Metal-organic framework-derived NiCo 2.5 S 4 microrods wrapped in reduced graphene oxide (NCS@RGO) were synthesized for potassium-ion storage.Upon coordination with organic potassium salts,N CS@RGO exhibits an ultrahigh initial reversible specific capacity (602 mAh g À1 at 50 mA g À1 ) and ultralong cycle life (a reversible specific capacity of 495 mAh g À1 at 200 mA g À1 after 1900 cycles over 314 days). Furthermore,t he battery demonstrates ah igh initial Coulombic efficiency of 78 %, outperforming most sulfides reported previously.A dvanced ex situ characterization techniques,i ncluding atomic force microscopy, were used for evaluation and the results indicate that the organic potassium salt-containing electrolyte helps to form thin and robust solid electrolyte interphase layers,w hichr educe the formation of byproducts during the potassiation-depotassiation process and enhance the mechanical stability of electrodes.T he excellent conductivity of the RGO in the composites,a nd the robust interface between the electrodes and electrolytes,i mbue the electrode with useful properties;i ncluding,u ltrafast potassium-ion storage with areversible specific capacity of 402 mAh g À1 even at 2Ag À1 .

The vertical composition distribution of a bulk heterojunction (BHJ) photoactive layer is known to have dramatic effects on photovoltaic performance in polymer solar cells. However, the vertical composition distribution evolution rules of BHJ films are still elusive. In this contribution, three BHJ film systems, composed of polymer donor PBDB-T, and three different classes of acceptor (fullerene acceptor PCBM, small-molecule acceptor ITIC, and polymer acceptor N2200) are systematically investigated using neutron reflectometry to examine how donor–acceptor interaction and solvent additive impact the vertical composition distribution. Our results show that those three BHJ films possess homogeneous vertical composition distributions across the bulk of the film, while very different composition accumulations near the top and bottom surface were observed, which could be attributed to different repulsion, miscibility, and phase separation between the donor and acceptor components as approved by the measurement of the donor–acceptor Flory–Huggins interaction parameter χ. Moreover, the solvent additive 1,8-diiodooctane (DIO) can induce more distinct vertical composition distribution especially in nonfullerene acceptor-based BHJ films. Thus, higher power conversion efficiencies were achieved in inverted solar cells because of facilitated charge transport in the active layer, improved carrier collection at electrodes, and suppressed charge recombination in BHJ solar cells.

On account of the large radius of K-ions, the electrodes can suffer huge deformation during K-ion insertion and extraction processes. In our work, we unveil the impact of using carboxymethyl cellulose (CMC) instead of poly-(vinylidene fluoride) (PVDF) as binders for K-ion storage. Our porous hollow carbon submicrosphere anodes using the CMC binder exhibit a reversible capacity of 208 mA h g −1 after 50 cycles at 50 mA g −1 , and even at a high current density of 1 A g −1 , they achieve a reversible capacity of 111 mA h g −1 over 3000 cycles with almost no decay, demonstrating remarkably improved reversibility and cycling stability than those using PVDF (18 mA h g −1 after 3000 cycles at 1 A g −1 ). It is showed that the CMC binder can result in higher adhesion force and better mechanical performance than the PVDF binder, which can restrain the crack during a potassiation/depotassiation process. According to the test of adhesion force, the hollow carbon submicrospheres using the CMC binder show above three times of average adhesion force than that using the PVDF binder. Furthermore, based on the rational design, our hollow carbon submicrospheres also exhibit 62.3% specific capacity contribution below 0.5 V vs K/K + region, which is helpful to design the full cell with high energy density. We believe that our work will highlight the binder effect to improve the K-ion storage performance.

Two-dimensional (2D) hybrid perovskites have been extensively studied as the promising light-sensitive materials in the photodetectors owing to their improved structural stability over that of their three-dimensional counterparts. However, the application of the 2D perovskite-based photodetector in the near-infrared (NIR) region is obstructed by the large intrinsic optical band gap. Herein, we develop a novel van der Waals heterostructure composed of few-layer 2D perovskite/MoS2 nanoflakes, which exhibits high-sensitivity detection performance over a broad spectral region, from the visible region to the telecommunication wavelength (i.e., 1550 nm). In particular, the photoresponsivity and specific detectivity under an 860 nm laser reach 121 A W–1 and 4.3 × 1014 Jones, respectively, whereas the individual nanoflakes show no response under the same wavelength. Meanwhile, the response time at the microsecond (μs) level is obtained, shortened by around 3 orders of magnitude compared to that of the constituting layers. The sensitive and ultrafast photoresponse at the NIR wavelength stems from the strong interlayer transition of sub-band-gap photons and the rapid separation of the photogenerated carriers by the built-in field within the heterojunction area. Our results not only provide an effective approach to achieve sub-band-gap photodetection in 2D perovskite-based structures but also suggest a universal strategy to fabricate high-performance optoelectronic devices.

The vertical component distribution of bulk heterojunction (BHJ) active film shows a significant impact on determining the device performance in polymer solar cells (PSCs). Processing solvent additives are well known for regulating the BHJ active layer morphology; however, there are few reports regarding the quantitative evaluation of the effect. Herein, a study of the quantitative determination of the vertical segregation in combination of molecular ordering of PBDB-T/ITIC blend films with various 1,8-diiodooctane (DIO) contents is provided. A 0.5% (volume ratio) DIO-added blend film achieves the highest power conversion efficiency of 10.75%. The reduced performance of the PSCs resulted from the excessive vertical component segregation and overcrystallization investigated by various techniques. X-ray photoelectron spectroscopy indicates that DIO aggravates the PBDB-T enrichment region at the air side. Neutron reflectivity further quantitatively figures out the phase separation effect. Although increased crystallinity of ITIC and a higher face-on ratio of PBDB-T in active layer were obtained with increased DIO content approved by grazing-incidence wide-angle X-ray scattering (GIWAXS), the enhanced vertical distribution along with the enhanced crystal size of ITIC leads to the reduced performance of the PSCs due to the reduced carrier transportation paths between donor and acceptor.

In this study, Wadsley B phase vanadium oxide (VO 2 (B)) with broad-band photoabsorption ability, a large temperature coefficient of resistance (TCR), and low noise was developed for uncooled broad-band detection. By using a freestanding structure and reducing the size of active area, the VO 2 (B) photodetector shows stable and excellent performances in the visible to the terahertz region (405 nm to 0.88 mm), with a peak TCR of −4.77% K −1 at 40 °C, a peak specific detectivity of 6.02 × 10 9 Jones, and a photoresponse time of 83 ms. A terahertz imaging ability with 30 × 30 pixels was demonstrated. Scanning photocurrent imaging and real-time temperature−photocurrent measurements confirm that a photothermal-type bolometric effect is the dominating mechanism. The study shows the potential of VO 2 (B) in applications as a new type of uncooled broad-band photodetection material and the potential to further raise the performance of broad-band photodetectors by structural design.

Defects engineering can broaden the absorption band of wide band gap van der Waals (vdW) materials to the visible or near-IR regime at the expense of material stability and photoresponse speed. Herein, we introduce an atomic intercalation method that brings the wide band gap vdW α-MoO3 for vis–MIR broadband optoelectronic conversion. We confirm experimentally that intercalation significantly enhances photoabsorption and electrical conductivity buts effects negligible change to the lattice structure as compared with ion intercalation. Charge transfer from the Sn atom to the lattices induces an optoelectrical change. As a result, the Sn-intercalated α-MoO3 shows room temperature, air stable, broadband photodetection ability from 405 nm to 10 μm, with photoresponsivity better than 9.0 A W–1 in 405–1500 nm, ∼0.4 A W–1 at 3700 nm, and 0.16 A W–1 at 10 μm, response time of ∼0.1 s, and peak D* of 7.3 × 107 cm Hz0.5 W–1 at 520 nm. We further reveal that photothermal effect dominates in our detection range by real-time photothermal–electrical measurement, and the materials show a high temperature coefficient of resistance value of −1.658% K–1 at 300 K. These results provide feasible route for designing broadband absorption materials for photoelectrical, photothermal, or thermal–electrical application.

inevitable, which reduces the reliability in high-density integration. Furthermore, uncontrollable interface is detrimental to the retention time and operation speed of the memory device. 2D van der Waals (vdW) crystals manifest ultra-thin layered structure, highly anisotropic in-and outof-plane conductivity and superior carrier migration, [6] which are promising to solve the above problems. Over the past decade, 2D vdW atomic crystals, such as graphene, MoS 2 , ReS 2 , etc., are widely used as the composed elements in FGNVM, [7][8][9][10][11] and extended device structures are proposed to improve the performance. [12,13] It has been demonstrated that the FGNVM based on vdW heterostructure could enable atomically sharp interface for ultrafast operation at tens of nanosecond. [14][15][16] Nonetheless, the investigation is still in the initial stage and much research work has to be carried out before the commercialization of the vdW-heterostructure-based nonvolatile memory. In conventional FGNVM, the program/erase operations are accomplished by electrical stimuli. The repetitive voltage drives not only increase the power consumption, but also deteriorate the reliability and stability of the device. [17] Light, as an efficient non-contact signal, has a small energy dissipation when traveling through the free space. Therefore, using light illumination as an auxiliary programming method is beneficial to realize long-distance quantum communication, while effectively minimizing the power consumption, so as to improve the reliability The development of floating-gate nonvolatile memory (FGNVM) is limited by the charge storage, retention and transfer ability of the charge-trapping layer.Here, it is demonstrated that due to the unique alternate inorganic/organic chain structure and superior optical sensitivity, an insulating 2D Ruddlesden-Popper perovskite (2D-RPP) layer can function both as an excellent chargestorage layer and a photosensitive layer. Optoelectronic memory composed of a MoS 2 /hBN/2D-RPP (MBR) van der Waals heterostructure is demonstrated. The MBR device exhibits unique light-controlled charge-storage characteristics, with maximum memory window up to 92 V, high on/off ratio of 10 4 , negligible degeneration over 10 3 s, >1000 program/erase cycles, and write speed of 500 µs. Dependent on the initial states, the MBR optoelectronic memory can be programmed in both positive photoconductivity (PPC) and negative photoconductivity (NPC) modes, with up to 11 and 22 distinct resistance states, respectively. The optical program power for each bit is as low as 36/10 pJ for PPC/NPC. The results not only reveal the potential of 2D-RPP as a superior charge-storage medium in floating-gate memory, but also provides an effective strategy toward fast, low-power and stable optical multi-bit storage and neuromorphic computing.