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Temperature is known as an important factor in biological synaptic transmission. In this study, temperature-modulated switching behaviors are reported in an amorphous carbon (a-C) diffusive memristor device to emulate biorealistic synaptic plasticity. The devices exhibit memory switching and threshold switching behaviors depending on the compliance current and ambient temperature. As confirmed by conducting atomic force microscopy, the thermal effect can promote the electrochemical formation of a stable metallic conductive filament. A series of timing-controlled pulse experiments are carried out to study the temperature effect on the switching characteristics, and the device shows second-order memristive behaviors. Frequency-dependent synaptic plasticity and timing-controlled spike-time-dependent plasticity are demonstrated in the device, which are analogous to the synaptic strength in a biological synapse at elevated temperatures. As a proof of concept, the forgetting behavior of numerical images learned at different temperatures and different pulse durations is conceptually emulated with synaptic device arrays. It is expected the present device with second order memristive behaviors provides alternatives for biorealistic synaptic applications.

Interface engineering, which efficiently optimizes the interfacial carrier collection and recombination, has been proven to be of importance for the emerging colloidal quantum dot solar cells (CQDSCs). Compared with the attractive modification efforts at the interface between quantum dots and the anode/electron transport layer (ETL), the interface between fluorine-doped tin-oxide (FTO) cathodes and the ETL, for which there exists a band alignment mismatch and high trap density in ZnO, has been investigated less. Herein, two kinds of ethylenimine-based polymers, branched by only ethylenimine groups (b-PEI) and by both ethylenimine/ethoxylated groups (e-PEI), respectively, are introduced as bifunctional interfacial layers (BILs) in lead sulfide (PbS) CQDSCs. PEI-based BILs were utilized to modulate the work function of an FTO cathode for optimizing the band alignment at the FTO/ZnO interface and to control the crystallinity of ZnO for reducing its traps. These BILs suppressed the interfacial carrier recombination and achieved a power conversion efficiency (PCE) of 11.28% in CQDSCs, which was much superior to the PCE of the reference device without BIL (10.29%). Also, the branched side chain of PEI-based BILs plays a crucial role in rationally modulating the Schottky barrier to gain different interface-optimization effects. Our work has laid a foundation for the commercial application of CQDSCs due to the advantage of low-temperature solution processability, low-cost, and scalable manufacturing.

Flexible and floating photocatalysts have unique advantages in water pollution treatment due to their light-harvesting and recycle performance. Here, a facile successive ionic layer adsorption and reaction (SILAR) method was used to layer by layer grow BiOCl/BiOI heterojunctions on self-supporting electrospun polyacrylonitrile (PAN) nanofiber mats at room temperature. This method enables tunable good interface contact of the heterojunctions while makes the composites maintain flexibility and floatable properties. The PAN/BiOCl/BiOI nanofibers show much better photocatalytic activity than the PAN/BiOCl and PAN/BiOI nanofibers. For removal of Rhodamine-B and Bisphenol-A, the degradation rates of PAN/BiOCl/BiOI nanofibers were about 1.68 and 1.41 times higher than PAN/BiOCl nanofibers and were 2.27 and 2.01 times higher than PAN/BiOI nanofibers, respectively. The high photocatalytic performance could be attributed to the effective interfacial charge separation of BiOCl/BiOI heterojunctions, confirmed by the enhanced photocurrent densities, and significantly decreased photoluminescence intensity. The photocatalytic activity of these composite nanofibers could be further improved by adjusting the contents of BiOCl and BiOI in the heterojunction due to the excellent controllability of the SILAR method. Furthermore, the PAN/BiOCl/BiOI nanofibers can float easily and directly reused due to their flexible and self-supporting fiber mats structures. It was expected that the PAN/BiOCl/BiOI nanofibers with high photocatalytic activity and easily separable properties would be useful for industrial wastewater remediation.

Colloidal quantum dot solar cells (CQDSCs) are good candidates for low-cost power generators, due to their wide light-response range, high theoretical efficiency, and solution processability. Never...

PbS colloidal quantum dot solar cells (CQDSCs) employ ZnO electron transport layer have achieved high efficiency. However, there is nearly no efficient and batch production method to balance the charge separation and recombination within the device, which is one of the most obviously barrier to a satisfactory conversion efficiency. Here, a n+-n double-layered ZnO electron transport layer (DETL) is prepared by a facile one-step magnetron sputtering under different Ar pressure, and employed in heterojunction PbS colloidal quantum dot solar cells (CQDSCs) for the purpose of increasing charge separation at heterojunction interface via energy-band alignment modulation. The ZnO DETL, composed of a 100-nm-thick n+-ZnO bottom layer (n = 8 × 1019 cm−3) and a 20-nm-thick n-ZnO top layer (n = 3 × 1016 cm−3) significantly improve the power conversion efficiency (PCE) of the CQDSCs by a factor of ~35% compared to the device with single-layered n- ZnO. Open-circuit photovoltage decay (OCVD) measurements prove that the graded energy alignment of ZnO DETL effectively reduces both interfacial and trapping-assisted charge recombination, relative to the single-layered ZnO. The facile Ar-pressure tuning method makes the energy-band alignment process more convenient and sheds a light on the application of DETL electrons transport layer, fabricated by the universal technique of magnetron sputtering.

Z-scheme narrow bandgap heterojunctions can efficiently absorb solar light and provide high reduction and oxidation ability for photocatalysis. However, it is difficult to tune the Z-scheme interface charge transfer to achieve high charge separation. Here, we introduced a Schottky contact surface to promote Z-scheme interface charge separation. Thin g-C3N4 nanolayers of 50–60 nm were evenly grown on NiTiO3 nanofibers forming a Z-scheme core@shell interface, and Au nanoparticles of ∼10 nm were dispersed in the g-C3N4 nanolayer developing an additional Schottky contact surface. The Z-scheme core@shell interface and dispersive Schottky contact surface could generate a uniform radial electric field, providing continuous charge transfer channels. Photocurrent and photoluminescence confirmed the improved charge separation in the NiTiO3@g-C3N4–Au nanofibers. The ternary photocatalysts had enhanced photocatalytic activities under simulated solar light. Their hydrogen evolution rate was 212.50 μmol g−1 h−1, which was 4.22, 2.81 and 4.85 times higher than that of binary NiTiO3@g-C3N4 nanofibers, g-C3N4–Au and g-C3N4. For water treatment, their first-order rate constant of Rhodamine B oxidation was 0.033 min−1, which was 3.73, 3.83, 4.95 and 21.5 times higher than that of binary NiTiO3@g-C3N4 nanofibers, g-C3N4–Au, g-C3N4, and NiTiO3 nanofibers. The ternary photocatalysts also had relatively stable activity at various pH values, good separability, and recyclability. This work presents new insight into designing ternary photocatalysts with a synergistic interface and surface for photocatalysis.

Memristive devices are widely recognized as promising hardware implementations of neuromorphic computing. Herein, a flexible and transparent memristive synapse based on polyvinylpyrrolidone (PVP)/N-doped carbon quantum dot (NCQD) nanocomposites through regulating the NCQD doping concentration is reported. In situ Kelvin probe force microscopy showed that the trapping/detrapping of space charge can account for the memristive mechanism of the device. Diverse synaptic functions, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), spike-timing-dependent plasticity (STDP), and the transition from short-term plasticity (STP) to long-term plasticity (LTP), are emulated, enabling the PVP–NCQD hybrid system to be a valuable candidate for the design of novel artificial neural architectures. In addition, the synaptic device showed excellent flexibility against mechanical strain after repeated bending tests. This work provides a new approach to develop flexible and transparent organic artificial synapses for future wearable neuromorphic computing systems.

Inefficient charge injection and transport across the electrode/semiconductor contact edge severely limits the device performance of coplanar organic thin-film transistors (OTFTs). To date, various approaches have been implemented to address the adverse contact problems of coplanar OTFTs. However, these approaches mainly focused on reducing the injection resistance and failed to effectively lower the access resistance. Here, we demonstrate a facile strategy by utilizing the blurring effect during the deposition of metal electrodes, to significantly reduce the access resistance. We find that the transition region formed by the blurring behavior can continuously tune the molecular packing and thin-film growth of organic semiconductors across the contact edge, as well as provide continuously distributed gap states for carrier tunnelling. Based on this versatile strategy, the fabricated dinaphtho[2,3

Colloidal quantum dots (CQDs) have a large specific surface area and a complex surface structure. Their properties in diverse optoelectronic applications are largely determined by their surface chemistry. Therefore, it is essential to investigate the surface chemistry of CQDs for improving device performance. Herein, we realized an efficient surface chemistry optimization of lead sulfide (PbS) CQDs for photovoltaics by annealing the CQD solution with concentrated lead halide ligands after the conventional solution-phase ligand exchange. During the annealing process, the colloidal solution was used to transfer heat and create a secondary reaction environment, promoting the desorption of electrically insulating oleate ligands as well as the trap-related surface groups (Pb-hydroxyl and oxidized Pb species). This was accompanied by the binding of more conductive lead halide ligands on the CQD surface, eventually achieving a more complete ligand exchange. Furthermore, this strategy also minimized CQD polydispersity and decreased aggregation caused by conventional solution-phase ligand exchange, thereby contributing to yielding CQD films with twofold enhanced carrier mobility and twofold reduced trap-state density compared with those of the control. Based on these merits, the fabricated PbS CQD solar cells showed high efficiency of 11% under ambient conditions. Our strategy opens a novel and effective avenue to obtain high-efficiency CQD solar cells with diverse band gaps, providing meaningful guidance for controlling ligand reactivity and realizing subtly purified CQDs.

Gas sensors based on polymer field-effect transistors (FETs) have drawn much attention owing to the inherent merits of specific selectivity, low cost, and room temperature operation. Ultrathin (

Semiconductor oxides are widely used to achieve photocatalytic removal of NOx (NO and NO2) species. These materials also exhibit enhanced oxidation ability in thermally assisted photocatalysis; however, many of them tend to be deactivated at high relative humidity (RH) levels. In the case of the benchmark P25 TiO2 photocatalyst, we observe a significant decrease in non-NO2 selectivity from 95.02% to 58.33% when RH increases from 20% to 80%. Interestingly, the porous TiO2(B) microspheres synthesized in this work exhibit 99% selectivity at 20% RH; the selectivity remains as high as 96.18% at 80% RH. The high humidity tolerance of the TiO2(B) sample can be ascribed to its strong water desorption capacity and easy O2 adsorption at elevated temperatures, which reflects the fact that the superoxide radical is the main active species for the deep oxidation of NOx. This work may inspire the design of efficient photothermal catalysts with application in NOx removal in hot and humid environments.

Lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) are emerging photovoltaic technology due to their outstanding light-harvesting ability in the visible and near-infrared spectral region, long-term air stability, multiple exciton generation and solution processability. However, PbS CQDSCs have been limited by the unsatisfactory carrier collection in the CQD films. Band alignment engineering using p-type hole transport layer (HTL) was proved to efficiently promote the carrier collection in cells with both planar and ordered bulky heterojunctional (OBH) structures. Nevertheless, seeking for proper p-type materials suitable for the PbS CQDSCs is still an open question. Herein, we reported a new p-type metal-organic material, CuSx, could act as HTL of PbS CQDSCs with OBH structure. The CuSx possesses a Fermi level EF (−5.02 eV), shallower valence band energy (−5.48 eV) and conduction band energy (−3.19 eV), inducing a proper band alignment at the PbS light-harvesting layer/CuSx interface. This not only enhanced hole extraction proved by the increase of short-circuit current density (Jsc) from 19.12 to 22.33 mA/cm2, but also blocked back electron demonstrated by the extended carrier lifetime. Consequently, cells with CuSx HTL generated a power conversion efficiency of 5.2%, leading to a PCE increase of 13% compared with that of reference HTL-free cell (4.6%). Our work introduced a promoting CuSx hole extraction material which shows great potential application in quantum-dot-based devices suffering from the insufficient carrier collection.

The perovskite structure BaSnO3 is regarded as a promising photoanode material, and an effective necking treatment strategy is necessary for the electrical connectivity of mesoporous BaSnO3 photoanode-based solar cells. The often-adopted necking strategy involves the treatment in TiCl4 solution with low pH, which can lead to the leaching of barium cations from BaSnO3 and impair the effect of the necking treatment. To address this issue, we report herein a novel noncorrosive necking strategy based on the common ion effect. The strategy involved treating the mesoporous BaSnO3 photoanode with a mixture solution of TiCl4 and BaCl2. Compared with the common TiCl4 necking treatment, the treatment with TiCl4 and BaCl2 mixture solution negligibly affected the formation of the TiO2 overlayer on the surface of BaSnO3 particles, but it maintained the crystallinity of the BaSnO3 particles. The TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanodes were assembled into CdSe/CdS co-sensitized quantum dot-sensitized solar cells (QDSSCs), which showed ca. 37% increase in power conversion efficiency in comparison with the TiCl4 treated photoanode. The charge extraction, electrochemical impedance spectroscopy, and intensity-modulated voltage/photocurrent spectroscopy measurements showed that the QDSSCs fabricated from the TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanode contained fewer trap states and exhibited less charge recombination and longer electron lifetime than those based on the common TiCl4 treated photoanodes, demonstrating the effectiveness of the noncorrosive necking treatment.

Electrospun cellulose nanofibers are promising biomaterials but are suffering from the use of unfavorable organic solvents during the electrospinning process. In this manuscript, we used the periodate oxidation—adipic acid dihydrazide crosslinking strategy to fabricate electrospun cellulose nanofibers. Periodate oxidation of cellulose generated water soluble aldehyde cellulose, which thus allowed for the electrospinning in aqueous solution and avoided the use of unfavorable organic solvents. The following crosslinking with adipic acid dihydrazide made the nanofibers water resistant. The results show that the prepared cellulose nanofiber mats show moderate wet mechanical strength around 1 MPa, are able to absorb water equal to 30 times of their own weight, can degrade gradually by hydrolysis, and are cytocompatible. These cellulose nanofibers are expected to find applications in biomedical fields such as wound healing and tissue regeneration.

Designing and constructing one-dimensional (1D) discrete heterojunctions comprise an ideal strategy to improve the charge-separation efficiency and enhance the photocatalytic activities of semiconductor materials. Here, a novel architecture of discrete heterojunction nanofibers (DH-NFs) was obtained by growing Bi2WO6 nanosheets (NSs) on electrospun BiFeO3 nanofibers (NFs) via solvothermal technology. The charge-separation efficiency of BiFeO3/Bi2WO6 DH-NFs was approximately 2 times higher than that of BiFeO3 NFs and Bi2WO6 NSs. As expected, the BiFeO3/Bi2WO6 DH-NFs exhibited enhanced photocatalytic activities for oxygen evolution and RhB degradation. The reaction rates of BiFeO3/Bi2WO6 DH-NFs for oxygen evolution and RhB degradation were 18.3 and 36.7 times higher, respectively, than those of BiFeO3 NFs, and 31.9 and 8.7 times higher than those of Bi2WO6 NSs, respectively. The improved charge-separation efficiency and enhanced photocatalytic activities of BiFeO3/Bi2WO6 DH-NFs could be attributed to the following three points. The 1D heterojunctions could realize the separation and axial transport of photogenerated charges. The discrete structure could facilitate the spatial separation of redox reaction sites as well as photogenerated charges. The high surface area of BiFeO3/Bi2WO6 DH-NFs might provide more active sites for photocatalytic reaction. Moreover, the BiFeO3/Bi2WO6 DH-NFs possessed good recycling performance owing to the magnetic-separable property derived from the ferromagnetic behavior of BiFeO3.

Flexibly manipulating optical and electrical properties of 2D materials is of great importance to extend their functional applications in the advanced optoelectronic field. Herein, a type II 2D/0D ...

In the past two decades, ZnO related materials and devices are widely used for various applications, such as thin-film transistors, photodetectors, light-emitting diodes, and transparent conductors because ZnO has several appealing features like abundant raw materials, environmental friendliness, wide and direct band gap, high electron mobility, and large exciton bonding energy. Especially, ZnO has been recognized as one of the most promising candidates for substituting commercial transparent conductors ITO which is exploited as transparent electrodes in solar cells and flat planar display and transparent heaters etc. For example, aluminum doped ZnO (AZO) transparent conducting films have been commercialized successfully. However, the figure of merits and stability of ZnO transparent conducting films still need to be further improved in order to meet the strict demands of practical large-scale applications. So far, various techniques have been developed to alleviate that contradiction between conductivity and visible light transmittance. In the past few years, a new strategy called anion and cation co-doping in ZnO has been widely implemented to improve the figure of merit, in which IIIA group elements are used as cation dopants and fluorine is used as anion dopants. It is worth noting that F has several advantages as anion dopant in ZnO. First, fluorine has a similar ionic radius with oxygen, which will avoid large lattice distortion. Second, the substitution for oxygen with fluorine only disturbs the valence band of ZnO and leaves the conduction band unaffected, which is beneficial for achieving high electron mobility. In this review, the latest researches of F and boron, or aluminum, or gallium, or indium co-doped ZnO thin films are summarized from both the theoretical and the experimental aspects. Effects of anion and cation co-doping on the optical and electrical properties and thermal stability of ZnO thin films are systematically discussed. Both theoretical and experimental results show that cation and anion co-doping can effectively improve the conductivity and visible light transmittance, no matter ZnO thin films were prepared by physical vapor deposition or synthesized by chemical solution processs. Taking Al and F co-doped ZnO (AFZO) thin films prepared with pulse laser deposition as an example, the mobility of AFZO thin film was apparently higher than that of Al-doped ZnO at the same carrier concentration. The high carrier mobility of AFZO is due to that the F can passivate the surface defects and acceptor-like complex defects in ZnO. In addition, the highly electronegative F makes the AFZO thin films exhibit excellent thermal stability, e.g. maintaining high conductive even after air-annealing at 600°C. These results indicate that anion and cation co-doping can effectively improve the performance of ZnO transparent conductive thin films and broaden their applications. Despite these exciting achievements, challenges still remain in the field of anion and cation co-doped ZnO thin films. For example, the mechanism of the co-doping strategy has not been clarified because the formation energy of intrinsic defects in ZnO is relatively low and the defects configurations for anion and cation co-doping are more complicated than single element doping case. Besides, we are still short of effective techniques and theoretical methods to reveal and simulate the behavior of defect clusters in co-doped ZnO. It is also urgent to establish the industrial standard of ceramic targets for co-doped ZnO to eliminate the discrepancies between different groups. More efforts should also be made in developing new equipment for large-scale manufacturing co-doped ZnO thin films. We hope this paper will provide reference to the readers who are interested in transparent conducting oxides.

By selecting the dielectrics that possess well-matched surface energy components with a semiconductor, the dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT) single crystal FET with the mobility as high as 13 cm $^{{2}}\text{V}^{-{1}}\text{s}^{-{1}}$ is obtained. This high mobility combined with a pregrown single crystal as well as the good stability of DNTT provides an opportunity for fundamental studies of organic electronics. These results provide a general criterion for selection of dielectric self-assembled monolayers for an optimized carrier mobility in single-crystal organic filed-effect transistors, and show a promising method to simplify the dielectric optimization process for the development of next-generation high-performance flexible electronics.

Stress induced phase transformation from hexagonal close-packed titanium (HCP-Ti) to face-centered cubic titanium (FCC-Ti) is believed to be a reason for the pronounced work hardening of carbon nanotube-reinforced titanium (CNT/Ti) composites prepared by high-pressure torsion (HPT). Here, the correlation between the phase transformation from the HCP-Ti to the FCC-Ti structure in Ti and the improved mechanical properties of CNT/Ti composite is revealed by investigating the structural transformation mechanism, the stability, electronic properties, anisotropic elasticity and thermodynamics of the FCC-Ti and HCP-Ti crystals under pressure of 0–15GPa by means of first-principles calculations and comparing with the experimental findings. The results show that the formation enthalpies △HTi, the bulk modulus B, the shear modulus G and the Young's modulus E of the FCC-Ti and HCP-Ti structures gradually increase with increasing pressure, and the hybridization between the electronic orbitals of the atoms becomes stronger. The Young’s modulus of the cubic FCC-Ti structure shows strong anisotropy along the [0 1 0] and [1 1 ¯ 0] directions, while the HCP-Ti structure exhibits an obvious anisotropy of E in the (1 0 0) crystal plane. The thermodynamic stability of the HCP-Ti and FCC-Ti structures decreases under high pressure. The different relative stability of the two structures results in a high propensity of structural transformation from the HCP-Ti to the FCC-Ti structure. A large number of FCC-Ti structures are prepared, which can effectively improve the mechanical properties of CNT/Ti composites. Our results may help to better understand the phase transition from HCP-Ti to FCC-Ti under high pressure, and may reveal the structure-property relationship of CNT/Ti composites.

Carrier-exciton interactions in two-dimensional transition metal dichalcogenides (TMDs) is one of the crucial elements for limiting the performance of their optoelectronic devices. Here, we have experimentally studied the carrier-exciton interactions in a monolayer MoS2-based two-terminal device. Such two-terminal device without a gate electrode is generally considered as invalid to modulate the carrier concentration in active materials, while the photoluminescence peak exhibits a red shift and decay with increasing applied voltages. Time-resolved photoluminescence spectroscopy and photoluminescence multipeak fittings verify that such changes of photoluminescence peaks result from enhanced carrier-exciton interactions with increasing electron concentration induce the charged exciton increasing. To characterize the level of the carrier-exciton interactions, a quantitative relationship between the Raman shift of out-of-plane mode and changes in electron concentration has been established using the mass action model. This work provides an appropriate supplement for understanding the carrier-exciton interactions in TMD-based two-terminal optoelectronic devices.

The intrinsic properties and the damage behavior of powder metallurgy (P/M) connecting rod preform have significant effects on its metal flow behavior during flashless forging into its final complex shape with substantial densification. The P/M material constitutive equation were established using isothermal compression tests, and then used to study the metal flow behavior of a P/M connecting rod preform during flashless forging based on finite element modelling (FEM). Moreover, the preform geometry was designed based on these metal flow mechanisms. Experiments and flashless forging of P/M connecting rod preforms were performed in order to verify the accuracy of the simulations. The simulated results are well consistent with the experimental results. Results showed that the shank is much more prone to cracking due to the higher deformation rate and the faster cooling rate. The optimal dimensions of the P/M preform were obtained. When the preform geometry are optimized, the average density of the connecting rod increases homogeneously, and becomes superior to that of the original shape. This work suggests that the geometry of the preform can be designed efficiently based on our models. This work can help to derive a P/M connecting rod preform optimization methodology, which can offer the possibility of improving the quality of the connecting rods efficiently. Keywords: Connecting rod, Numerical simulation, Optimization, Powder metallurgy

Solution processibility is a unique superiority of organic semiconductors, which provides tremendous potential for the low-cost production of wearable and implantable electronics. However, the solution affinity to the substrate surface remains a serious dilemma due to the difficulty of liquid manipulation on hydrophobic surfaces, but the use of such surfaces is essential to improve device performance. Here, we applied a new-type additive, non-ionic fluorosurfactant, to add into the organic semiconductor solution. It not only can effectively improve the wettability of the low-viscosity solution on the hydrophobic surface, but also enhance the field-effect performance of the fabricated poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b’]dithophen-2-yl)-alt-[1, 2, 5]- thiadiazolo[3,4-c]pyridine] organic thin-film transistors (OTFTs) by forming vertical phase separation. Combined with the nanogrooved octadecyltrichlorosilane/SiO2, the obtained OTFTs exhibit excellent field-effect characteristics with mobility as high as 4.02 cm2V−1s−1, which far surpasses that of modern industrial amorphous silicon. This work provides a simple strategy to prepare continuous and uniform organic semiconductor thin film on the hydrophobic surface, indicating promising potential for future high-performance solution-processed organic electronic devices.

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have drawn worldwide attention for their promising photovoltaics performance and earth-abundant element composition, yet the record efficiency of this type of device is still far lower than its theoretical conversion efficiency. Undesirable band alignment and severe non-radiative recombination at CZTSSe/CdS heterojunction interfaces are the major causes limiting the current/voltage output and overall device performance. Herein, we propose a novel two-step CdS deposition strategy to improve the quality of CZTSSe/CdS heterojunction interface and thereby improve the performance of CZTSSe solar cell. The two-step strategy includes firstly pre-deposits CdS thin layer on CZTSSe absorber layer by chemical bath deposition (CBD), followed with a mild heat treatment to facilitate element inter-diffusion, and secondly deposits an appropriate thickness of CdS layer by CBD to cover the whole surface of pre-deposited CdS and CZTSSe layers. The solar energy conversion efficiency of CZTSSe solar cells with two-step deposited CdS layer approaches to 8.76% (with an active area of about 0.19 cm2), which shows an encouraging improvement of over 87.98% or 30.16% compared to the devices with traditional CBD-deposited CdS layer without and with the mild annealing process, respectively. The performance enhancement by the two-step CdS deposition is attributed to the formation of more favorable band alignment at CZTSSe/CdS interface as well as the effective decrease in interfacial recombination paths on the basis of material and device characterizations. The two-step CdS deposition strategy is simple but effective, and should have large room to improve the quality of CZTSSe/CdS heterojunction interface and further lift up the conversion efficiency of CZTSSe solar cells.

Highly effective utilization of solar light is very important for water treatment via photocatalysis. To achieve this goal, we designed and synthesized an efficient full-spectrum-response photocata...

Photochromic materials present photocontrollable properties, which is of great interest for potential applications including high-density storage and optical displays. Herein, we demonstrate a promising pathway toward smart photochromic nanocomposite exploration by anchoring of carbon dots (CDs) to titanium dioxide (TiO2) porous films. This study reveals that the color of the CDs/TiO2 film obtained by dropping anchoring becomes darker and that obtained by immersion anchoring becomes lighter, both under blue light irradiation. For the photobleaching material system, the spectral response is strongly dependent on wavelength and polarization of the exciting light, which provides new dimensions for optical information encryption and memory. This work lays the foundation for the materials platform in the integration of advanced information processing in the future.

Natural biomaterials have recently attracted growing interest in the construction of artificial synaptic transistors, since as-fabricated electronic devices are typically sustainable, biodegradable, biocompatible, and metabolizable. Most importantly, proton conduction has been discovered in a variety of polyelectrolyte-type natural biomaterials, and the protons mainly originate from the ionizable groups of such materials themselves. However, the previous theory is not applicable to neutral natural biomaterials, whose groups in their molecular chains can hardly dissociate ions. Here, we construct a biodegradable organic synaptic transistor based on neutral-polysaccharide dielectric, and explore the influence of water content and hydroxyl content on the proton conduction behavior. Our results suggest that protons originate from the self-dissociation of water, and then migrate along a continuous hydrogen-bond network under the electric field. Furthermore, natural polysaccharides, with the unique traits of biodegradability, biocompatibility and solubility, allow the preparation of biodegradable and ultraflexible organic synaptic transistors. Therefore, our devices can conformally adhere to various uneven surfaces and degrade in water harmlessly after their programmed lifetime. This study paves a new way to develop “green” and soft artificial nervous systems, providing a meaningful guidance for synaptic transistors based on neutral polymers and expanding the possibility of applying neutral biomaterials to neuromorphic systems.

Optoelectronic resistive switching (RS) devices are attracting attention due to their promising potential in optical communication technology. In this study, a photo-tunable organic memory device based on poly(4-vinylphenol) (PVP) and N-doped carbon quantum dot nanocomposites is presented. After UV light irradiation, the set voltage of the device can be gradually reduced by adjusting the irradiation time. This memory device presents excellent memory performance after large-angle bending or repetitive bending tests. More importantly, the controlled switching voltage characteristic enabled the realization of encrypted image storage. Raman spectra evidence that a local conductive sp2-hybridized carbon region was generated through UV light reduction, which can effectively enhance the internal electrical field and shorten the tunneling distance between the carbon dots, thus decreasing the set voltage. Our work provides a new approach towards the development of photo-tunable organic memory for future wearable optoelectronic neuromorphic computing systems.

Commercial applications of skin-like electronic devices for healthcare, intelligent robotics and electronic communication require large-scale high-density transistor arrays with high mechanical deformability and robustness that can be provided by intrinsically stretchable transistors. However, the contradictory crystallinity-dominated mobility and stretchability in the currently reported polymer semiconductors result in extremely limited high-mobility intrinsically stretchable transistors. Herein, based on a polymer with strong intrachain transport, we pioneer the use of molecular weight modulation to synchronously achieve increased mobility from 0.56 to 1.95 cm2 V−1 s−1 and increased crack-onset strain from 26 to 97% in the PIDTBT film. Based on the molecular weight modulation, a high-performance intrinsically stretchable transistor array with stretchability up to 100 percent strain and mobility up to 1.84 cm2 V−1 s−1, was demonstrated. Moreover, the stretchable transistor array presents a device density as high as 375 devices per square centimeter and good electrical performance at the static and dynamic stretching strain. Our results provide a new strategy for creating intrinsically stretchable transistors with high mobility and present unprecedented opportunities for large-scale high-density production of next-generation stretchable electronics.

Photocatalysis shows great promise in the field of solar energy conversion. One of the reasons for this is because it promotes the development of multi-field-coupled catalysis. In order to explore the principles of multi-field-coupled catalytic reactions, an in situ multi-field-coupled characterization technique is required. In this study, we obtained hydrogenated ST-01 TiO2 and observed enhanced catalytic activity by thermal coupled photocatalysis. In situ photoconductivity was employed to understand the activity enhancement. The effects of the reaction temperature, reaction atmosphere, and oxygen vacancy (Ov) on the photoconductivity of TiO2 were studied. After coupling thermal into photoconductivity measurement, highly active Ov-TiO2 displayed rapid decay of photoconductivity in a CO2 atmosphere and slow decay of photoconductivity in a N2 atmosphere. These phenomena revealed that photothermal coupling assisted the detrapping of electrons at the Ov surface and promoted electron transfer to CO2, which clearly explained the high photothermal catalytic activity of Ov-TiO2. This study demonstrated that photoconductivity is a useful tool to help understand photothermal catalytic phenomena.

TiO2/SrTiO3/g-C3N4 ternary heterojunction nanofibers with a cascade energy band alignment were designed and then fabricated by a combination of electrospinning technology and gas-solid reaction. Their photocurrent responses were 1.4 and 1.8 times higher while their transient photoluminescence lifetime were about 0.75 and 0.79 times shorter than those of TiO2/g-C3N4 nanofibers and SrTiO3/g-C3N4 nanofibers, respectively. The enhanced photocurrent response, decreased lifetime, and their dramatically decreased photoluminescence intensity clearly indicated that highly efficient cascade charge transfer and separation were achieved in the ternary nanofibers with the gradient energy band alignment compared with the corresponding traditional binary nanofibers noted above. When tested in photocatalytic reduction reactions of H2 evolution and nitrogen fixation, the corresponding reaction rates under simulated sunlight irradiation values of 1304 μmol g-1 h-1 and 2192 μmol g-1 h-1 L-1 were 2.1 and 1.9 times better than those of TiO2/g-C3N4 nanofibers and 4.2 and 3.3 times better than those of SrTiO3/g-C3N4 nanofibers, respectively. Furthermore, the photocatalytic activities of the TiO2/SrTiO3/g-C3N4 nanofibers had no significant decrease after several cycles, indicating that they possessed good structural stability properties. This work provides a new route to design and fabricate an efficient photocatalyst for photocatalytic reduction reactions.

Developing a conceptual “write”/“read” technology for optical information storage of persistent phosphors is necessary but often underestimated. Here we demonstrate a “write”/“read” approach of traps upon illumination by using a blue light-emitting diode (LED) in persistent phosphors such as LaMgGa11O19:Cr3+. Our investigation indicates that the phosphor can be charged upon high-power illumination (e.g., incident power density of 0.5 W cm−2) but discharged upon low-power illumination (e.g., 0.1 W cm−2). An appealing feature of the present approach is that the charging and discharging share the same illumination wavelength, which offers an interesting technical advantage and apparent convenience for applications. Moreover, such a manipulation technique is generally applicable for many existing phosphors.

Stretchable lithium ion batteries receive considerable attention due to their promising application to meet the growing demand of wearable portable electronics. Despite tremendous efforts being made to fabricate stretchable lithium ion batteries, challenges remain due to the complicated fabrication process, high fabrication cost, and low mass loading. Herein, a simple design concept for all-stretchable-component lithium ion batteries via an all solution process is reported. All components are stretchable, including Li4Ti5O12 (LTO) and LiFePO4 (LFP) electrodes based on the 3D polydimethylsiloxane (PDMS)/single-wall carbon nanotube (SWCNT) porous framework, poly(vinylidene fluoride-co-hexa-fluoropropylene) (PVDF-HFP) gel separator, and PDMS package. The prepared electrodes based on the versatile 3D PDMS/SWCNT porous framework show many superior merits, such as high mass loading, good stretchability, outstanding mechanical durability, and high conductivity. More impressively, the mass loading of our electrode materials is as high as 7 mg cm−2, which is higher than that of all the reported all-stretchable-component lithium ion batteries. The resulting practical capacity is improved significantly up to 0.81 mA h cm−2 at 0.069C. The full cell delivers a high capacity of 0.66 mA h cm−2 even after 100 stretch–release cycles of 50% tensile strain at 0.075C, and shows a stable power supply during various extreme deformations. This work opens a feasible route to construct all-stretchable-component lithium ion batteries with high electrochemical performance and high stretchability, presenting promising potential for application in new-generation wearable and portable energy storage devices.

Highly transparent and active Pt-Mo2C counter electrodes were successfully fabricated by the strong metal-support interaction, with high dispersity of Pt nanoclusters on Mo2C support, which endowed bifacial dye-sensitized solar cells with a rear-to-front efficiency ratio as high as 0.75.

Oxygen vacancies (VO) often exist in wide-bandgap metal oxide semiconductors (MOSs) as deep-level defects and undermine the reliability of various optoelectronic devices based on MOSs. Conventional methods to passivate VO defects, such as high-temperature annealing or plasma treatment, can compromise device performance. This work demonstrates that passivation of VO defects in aluminum-doped ZnO (AZO) nanoparticles can be realized through low-temperature annealing (350 °C) in an NF3 atmosphere. After the NF3 annealing, the longitudinal optical phonon scattering mode in Raman spectroscopy, the visible light emission intensity in photoluminescence spectroscopy, and the oxygen deficiency-related peak in x-ray photoelectron spectroscopy decrease simultaneously, indicating the passivation of VO defects in AZO nanoparticles. As a result, AZO nanoparticles show higher visible light reflectance and better stability of electrical conductivity owing to the suppression of deep-level light absorption and gas molecule adsorption. This work also offers insights into the passivation mechanism of VO defects in MOSs.

Doctors usually diagnose patients based on their symptoms or medical investigation results, yet useful supplemental information such as living style behaviors and daily nutrition intake prior to th...

Field monitoring programs (e.g., convergence measurements and stress measurements in the support system) play an important role in following the response of the ground and of the support s...

Optoelectronic synapses are considered to be important cornerstones in the construction of neuromorphic computing systems because of their low power consumption, high operating speeds, and high scalability. In this work, we demonstrate an optoelectronic synaptic device based on a ZnO/HfOx heterojunction in which optical potentiation/electrical depression behaviors and nonvolatile high current state can be implemented. The heterojunction device exhibits conductance evolution with high linearity. The excellent optoelectronic memristive behavior of the device can be attributed to the interface barrier between ZnO and HfOx, which hinders the recombination of photo-excited electron–hole pairs to increase the carrier lifetime, and realizes the nonvolatile high current state. More importantly, the artificial vision system based on optoelectronic synaptic devices can achieved a high recognition accuracy of 96.1%. Our work provides a feasible pathway toward the development of optoelectronic synaptic devices for use in high-performance neuromorphic vision systems.