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To absorb the photons below the band-gap energy effectively, we proposed a quantum dot (QD) photocell modeled by multi-level system for the quantum yields and photo-to-charge efficiency limits. The theoretical results show the quantum yields are enhanced as compared to the single band-gap solar cell, and the photo-to-charge efficiencies are larger than Shockley and Queisser efficiency in the same absorbed spectrum. What is more, at the room temperature the efficiency limits are well beyond 63% achieved by Luque and Marti (1997 Phys. Rev. Lett. 78 5014) due to absorbing the low-energy photons via two sub-bands in this proposed photocell system. The achievements may reveal a novel theoretical approach to enhance the QD photocell performance modeled a multi-level absorbing photons system.

The chemical structure of donors and acceptors limit the power conversion efficiencies achievable with active layers of binary donor-acceptor mixtures. Here, using quaternary blends, double cascading energy level alignment in bulk heterojunction organic photovoltaic active layers are realized, enabling efficient carrier splitting and transport. Numerous avenues to optimize light absorption, carrier transport, and charge-transfer state energy levels are opened by the chemical constitution of the components. Record-breaking PCEs of 18.07% are achieved where, by electronic structure and morphology optimization, simultaneous improvements of the open-circuit voltage, short-circuit current and fill factor occur. The donor and acceptor chemical structures afford control over electronic structure and charge-transfer state energy levels, enabling manipulation of hole-transfer rates, carrier transport, and non-radiative recombination losses. Efficiency of organic solar cells is determined by the physical properties of donors and acceptors in bulk heterojunction film. The authors optimise quaternary blends to realize a double cascading energy level alignment enabling efficient carrier dissociation and transport, achieving 18% efficiency.

Although much effort has been devoted to improving photoelectrochemical water splitting of hematite (α-Fe 2 O 3 ) due to its high theoretical solar-to-hydrogen conversion efficiency of 15.5%, the low applied bias photon-to-current efficiency remains a huge challenge for practical applications. Herein, we introduce single platinum atom sites coordination with oxygen atom (Pt-O/Pt-O-Fe) sites into single crystalline α-Fe 2 O 3 nanoflakes photoanodes (SAs Pt:Fe 2 O 3 -Ov). The single-atom Pt doping of α-Fe 2 O 3 can induce few electron trapping sites, enhance carrier separation capability, and boost charge transfer lifetime in the bulk structure as well as improve charge carrier injection efficiency at the semiconductor/electrolyte interface. Further introduction of surface oxygen vacancies can suppress charge carrier recombination and promote surface reaction kinetics, especially at low potential. Accordingly, the optimum SAs Pt:Fe 2 O 3 -Ov photoanode exhibits the photoelectrochemical performance of 3.65 and 5.30 mA cm −2 at 1.23 and 1.5 V RHE , respectively, with an applied bias photon-to-current efficiency of 0.68% for the hematite-based photoanodes. This study opens an avenue for designing highly efficient atomic-level engineering on single crystalline semiconductors for feasible photoelectrochemical applications. The achievable photocurrent of hematite, α-Fe 2 O 3 , is typically limited far below its theoretical limit. Here, the authors engineer single Pt atomic sites with surface oxygen vacancies into hematite photoanodes, which leads to enhanced photoelectrochemical water splitting.

Covalent organic frameworks (COFs) represent an emerging class of organic photocatalysts. However, their complicated structures lead to indeterminacy about photocatalytic active sites and reaction mechanisms. Herein, we use reticular chemistry to construct a family of isoreticular crystalline hydrazide-based COF photocatalysts, with the optoelectronic properties and local pore characteristics of the COFs modulated using different linkers. The excited state electronic distribution and transport pathways in the COFs are probed using a host of experimental methods and theoretical calculations at a molecular level. One of our developed COFs (denoted as COF-4) exhibits a remarkable excited state electron utilization efficiency and charge transfer properties, achieving a record-high photocatalytic uranium extraction performance of ~6.84 mg/g/day in natural seawater among all techniques reported so far. This study brings a new understanding about the operation of COF-based photocatalysts, guiding the design of improved COF photocatalysts for many applications. Covalent organic frameworks (COFs) represent an emerging class of organic photocatalysts but it remains challenging to gain insight into photocatalytic active sites and reaction mechanisms. Herein, the authors construct a family of isoreticular crystalline hydrazide-based COF photocatalysts, with the optoelectronic properties and local pore characteristics of the COFs modulated using different linkers

Energy management strategy is the essential approach for achieving high energy utilization efficiency of triboelectric nanogenerators (TENGs) due to their ultra-high intrinsic impedance. However, the proven management efficiency in practical applications remains low, and the output regulation functionality is still lacking. Herein, we propose a detailed energy transfer and extraction mechanism addressing voltage and charge losses caused by the crucial switches in energy management circuits. The energy conversion efficiency is increased by 8.5 times through synergistical optimization of TENG and switch configurations. Furthermore, a TENG-based power supply with energy storage and regularization functions is realized through system circuit design, demonstrating the stable powering electronic devices under irregular mechanical stimuli. A rotating TENG that only works for 21 s can make a hygrothermograph work stably for 417 s. Even under hand driving, various types of TENGs can consistently provide stable power to electronic devices such as calculators and mini-game consoles. This work provides an in-depth energy transfer and conversion mechanism between TENGs and energy management circuits, and also addresses the technical challenge in converting unstable mechanical energy into stable and usable electricity in the TENG field. Effective energy management is essential to enable triboelectric nanogenerators for realistic applications. Here, the authors optimize TENG and switch configurations to improve energy conversion efficiency and design a TENG-based power supply with energy storage and output regulation functionalities.

Recoilless launch can improve the adaptability of unmanned platforms to weapons by eliminating recoil, but it has the disadvantage of reducing the initial velocity of the projectile. The initial velocity of the recoilless gun can be improved by increasing the charge mass, so research into the recoilless efficiency of recoilless firing with increasing charge mass is of great importance for future applications of recoilless weapons. Based on the combustible cartridge and induction ignition, the one-dimensional homogeneous flow internal ballistic of a recoilless gun with high initial velocity is established. The effect of the Laval nozzle diameter on the efficiency of the recoilless gun is then investigated. The results show that, compared to conventional guns, the recoil can be reduced to 1N-s without reducing the initial velocity of the projectile. A ballistic test on a slide-rail mount is carried out to verify the results of the analysis. The results should make an important contribution to the development of a recoilless rifle.

The bulk semi-insulating GaAs material was used for preparation of pad radiation detectors with circular contacts of 1 mm diameter. The spectrometric properties of a semiconductor detector depend on the quality of the base material and on the deposited metallization. Another factor affecting the detector spectrometry is the applied bias controlling the electric collection field. With increasing bias, the charge collection efficiency of particular detector grows. However, this spectrometric property should be changing with detector thickness, which affects the intensity of electric collection field at constant bias applied through the detector sandwich structure. In this paper we have studied the electrical and spectrometric properties of semi-insulating GaAs detectors as a function of their thickness. The measured saturation reverse current was in the range of 3 – 30 nA, increasing with decreasing detector thickness at a substrate resistivity of about of 10 7 Ωcm. The maximal obtainable charge collection efficiency evaluated from 241 Am gamma spectra grew with decreasing detector thickness from 50% for a 450 µm thick detector to 80% for a 230 µm thick detector.

Bismuth Vanadate (BiVO4) is a promising photoanode material due to its stability and suitable bandgap, making it effective for visible light absorption. However, its photoelectrocatalytic efficiency is often limited by the poor transport dynamics of photogenerated carriers. Recent research found that varying the atomic arrangement in crystals and Fermi levels across different crystal orientations can lead to significant differences in carrier mobility, charge recombination rates, and overall performance. In this work, we optimized the atomic arrangement by controlling the crystal growth direction to improve carrier separation efficiency using a wet chemical method. Systematic investigations revealed that the preferential [010]-oriented BiVO4 film exhibits the highest carrier mobility and photocurrent density. Under an applied bias of 1.21 V (vs. RHE) in a 0.5 M Na2SO4 electrolyte, it achieved a photocurrent density of 0.2 mA cm−2 under AM 1.5 G illumination, significantly higher than that of the [121]-oriented (0.056 mA cm−2) and randomly oriented films (0.11 mA cm−2). This study provides a deeper understanding of the role of crystal orientation in enhancing photoelectrocatalytic efficiency.

Surface passivation has been developed as an effective strategy to reduce trap-state density and suppress non-radiation recombination process in perovskite solar cells. However, passivation agents usually own poor conductivity and hold negative impact on the charge carrier transport in device. Here, we report a binary and synergistical post-treatment method by blending 4- tert -butyl-benzylammonium iodide with phenylpropylammonium iodide and spin-coating on perovskite surface to form passivation layer. The binary and synergistical post-treated films show enhanced crystallinity and improved molecular packing as well as better energy band alignment, benefiting for the hole extraction and transfer. Moreover, the surface defects are further passivated compared with unary passivation. Based on the strategy, a record-certified quasi-steady power conversion efficiency of 26.0% perovskite solar cells is achieved. The devices could maintain 81% of initial efficiency after 450 h maximum power point tracking. The poor conductivity of passivators often impacts the charge carrier transport in perovskite solar cells. Here, the authors report a binary and synergistical post-treatment method to form the passivation layer, achieving certified quasi-steady power conversion efficiency of 26% for stable devices.

The growing importance of applications based on machine learning is driving the need to develop dedicated, energy-efficient electronic hardware. Compared with von Neumann architectures, which have separate processing and storage units, brain-inspired in-memory computing uses the same basic device structure for logic operations and data storage 1 – 3 , thus promising to reduce the energy cost of data-centred computing substantially 4 . Although there is ample research focused on exploring new device architectures, the engineering of material platforms suitable for such device designs remains a challenge. Two-dimensional materials 5 , 6 such as semiconducting molybdenum disulphide, MoS 2 , could be promising candidates for such platforms thanks to their exceptional electrical and mechanical properties 7 – 9 . Here we report our exploration of large-area MoS 2 as an active channel material for developing logic-in-memory devices and circuits based on floating-gate field-effect transistors (FGFETs). The conductance of our FGFETs can be precisely and continuously tuned, allowing us to use them as building blocks for reconfigurable logic circuits in which logic operations can be directly performed using the memory elements. After demonstrating a programmable NOR gate, we show that this design can be simply extended to implement more complex programmable logic and a functionally complete set of operations. Our findings highlight the potential of atomically thin semiconductors for the development of next-generation low-power electronics. Logic operations and reconfigurable circuits are demonstrated that can be directly implemented using memory elements based on floating-gate field-effect transistors with monolayer MoS 2 as the active channel material.