Search

Lanthanide ions doped in perovskite (LIDP) nanocrystals (NCs) provide an effective way to utilize the emission of lanthanide metals in a solution‐processable way, combining the theoretical photoluminance quantum yield (PLQY) of ≈200%. To utilize advantages, LIDP‐NCs have inspired studies exploring the fundamental physics of energy transfer, including the up‐conversion or down‐conversion process, and the optoelectronic applications of solar cells and white light‐emitting didoes. This review broadens the scope of LIDP nanocrystal matrix semiconductors in electroluminescence devices in the near‐infrared (NIR) range (>900 nm). A research is summarized on the synergistic effect of lanthanide ions and perovskite matrix in the near‐infrared region, and discuss from the perspective of fabrication of lanthanide‐based electroluminescent devices using perovskite materials as the matrix. The multiple optical transitions, bandgap tunability, and quantum‐cutting effect to provide a tutorial on understanding LIDP‐NCs are started. The details of synthesizing LIDP materials and aim to lay the foundation for preparing NIR electroluminescent devices with high efficiency and application value are then illustrated. The scientific issues that limit the performance of LIDP NCs‐based electroluminescent devices and discuss the potential strategies for the future development of LIDP material are focused on. [ABSTRACT FROM AUTHOR]

Lanthanide ions (Yb3+ or Er3+) alloying of CsPb(Cl1‐xBrx)3 quantum dots (QDs) to emit approaching 1000 nm show promise in near‐infrared light‐emitting diodes (NIR‐LEDs). High Yb3+ alloying ratio increases the electroluminance efficiency of emission at 990 nm and enables high external quantum efficiency (EQE) of NIR‐LEDs, however, the high alloying ratio also results in inferior material stability and PLQY drop because of Yb3+‐induced nanocrystal precipitation. This study finds that the heavy alloying of Yb3+ ions causes lattice distortion and coherent energy reduction of Yb3+: CsPb(Cl1‐xBrx)3 QDs, induced by two Yb3+ ions replacing three Pb2+, which leads to the collapse of the octahedral structure in ambient conditions. It posits that spontaneous monovalent ion (Na+) alloying can address the trade‐off between material stability and emission intensity. The Na+ occupies the vacancy of Pb2+ ions, relaxing the distortion in the lattice and improving the phase stability of octahedral structure, and this optimized structure in turn allows a higher Yb3+ alloying ratio. Stability measurements show that the Na+/Yb3+ co‐alloyed films show ten‐fold higher material stability and 2.0‐fold emission efficiency related to controls. It reports that as a result Na+/Yb3+ co‐alloyed NIR‐LEDs have an EQE of 6.4% at 990 nm, which is among the highest perovskite NIR‐LEDs beyond 950 nm. [ABSTRACT FROM AUTHOR]

Films with excellent flexibility and mechanical stability are important for flexible and wearable devices. However, most films reported are prepared on substrates, and the synthesis of freestanding flexible films remains a challenge. Herein, a freestanding Bi2S3 nanofibrous membrane (NFM) is successfully prepared via a one‐step hydrothermal method, which is self‐assembled from ultralong Bi2S3 nanowires (NWs) over a length of millimeter‐scale crisscrossing each other. Significantly, the Bi2S3 NFM can be bent or clipped into an arbitrarily desired form. Based on the freestanding Bi2S3 NFM, an IR photodetector is fabricated, depicting a robust responsivity of 2.23 (2.06) µA W−1 under 850 (940) nm illumination. The Bi2S3 NFM photodetector exhibits a relatively fast response time (47.1 ms), which is attributed to high‐speed carrier transport efficiency in the NWs network. Under the bending states, the device still exhibits excellent detection performance, maintaining more than 86% of the initial photocurrent even after 1000 bending‐flattening times. The robust photoresponse of the Bi2S3 NFM photodetector after 2 months of storage in air and after 1 week in the bending state illustrates its excellent air stability and flexible detection ability. Besides, the photodetector can clearly identify the target image, indicating widespread potential applications in flexible and wearable fields. [ABSTRACT FROM AUTHOR]

The substrates of conventional flexible perovskite solar cells (FPSCs) are thermoplastic polymer material polyethylene naphthalate (PEN), which will deform during high temperature annealing process. In addition, lead iodide (PbI2) permanently formed and the substrate undergoes reversible deformation from 20 °C to 200 °C and back to 20 °C. Therefore, to balance the substrate supporting capacity and the crystalline quality of narrow band gap α‐phase formamidinium lead iodide (α‐FAPbI3), an annealing process of 120 °C for 30 minutes is determined. Additionally, there will also be a large number of gaps and lattice strain at the perovskite grain boundaries during the annealing process as the FAPbI3 phase transition is accompanied by much lattice shrinkage. As a result, 1,6‐hexanediammonium diiodide (HADI) is chosen to passivate the defects and release the stress of perovskite film. Therefore, a recorded 1.4% extended stretch rate of the flexible film is attained. Finally, the champion PCE of 21.14% under AM 1.5G and 31.52% under 1062 lux is achieved after HADI treatment, accompanied by a better long‐term and mechanical stability. This study provides annealing process optimization and stress relief strategies for the further development of narrow band gap FPSCs. [ABSTRACT FROM AUTHOR]

As a recently emerging group of 2D materials, MXene has attracted extensive attention in the energy storage field in recent years owing to their outstanding features. However, the notorious issues of inevitable oxidation stability and surface‐to‐surface self‐restacking for MXene significantly prevent its further wide‐ranging application. Herein, the 3D macroporous oxidation‐resistant Ti3C2Tx MXene/graphene/carbon nanotube (MRC) hybrid hydrogels are prepared by a simple gelation method assisted by l‐cysteine as crosslinker and l‐ascorbic acid (VC) as reductant. Benefitting from the effectively alleviated restacking, excellent electrical conductivity, and the 3D inter‐crosslinked macroporous architecture, as a supercapacitor electrode, the obtained MRC aerogel exhibits a superior specific capacitance of 349 F g−1, unparalleled rate capability (52.0% at 3000 mV s−1) and amazing cyclic stability (retention of 97.1% after 100 000 cycles). Moreover, the 3D MRC‐30 aerogel exhibits an impressive oxidation‐resistant performance with just a 9.3% increase in electrical resistance after storing in ambient condition for 60 days, effectively alleviating the oxidation problem of MXene. This work demonstrates a new method for construction of 3D oxidation‐resistant MXene hydrogel, shedding new light on the promising applications of MXene materials, especially in high humidity and oxygen environment. [ABSTRACT FROM AUTHOR]

Type 2 diabetes, lowly responsive to insulin injection, is a difficult chronic disease which requires therapeutic breakthroughs. Herein, a new concept is proposed to remotely control the glucose metabolism by a near‐infrared (NIR) laser for the treatment of type 2 diabetes for the first time. This method integrates fluorescent upconversion nanoparticles with the optogenetic technique to selectively activate the phosphoinositide 3‐kinase/AKT signaling pathways, in an insulin‐independent manner for type 2 diabetic treatments. It features fast responsiveness (in seconds) to NIR, deep tissue penetration (up to centimeters), and tunable dosage by adjusting laser irradiation. Successful glucose metabolic regulation has been demonstrated both in vitro and in vivo, thus offering the possibility of developing new alternative strategies to meet the clinical challenges in the treatment of type 2 diabetes. [ABSTRACT FROM AUTHOR]

Potassium‐ion hybrid capacitors have attracted increasing attention due to good energy density, high power density, and low cost. Ti3C2Tx‐MXene is considered as a promising anode material for K ion storage. However, undesirable stacking issues decrease its exposed area and breeds sluggish K ion transport. Herein, a facile spray‐lyophilization strategy is proposed to construct stacking‐resistant Ti3C2Tx with 3D structures. As‐prepared Ti3C2Tx hollow spheres/tubes present stack resistance, a large specific surface area, and a short ion diffusion pathway. When serving as an anode material, it shows enhanced capacity and thickness‐independent rate performance compared to 2D Ti3C2Tx. After 10 000 cycles, a specific capacity of 122 mAh g−1 is obtained at 1 A g−1. Systematic kinetics analyses demonstrate the significance of concentration polarization on the electrode's rate ability. Furthermore, a 3D Ti3C2Tx‖hierarchical porous activated carbon (HPAC) K‐ion hybrid capacitor is assembled and displays remarkable energy and power densities with energy retention of 100% after 10 000 cycles at 1 A g−1. Following this strategy, other 3D structures from nanosheets can also be obtained, such as 3D Ti3C2Tx microtubes and graphene oxide nanoscrolls. This study provides a viable approach to solve the stacking issues of 2D nanosheets to promote the application of 2D materials. [ABSTRACT FROM AUTHOR]

Hematite (α‐Fe2O3) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The construction of p–n junction nanostructures by coupling of highly stable Co3O4 in aqueous alkaline environment to Fe2O3 nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p‐Co3O4/n‐Fe2O3 junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (ηinj and ηsep), attributing to the high catalytic behavior of Co3O4 for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co‐Pi) is introduced, which brings the PEC performance to a high level. The resultant Co‐Pi/Co3O4/Ti:Fe2O3 photoanode shows a photocurrent density of 2.7 mA cm−2 at 1.23 VRHE (V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe2O3 photoanode. The optimized ηinj and ηsep of 91.6 and 23.0% at 1.23 VRHE are achieved on Co‐Pi/Co3O4/Ti:Fe2O3, respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe2O3. Furthermore, Co‐Pi/Co3O4/Ti:Fe2O3 shows a low onset potential of 0.64 VRHE and long‐time PEC stability. A well‐designed Co‐Pi/Co3O4/Ti:Fe2O3 photoanode displays efficient charge separation and transportation efficiency due to the induced interfacial electric field in the Co3O4/Ti:Fe2O3 p–n junction, as well as the fast water oxidation kinetics deriving from the high catalytic behavior of Co3O4 and Co‐Pi. [ABSTRACT FROM AUTHOR]