Two‐dimensional metal–organic frameworks (2D MOFs) can be used as the cathodes for high‐performance zinc‐ion battery due to their large one‐dimensional channels. However, the conventionally poor ...electrical conductivity and low structural stability hinder their advances. Herein, we report an alternately stacked MOF/MX heterostructure, exhibiting the 2D sandwich‐like structure with abundant active sites, improved electrical conductivity and exceptional structural stability. Ex situ characterizations and theoretical calculations reveal a reversible intercalation mechanism of zinc ions and high electrical conductivity in the 2D heterostructure. Electrochemical tests confirm excellent Zn2+ migration kinetics and ideal pseudocapacitive behaviors. As a consequence, Cu‐HHTP/MX shows a superior rate performance (260.1 mAh g−1 at 0.1 A g−1 and 173.1 mAh g−1 at 4 A g−1) and long‐term cycling stability of 92.5 % capacity retention over 1000 cycles at 4 A g−1.
A MOF/MXene heterostructure, which exhibits a molecular‐scale hybridized MOF (Cu‐HHTP) and MX (V2CTx MXene) nanosheets, is successfully synthesized. The results show that the Zn2+ storage capability of such a 2D heterostructure is boosted by enhancing the structural stability, electrical conductivity, and the utilization of active sites.
White organic light‐emitting diodes (WOLEDs) are superior to traditional incandescent light bulbs and compact fluorescent lamps in terms of their merits in ensuring pure white‐light emission, ...low‐energy consumption, large‐area thin‐film fabrication, etc. Unfortunately, WOLEDs based on multilayered or multicomponent (red, green, and blue (RGB)) emissive layers can suffer from some remarkable disadvantages, such as intricate device fabrication and voltage‐dependent emission color, etc. Single molecules, which can emit white light, can be used to replace multiple emitters, leading to a simplified fabrication process, stable and reproducible WOLEDs. Recently, the performance of WOLEDs by using single molecules is catching up with that of the state‐of‐the‐art devices fabricated by multicomponent emitters. Therefore, an increasing attention has been paid on single white‐light‐emitting materials for efficient WOLEDs. In this review, different mechanisms of white‐light emission from a single molecule and the performance of single‐molecule‐based WOLEDs are collected and expounded, hoping to light up the interesting subject on single‐molecule white‐light‐emitting materials, which have great potential as white‐light emitters for illumination and lighting applications in the world.
Different types of single organic white‐light‐emitting molecules and their light‐emitting devices are summarized. The blue and complementary emissions are ascribed to the monomers of molecules and their intra‐ or intermolecular interactions, respectively. The devices based on these molecules exhibit high efficiencies and color stabilities, affording a convenient approach to light up the white organic light‐emitting diodes.
Sn–Pb mixed perovskites with bandgaps in the range of 1.1–1.4 eV are ideal candidates for single‐junction solar cells to approach the Shockley–Queisser limit. However, the efficiency and stability of ...Sn–Pb mixed‐perovskite solar cells (PSCs) still lag far behind those of Pb‐based counterparts due to the easy oxidation of Sn2+. Here, a reducing agent 4‐hydrazinobenzoic acid is introduced as an additive along with SnF2 to suppress the oxidation of Sn2+. Meanwhile, a vertical Pb/Sn compositional gradient is formed spontaneously after an antisolvent treatment due to different solubility and crystallization kinetics of Sn‐ and Pb‐based perovskites and it can be finely tuned by controlling the antisolvent temperature. Because the band structure of a perovskite is dependent on its composition, graded vertical heterojunctions are constructed in the perovskite films with a compositional gradient, which can enhance photocarrier separation and suppress carrier recombination in the resultant PSCs. Under optimal fabrication conditions, the Sn–Pb mixed PSCs show power conversion efficiency up to 22% along with excellent stability during light soaking.
4‐Hydrazinobenzoic acid is introduced to enhance the efficiency and stability of Sn–Pb mixed‐perovskite solar cells. Moreover, a vertical compositional gradient with a continuous change of the Pb/Sn ratio is found in the Sn–Pb mixed‐perovskite films, leading to graded heterojunctions that are beneficial for photocarrier separation. The resultant devices show a record efficiency up to 22%.
Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have drawn considerable attention because of their remarkable optoelectronic properties of high emission efficiency and ...narrow emission profile, and represent an active subject of cutting‐edge research in the organic electroluminescence (EL). However, the slow reverse intersystem crossing (RISC) rate of MR‐TADF emitter caused by the large energy gap (ΔEST) and small spin‐orbit coupling (SOC) matrix elements between the singlet and triplet excited states limits their further development in organic EL devices. Currently, innovative molecular design strategies have been developed including heavy atom integration, π‐extended MR framework and metal perturbation, and so on to improve the RISC process of MR‐TADF emitters for high‐performance EL devices. Here, an overview is presented on the recent progress of MR‐TADF emitters with fast RISC rate ( > 10−5 s−1), with particular attention to the molecular design, optoelectronic properties, and device performance of organic light‐emitting diodes (OLEDs), which intends to systematize the knowledge in this subject for the thriving development of highly efficient MR‐TADF emitters. Finally, the challenges and future prospects of MR‐TADF materials are discussed comprehensively.
To guide the pathway toward the flourishing development of high‐performance organic electroluminescence devices, the recent progress of multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials is summarized with fast RISC rate constant (> 105 s−1) from the perspective of molecular design, optoelectronic properties, and device performance of organic light‐emitting diodes. Furthermore, the challenges and future prospects of MR‐TADF materials are discussed comprehensively.
•A survey of metal Schiff base complexes for energy-related applications is provided.•The potential of using these complexes as energy materials is highlighted and discussed.•The uses of metal Schiff ...base complexes in OLEDs and DSSCs are described.
Metal Schiff base complexes represent a class of compounds that have become a field of immense interest because of their intriguing chemical and physical properties, and their wide-ranging applications in a number of scientific areas. The presence of transition metal elements with a polydentate Schiff base ligand to form metal complexes offers a good platform for combining the chemical, electronic, magnetic, optical and redox properties of metal complexes with those of the organic materials. Metal Schiff base complexes can be incorporated into discrete small molecules, oligomers or polymers, generating new functional materials with useful mechanical, catalytic, thermal, chemical and optoelectronic properties. This review presents the contemporary research development of the field, with emphasis on the fundamental concepts, facile tuning of the photophysical properties and possible energy-related applications of various functional metal Schiff base complexes. To date, many soluble conjugated materials based on metal Schiff base complexes have been generated and studied. They have found an array of energy applications, for example, as converters for light/electricity signals in organic light-emitting diodes and dye-sensitized solar cells, energy storage and potential conductive thermoelectric materials.
Triple‐cation mixed perovskites have attracted much attention recently owing to their prominent optoelectronic properties and good stability for perovskite solar cells. However, the introduction of ...those cations with different sizes in the perovskite materials will drive the perovskite lattice away from ideal cubic structure and lead to microstrain in the resultant films. Herein,a small amount of KBF4 as an additive to elevate the quality of triple‐cation mixed perovskite thin films is introduced. It is found that KBF4 can enhance the crystallinity and alleviate microstrain of the perovskite thin films. Moreover, KBF4 can passivate defects in perovskite grains, leading to much longer carrier lifetimes. Consequently, the resultant devices show improved fill factor, enhanced device efficiency, and better device stability. Under optimum fabrication conditions, triple‐cation mixed perovskite solar cells with an inverted structure show power conversion efficiency over 23% as well as excellent stability under different conditions.
High‐performance inverted perovskite solar cells are fabricated with KBF4 additive in perovskite layers. The introduction of KBF4 can enlarge grain size, manipulate microstrain, and suppress the formation of deep trap states in the perovskite layers. The synergistic effects greatly elongate carrier lifetime and enable power conversion efficiencies over 23% and 21% for rigid and flexible devices.
Room‐temperature afterglow (RTA) materials with long lifetime have shown tremendous application prospects in many fields. However, there is no general design strategy to construct near‐infrared ...(NIR)‐excited multicolor RTA materials. Herein, we report a universal approach based on the efficient radiative energy transfer that supports the reabsorption from upconversion materials (UMs) to carbon dots‐based RTA materials (CDAMs). Thus, the afterglow emission (blue, cyan, green, and orange) of various CDAMs can be activated by UMs under the NIR continuous‐wave laser excitation. The efficient radiative energy transfer ensured the persistent multicolor afterglow up to 7 s, 6 s, 5 s, and 0.5 s by naked eyes, respectively. Given the unusual afterglow properties, we demonstrated preliminary applications in fingerprint recognition and information security. This work provides a new avenue for the activation of NIR‐excited afterglow in CDAMs and will greatly expand the applications of RTA materials.
A universal method is developed to activate near‐infrared‐excited multicolor afterglow of carbon dots‐based RTA materials (CDAMs) through radiative energy transfer from NaYF4:Yb,Tm upconversion materials (UMs). The resulting UM/CDAMs demonstrate bright and persistent afterglow from blue to orange under NIR CW laser excitation at 980 nm.
White polymer light‐emitting devices (WPLEDs) have become a field of immense interest in both scientific and industrial communities. They have unique advantages such as low cost, light weight, ease ...of device fabrication, and large area manufacturing. Applications of WPLEDs for solid‐state lighting are of special interest because about 20% of the generated electricity on the earth is consumed by lighting. To date, incandescent light bulbs (with a typical power efficiency of 12–17 lm W−1) and fluorescent lamps (about 40–70 lm W−1) are the most widely used lighting sources. However, incandescent light bulbs convert 90% of their consumed power into heat while fluorescent lamps contain a small but significant amount of toxic mercury in the tube, which complicates an environmentally friendly disposal. Remarkably, the device performances of WPLEDs have recently been demonstrated to be as efficient as those of fluorescent lamps.Here, we summarize the recent advances in WPLEDs with special attention paid to the design of novel luminescent dopants and device structures. Such advancements minimize the gap (for both efficiency and stability) from other lighting sources such as fluorescent lamps, light‐emitting diodes based on inorganic semiconductors, and vacuum‐deposited small‐molecular devices, thus rendering WPLEDs equally competitive as these counterparts currently in use for illumination purposes.
Recent advances in white polymer light‐emitting devices (WPLEDs) are summarized in terms of efficiency, stability and color quality, with special attention paid to the design of novel luminescent dopants and the device structure. Such advancements render WPLEDs as competitive as other lighting sources that are currently in use for illumination purposes.
Two‐dimensional (2D) nanomaterials are attracting much attention due to their excellent electronic and optical properties. Here, we report the first experimental preparation of two free‐standing ...mercurated graphyne nanosheets via the interface‐assisted bottom‐up method, which integrates both the advantages of metal center and graphyne. The continuous large‐area nanosheets derived from the chemical growth show the layered molecular structural arrangement, controllable thickness and enhanced π‐conjugation, which result in their stable and outstanding broadband nonlinear saturable absorption (SA) properties (at both 532 and 1064 nm). The passively Q‐switched (PQS) performances of these two nanosheets as the saturable absorbers are comparable to or higher than those of the state‐of‐the‐art 2D nanomaterials (such as graphene, black phosphorus, MoS2, γ‐graphyne, etc.). Our results illustrate that the two metallated graphynes could act not only as a new class of 2D carbon‐rich materials, but also as inexpensive and easily available optoelectronic materials for device fabrication.
Bottom‐up 2D metallated graphyne nanosheets exhibit their outstanding broadband nonlinear saturable absorption properties and can be used as excellent saturable absorbers in the passively Q‐switched Nd:YAG laser.
Excitation wavelength dependent (Ex‐De) emission materials have potential applications in anti‐counterfeiting labels and bioimaging. Nevertheless, few purely organic chromophores are used in these ...areas. In this study, multiple excited states were incorporated into a molecule that was excited state intramolecular proton transfer (ESIPT) active, with the goal of manipulating the relaxation pathways of the excited states. The triazole derivative exhibits Ex‐De photoluminescence (PL), and the maximum PL wavelength is located at 526 nm and 593 nm under a series of excitation wavelengths. Spectral identification indicates that the excimer and ESIPT processes are responsible for the green (526 nm) and orange (593 nm) fluorescence, respectively. Importantly, the quick response code and test strip prepared with this triazole derivative can be used for anti‐counterfeiting and food spoilage detection applications, respectively. This research opens the door for developing novel Ex‐De materials for anti‐counterfeiting purposes.
Molecular sleuth: Excitation wavelength dependent fluorescence behavior was achieved in an excited state intramolecular proton transfer (ESIPT) active chromophore by manipulating the relaxation pathways of the excited states. Moreover, the optical applications of this material, including in amine sensing and anti‐counterfeiting, have been demonstrated.
