photothermal therapy, synergistic therapy, and targeting treatments, are reviewed. Finally, the cytotoxicity and in vivo long-term biosafety are introduced. We also propose the underlying challenges and perspectives for MXene applications in terms of photothermal therapy.

A novel light-emitting material, 4-(4-diphenylaminophenyl)-benzo[d,e]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one (4-TPA-BBI) is synthesized and characterized. 4-TPA-BBI exhibits excellent polymorphis...

Perovskite is emerging as a novel emitter in solution-processed light-emitting diodes (LEDs). In these LEDs, morphology, especially the grain size of perovskite, plays a key role in determining electroluminescence performance. Several studies have shown that sizes of the perovskite grains can be controlled by the contact angle between the perovskite solution and the substrate. In this work, we found that in the quasi-two-dimensional (2D) system, the perovskite grain size can be substantially refined when there are hydrogen bonding between the perovskite's organic spacer and the substrates. In fact, for quasi-2D perovskite, with the presence of such hydrogen bond, its effects on the perovskite grain size overshadow the contact angle's effect. We demonstrated that perovskite with refined grains can form amine- or carbazole-based polymers which can form N···H hydrogen bonding with the perovskite's organic spacer. Using these polymers as hole-transporting layers on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, external quantum efficiency of CsPbBr3-based LEDs can be enhanced from 1.5 to 10.0% without passivation treatment. This work suggests that bonding between perovskite precursors and the substrate can have significant influence on the morphology of the final perovskite grains and their optoelectronic performance.

Thermally activated delayed fluorescence (TADF) emitters generally require good separation of highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) overlaps to minimize the singlet–triplet energy offset. Observations of excellent TADF performance in several planar emitters with large HOMO–LUMO overlaps are counter-intuitive and not fully explained. To understand this, we prepared two isomeric TADF molecules, 7-methyl-2-(10H-phenoxazin-10-yl)-5H-pyrano[4,3-b]pyridin-5-one (PXZ-PPO) and 2-methyl-7-(10H-phenoxazin-10-yl)-4H-benzo[d][1,3]oxazin-4-one (PXZ-BOO). PXZ-BOO has a stable highly-twisted configuration with a small HOMO–LUMO overlap leading to good TADF performance as expected. PXZ-PPO has a stable nearly-planar form and a large HOMO–LUMO overlap and is not expected to give TADF. While the solid crystal of PXZ-PPO only shows conventional fluorescence at 420 nm, its diluted solution is dominated by TADF at 610 nm. With a combined experimental and theoretical approach, PXZ-PPO is shown to have a stable nearly-planar form and a metastable highly-twisted form in the ground state. While the highly-twisted form only has a small population (

Exploiting high-performance non-doped organic light-emitting diodes (OLEDs) is a step towards future commercial application requirements, but great challenges remain due to quenching related to intermolecular triplet interaction. In this work, a novel strategy of exploiting high-performance non-doped electroluminescence via tuning intermolecular hydrogen bonding is demonstrated. Suitable intermolecular hydrogen bonding enables formation of a 3D supramolecular framework, which not only evidently restricts the nonradiative process and suppresses the triplet exciton quenching caused by π–π stacking of triplets, but also favors the horizontal molecular orientations especially in their non-doped states. The non-doped OLED based on the thermally activated delayed fluorescence emitter mTPy-PXZ with such suitable intermolecular hydrogen bonds exhibits the state-of-the-art performance with maximum external quantum efficiency of up to 23.6% with only 7.2% roll-off at 1000 cd m−2. Moreover, it is the first report that the performance of an OLED with a non-doped emitting layer can surpass its corresponding optimized doped device. It is believed that this hydrogen bond-modulated mechanism can not only provide a new pathway for designing emitters for high-performance non-doped organic electroluminescence, but also has great potential in other solid-state luminescence applications.

N-Borylated emitters bearing both boron dimesityl acceptor (Mes)2B and phenoxazine or acridine donors are a class of efficient TADF emitters; however, switching to a carbazole donor nullifies the TADF characteristics. This work is targeted at improving the TADF characteristics of the carbazole based (Mes)2B emitters by introducing up to two methoxy substituents at the carbazoles. We hereby report the design and synthesis of three methoxy substituted carbazoles (Cz-1, Cz-2 and Cz-3) and the corresponding directly N-borylated emitters, CzBM-1, CzBM-2 and CzBM-3. Moreover, a p-phenylene spacer was also introduced between the (Mes)2B unit and carbazole, giving CzPBM-2 and CzPBM-3. As confirmed by the bi-exponential transient decay analyses, all title compounds exhibit prominent TADF character, while the parent molecules CzBM-0 and CzPBM-0 without methoxy groups show no TADF characteristics. The results manifest the importance of the donor strength of substituents and degrees of spatial orthogonality in harnessing the charge transfer properties, minimalizing the S1–T1 energy gap and facilitating the reverse intersystem crossing process. OLED devices with doped CzBM-2 and CzPBM-3 emitters exhibited a maximum external quantum efficiency of 12.5% and 13.3%, respectively, confirming the potential of methoxy substituents in improving their TADF characteristics.

Photoluminescence quantum yield (PLQY) and the reverse intersystem crossing (RISC) process are critical for next-generation highly efficient organic light-emitting diodes (OLEDs). However, it is not easy to simultaneously obtain high PLQY and fast RISC, especially in TADF emitters with twisted donor–acceptor structures due to their conflicting requirements for wave function overlapping. Herein, based on a rigid planar dibenzo[a,c]phenazine (DPPZ) unit as an acceptor, four emitters (isomers of DMAC-11-DPPZ and DMAC-10-DPPZ, and isomers of PXZ-11-DPPZ and PXZ-10-DPPZ) with 9,9-dimethylacridine (DMAC) and 10H-phenoxazine (PXZ) as donors substituted via 11- and 10-positions were designed and synthesized to balance the wave function overlapping and explore the relationship between their structures and luminescence properties. Photophysical characterization and theoretical calculations suggest small energy gaps (ΔEST) featuring fast RISC rates in all these compounds. Meanwhile, DMAC-11-DPPZ and PXZ-11-DPPZ achieve higher PLQYs due to the largely suppressed non-radiative transition as revealed by the decreased Huang–Rhys factors. As a result, high external quantum efficiencies (EQEmax) of 23.8% for DMAC-11-DPPZ and 13.7% for PXZ-11-DPPZ are obtained. This work provides a promising strategy to improve the PLQY of TADF materials by adjusting the substituted site, and also shows the potential of phenazine derivatives for OLED applications.

The electrocatalytic nitrogen reduction reaction (e-NRR), an eco-friendly and economical approach to convert nitrogen to ammonia under mild conditions, has received widespread attention in recent years. Defect engineering has been illustrated to be an effective strategy to improve the catalytic activity and selectivity of electrocatalysts via changing the electronic states as well as creating additional active sites for reduction reactions. Thus far, various approaches have been adopted to tune the physical and chemical properties of catalyst materials by means of inducing defects of different types and varying their concentrations or locations in host materials. In this review, the mechanisms and design principles of defective electrocatalysts for the NRR are introduced, and the refined synthesis and characterization techniques of defect engineering are systematically summarized. Based on the recent advances in defect engineering of electrocatalysts for the NRR, the roles of various defect states, such as vacancies and the amorphous phase, in the catalytic enhancement mechanism are comprehensively discussed. Finally, perspectives on the challenges and opportunities in developing new cost-effective and high-efficiency NRR catalysts for practical applications are outlined.

Thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) have attracted much recent attention for their capabilities to utilize triplet excitons for emission. Herein, we demonstrate a strategy for switching between intermolecular TADF and RTP through rational structure modulation and crystal engineering with two newly designed organic AIEgens, namely (4-(9H-carbazol-9-yl)phenyl) (dibenzo[b,d]thiophen-2-yl)methanone (CTM) and (4-(3,6-di-tert-butyl-9H-carbazol-9-yl) phenyl) (dibenzo[b,d]thiophen-2-yl) methanone (tCTM). Both materials exhibit intramolecular TADF and intermolecular TADF/RTP dual emission in single crystals. High contrast mechanochromic luminescence (MCL) was unveiled due to the polymorphism of both emitters in aggregated states. Using these materials as emitters, we demonstrate for the first time, such dual TADF–TADF/RTP emissions can be exploited to obtain white light organic light-emitting diodes with high color rendering indexes.

Rational manipulation of energy utilization from excited-state radiation of theranostic agents with a donor–acceptor structure is relatively unexplored. Herein, we present an effective strategy to tune the exciton dynamics of radiative excited state decay for augmenting two-photon nanotheranostics. As a proof of concept, two thermally activated delayed fluorescence (TADF) molecules with different electron-donating segments are engineered, which possess donor–acceptor structures and strong emissions in the deep-red region with aggregation-induced emission characteristics. Molecular simulations demonstrate that change of the electron-donating sections could effectively regulate the singlet–triplet energy gap and oscillator strength, which promises efficient energy flow. A two-photon laser with great permeability is used to excite TADF NPs to perform as theranostic agents with singlet oxygen generation and fluorescence imaging. These unique performances enable the proposed TADF emitters to exhibit tailored balances between two-photon singlet oxygen generation and fluorescence emission. This result demonstrates that TADF emitters can be rationally designed as superior candidates for nanotheranostic agents by the custom controlling exciton dynamics., Exciton dynamics can be manipulated rationally in the design of TADF materials for nanotheranostics. Regulating the ΔEST and f promises efficient energy flow for tailoring balances between singlet oxygen generation and fluorescence emission.

Achieving efficient solar steam generation under natural sunlight has huge potential for sewage purification and seawater desalination. Plasmonic resonance has been extensively exploited for enhancing and extending the range of optical absorption. Until now, most reported broadband plasmonic solar absorbers have been designed by compact aggregation or engineering plasmonic architectures. In this work, we develop a new plasmonic absorber using gold nanostructures with the shape of a trepang (nano-trepang). By rationally regulating anisotropy at the single nanoparticle level, the nano-trepang shows good optical absorption over the entire solar spectrum (92.9%) with no requirement of engineering nanoparticle aggregation or constructing plasmonic architectures. The nano-trepang was then loaded into a polymeric aerogel and the network showed an excellent solar-to-vapor energy conversion efficiency of 79.3%. Under 1 sun AM1.5 G irradiation, a stable solar evaporation rate of 2.7 kg m−2 h−1 can be achieved, with high performance anti-salt precipitation in practical seawater steam generation. This work shows a broadband plasmonic absorber with aggregation-independent performance for highly efficient solar stream generation and provides a new strategy for practical solar desalination.

Novel charge transport properties distinguished from their parental materials are intriguing features of charge transfer complexes (CTCs). In this work, co-evaporated molybdenum(VI)oxide and sexithiophene (MoO3 : 6T) CTC thin film is prepared and its electron and hole transport properties are studied. While the MoO3 : 6T CTC material shows both electron and hole transport, detailed changes in molecular orbital hybridization are further studied under an external stimulus. Using a simple rubbing process, the intermolecular interaction of the CTC material can be tuned such that changes in optical properties, vibrational modes, chemical states and electronic structures are observed. These changes in properties and charge transport behaviors enable us to understand the influences of CTC frontier molecular orbitals (FMOs) and their degree of coupling on the charge transport properties. This work provides insight into the understanding of the intermolecular interactions and their influence on the charge transport properties of thin film CTCs.

Possessing high photoluminescence quantum yield (PLQY) and fast reverse intersystem crossing (RISC) process are critical for obtaining efficient thermally activated delayed fluorescence (TADF) emitters. Herein, two donor–spacer–acceptor molecules, namely, 4-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-2,6-dimethylpyridine-3,5-dicarbonitrile (Me-DMAC) and 4-(4-(10H-phenoxazin-10-yl)phenyl)-2,6-dimethylpyridine-3,5-dicarbonitrile (Me-PXZ), were developed via a double-twist design strategy. The large hindrance induces a twisted geometry, leading to small ΔEST values and fast RISC processes. The time-resolved photophysical measurements revealed the TADF emissions of these pyridine-3,5-dicarbonitrile-based molecules in doped thin films. High external quantum efficiency (EQE) values of 25.8% and 21.1% were achieved in organic light-emitting diodes (OLEDs) using green Me-DMAC and yellow Me-PXZ dyes, respectively, as emitters.

Bismuth (Bi) is a promising alloy-type material for potassium-ion batteries (KIBs). However, its large volume variation during the cycling process remains a great challenge to its practical application. Here, a one-step approach was developed to synthesize a novel Bi-based composite structure comprising Bi nanorod networks confined in a N, S co-doped carbon matrix (Bi∈NS–C). As an anode, the Bi∈NS–C structure successfully integrated the merits of the micro-sized N, S co-doped carbon matrix, which functioned concurrently as a conductive framework and a robust buffer for large volume variation, and the network structure of Bi nanorods which enhanced the reaction kinetics and accommodated the large strain originating from the alloying/dealloying process. As a result, the Bi∈NS–C electrodes exhibited an excellent overall performance, i.e., high rate capabilities of 338 mA h g−1 and 289 mA h g−1 at current densities of 0.5 and 6 A g−1, respectively, and outstanding long-term cycling stability with 91% capacity retention at 5 A g−1 after 1000 cycles. Furthermore, a full KIB with hexacyanoferrate as the cathode and Bi∈NSC as the anode was assembled, which was demonstrated to be able to deliver a decent energy density of 295 W h kg−1 and superior cycling stability with 83% capacity retention after 800 cycles.

Direct torque control (DTC) suffers from flux droop owing to the long zero-voltage vectors at low motor speeds. Previous studies were able to attain flux regulation by imposing the continuous switching of forward and reverse active-voltage vectors by causing torque overshoots in the torque hysteresis bands (THBs). This led to an excessive increase in the switching frequency and larger torque and current ripples, thus reducing the drive efficiency. In this paper, a modified flux regulation method is proposed for the classical DTC using a single THB when flux droop occurs in a low-rotor-speed range. The proposed method can protect the DTC from flux droops at low speeds by reducing the duration of zero-voltage vectors and minimizing the number of reverse-voltage vectors. In addition, the proposed strategy is efficient in reducing torque and current ripples while operating at low motor speeds. Furthermore, a significant reduction in the switching frequency is obtained. The effectiveness of the proposed strategy is confirmed by simulation and experimental results.

We developed a biodegradable photothermal therapeutic (PTT) agent, π-conjugated oligomer nanoparticles (F8-PEG NPs), for highly efficient cancer theranostics. By exploiting an oligomer with excellent near-infrared (NIR) absorption, the nanoparticles show a high photothermal conversion efficiency (PCE) up to 82%, surpassing those of reported inorganic and organic PTT agents. In addition, the oligomer nanoparticles show excellent photostability and good biodegradability. The F8-PEG NPs are also demonstrated to have excellent biosafety and PTT efficacy both in vitro and in vivo. This contribution not only proposes a promising oligomer-based PTT agent but also provides insight into developing highly efficient nanomaterials for cancer theranostics.

The benchmark tin oxide (SnO2) electron transporting layers (ETLs) have enabled remarkable progress in planar perovskite solar cell (PSCs). However, the energy loss is still a challenge due to the lack of “hidden interface” control. We report a novel ligand-tailored ultrafine SnO2 quantum dots (QDs) via a facile rapid room temperature synthesis. Importantly, the ligand-tailored SnO2 QDs ETL with multi-functional terminal groups in situ refines the buried interfaces with both the perovskite and transparent electrode via enhanced interface binding and perovskite passivation. These novel ETLs induce synergistic effects of physical and chemical interfacial modulation and preferred perovskite crystallization-directing, delivering reduced interface defects, suppressed non-radiative recombination and elongated charge carrier lifetime. Power conversion efficiency (PCE) of 23.02% (0.04 cm2) and 21.6% (0.98 cm2, VOC loss: 0.336 V) have been achieved for the blade-coated PSCs (1.54 eV Eg) with our new ETLs, representing a record for SnO2 based blade-coated PSCs. Moreover, a substantially enhanced PCE (VOC) from 20.4% (1.15 V) to 22.8% (1.24 V, 90 mV higher VOC, 0.04 cm2 device) in the blade-coated 1.61 eV PSCs system, via replacing the benchmark commercial colloidal SnO2 with our new ETLs.

Enhancing the reverse intersystem crossing (RISC) process of thermally activated delayed fluorescent (TADF) emitters is an effective approach to realize efficient organic light-emitting diodes (OLEDs) with low efficiency roll-off. In this work, we designed two novel TADF emitters, SAT-DAC and SATX-DAC, via a spiro architecture. Efficient maximum external quantum efficiencies (EQEs) of 22.6 and 20.9% with reduced efficiency roll-off (EQEs of 17.9 and 17.0% at 1000 cd m-2) were achieved via a "two-RISC-channel" strategy. X-ray diffraction shows close donor (D)/acceptor (A) spacing and suitable D/A orientation in crystals of the two emitters favoring both intra- and intermolecular through-space charge transfer (TSCT) processes. Transient photoluminescence decay measurements show that both emitters have two RISC channels leading to kISCT exceeding 106 s-1. These results suggest that the "two-RISC-channel" design can be a novel approach for enhancing performance of TADF emitters, in particular at high excitation densities.

Highly twisted electron donor (D)-electron acceptor (A)-type thermally activated delayed fluorescence (TADF) emitters can achieve high efficiency while suffering from serious structural relaxations and broad emissions. Multiple resonance (MR)-type TADF emitters can realize narrow emission. However, until now, only a few efficient MR-emitting cores are reported and custom tunning of their emission color remains a major challenge in their wider applications. In this work, by combining the conventional TADF and MR-TADF designs, we demonstrate that color tuning and narrowing the spectral width of conventional TADF emission can be easily achieved simultaneously. We select a prototypical carbonyl (C═O)/N-based MR core as a backbone and attach it with D segments of different electron-donating abilities and numbers to obtain three different TADF emitters with emissions from sky blue to green and orange-red while maintaining the narrow emission of the original MR core. The corresponding sky blue, green, and orange-red organic light-emitting diodes achieve maximum external quantum efficiencies of 20.3, 27.3, and 26.3%, respectively, and narrow full widths at half-maximum all below 0.28 eV. These results provide a new molecular design strategy for developing narrowband TADF emitters with easily tunable emissions covering the full visible range.

Solar steam generation is considered as an efficient way for addressing water shortage issues via seawater desalination and wastewater purification. In a solar evaporator, an absorber would convert optical energy to heat for evaporating nearby water. In this process, many low-boiling-point contaminants can also be evaporated along with water steam, which compromises the effectiveness of purification. There is, so far, no study on the removal of such low-boiling-point contaminants such as organic pesticides in wastewater. To address this problem, we demonstrate a versatile carbon hybrid aerogel (CHA) as a solar powered water purification platform. With an elaborate absorber design, the maximum solar evaporation rate of 2.1 kg m-2 h-1 is achieved under 1 sun illumination. More importantly, CHA can effectively suppress the evaporation of low-boiling-point contaminants including common pesticides and mercury ion via its strong adsorption and retention effect. Synergetic steaming and the adsorption of CHA will inspire more paradigms of solar steam generation technologies for applications relevant to detoxification and water remediation.