Design and tailoring of patterned ZnO nanostructures for perovskite light absorption modulation

Lithography is a pivotal micro/nanomanufacturing technique,facilitating performance enhancements in an extensive array of devices,encompassing sensors,transistors,and photovoltaic devices.The key to creating highly precise,multiscale-distributed patterned structures is the precise control of the lithography process.Herein,high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography.By optimizing these parameters,ZnO nanorod arrays with line/hole arrangements are successfully prepared.Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure,enlarged surface area,and improved light capture ability,which achieve highly efficient energy conversion in perovskite solar cells.The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.

Conformal Human–Machine Integration Using Highly Bending‑Insensitive,Unpixelated,and Waterproof Epidermal Electronics Toward Metaverse

Efficient and flexible interactions require precisely converting human intentions into computer-recognizable signals,which is critical to the breakthrough development of metaverse.Interactive electronics face common dilemmas,which realize highprecision and stable touch detection but are rigid,bulky,and thick or achieve high flexibility to wear but lose precision.Here,we construct highly bending-insensitive,unpixelated,and waterproof epidermal interfaces(BUW epidermal interfaces)and demonstrate their interactive applications of conformal human–machine integration.The BUW epidermal interface based on the addressable electrical contact structure exhibits high-precision and stable touch detection,high flexibility,rapid response time,excellent stability,and versatile“cut-and-paste”character.Regardless of whether being flat or bent,the BUW epidermal interface can be conformally attached to the human skin for real-time,comfortable,and unrestrained interactions.This research provides promising insight into the functional composite and structural design strategies for developing epidermal electronics,which offers a new technology route and may further broaden human–machine interactions toward metaverse.

Dynamic behavior of tunneling triboelectric charges in two-dimensional materials

Although the research history of triboelectrification has been more than 2000 years, there are still many problems to be solved so far.The use of scanning probe microscopy provides an important way to quantitatively study the transfer, accumulation, and dissipation of triboelectric charges in the process of triboelectrification. Two-dimensional materials are considered to be key materials for new electronic devices in the post-Moore era due to their atomic-scale size advantages. If the electrostatic field generated by triboelectrification can be used to replace the traditional gate electrostatic field, it is expected to simplify the structure of two-dimensional electronic devices and reconfigure them at any time according to actual needs. Here, we investigate the triboelectrification process of various two-dimensional materials such as MoS_(2), WSe_(2),and ZnO. Different from traditional bulk materials, after two-dimensional materials are rubbed, the triboelectric charges generated may tunnel through the two-dimensional materials to the underlying substrate surface. Because the tunneling triboelectric charge is protected by the twodimensional material, its stable residence time on the substrate surface can reach more than 7 days, which is more than tens of minutes for the traditional triboelectric charge. In addition, the electrostatic field generated by the tunneling triboelectric charge can effectively regulate the carrier transport performance of two-dimensional materials, and the source–drain current of the field effect device regulated by the triboelectric floating gate is increased by nearly 60 times. The triboelectric charge tunneling phenomenon in two-dimensional materials is expected to be applied in the fields of new two-dimensional electronic devices and reconfigurable functional circuits.

Architecture Design and Interface Engineering of Self-assembly VS_(4)/rGO Heterostructures for Ultrathin Absorbent

The employment of microwave absorbents is highly desirable to address the increasing threats of electromagnetic pollution.Importantly,developing ultrathin absorbent is acknowledged as a linchpin in the design of lightweight and flexible electronic devices,but there are remaining unprecedented challenges.Herein,the self-assembly VS_(4)/rGO heterostructure is constructed to be engineered as ultrathin microwave absorbent through the strategies of architecture design and interface engineering.The microarchitecture and heterointerface of VS_(4)/rGO heterostructure can be regulated by the generation of VS_(4) nanorods anchored on rGO,which can effectively modulate the impedance matching and attenuation constant.The maximum reflection loss of 2VS_(4)/rGO40 heterostructure can reach−43.5 dB at 14 GHz with the impedance matching and attenuation constant approaching 0.98 and 187,respectively.The effective absorption bandwidth of 4.8 GHz can be achieved with an ultrathin thickness of 1.4 mm.The far-reaching comprehension of the heterointerface on microwave absorption performance is explicitly unveiled by experimental results and theoretical calculations.Microarchitecture and heterointerface synergistically inspire multi-dimensional advantages to enhance dipole polarization,interfacial polarization,and multiple reflections and scatterings of microwaves.Overall,the strategies of architecture design and interface engineering pave the way for achieving ultrathin and enhanced microwave absorption materials.

A high-sensitive and self-selective humanoid mechanoreceptor for spatiotemporal tactile stimuli cognition

The cognition of spatiotemporal tactile stimuli,including fine spatial stimuli and static/dynamic temporal stimuli,is paramount for intelligent robots to feel their surroundings and complete manipulation tasks.However,current tactile sensors have restrictions on simultaneously demonstrating high sensitivity and performing selective responses to static/dynamic stimuli,making it a challenge to effectively cognize spatiotemporal tactile stimuli.Here,we report a high-sensitive and self-selective humanoid mechanoreceptor(HMR)that can precisely respond to spatiotemporal tactile stimuli.The HMR with PDMS/chitosan@CNTs(PDMS:polydimethylsiloxane;CNT:carbon nanotube)graded microstructures and polyurethane hierarchical porous spacer exhibits high sensitivity of 3790.8 kPa^(-1).The HMR demonstrates self-selective responses to static and dynamic stimuli with mono signal through the hybrid of piezoresistive and triboelectric mechanisms.Consequently,it can respond to spatiotemporal tactile stimuli and generate distinguishable and multi-type characteristic signals.With the assistance of the convolutional neural network,multiple target objects can be easily identified with a high accuracy of 99.1%.This work shows great potential in object precise identification and dexterous manipulation,which is the basis of intelligent robots and natural human-machine interactions.

Service behavior of triboelectric nanogenerators:Bridging the gap between prototypes and applications

The triboelectric nanogenerators(TENGs),suppling power for freely mobile and distributed electronic equipment from Internet of Things,have been considered as“the energy for the new era”.Research on the service behavior has become increasingly important for achieving the reliability evaluation and life prediction of TENGs,as TENGs advance from prototypes to practical applications.Due to the wide selection of materials,the diversity of device structures,and the complexity of working environment,TENGs show unique characteristics in the service behavior.These dilemmas lead to the fact that systematical summary of service behavior for TENGs is still in its infancy.Here,the progresses of the service behavior for TENGs are comprehensively reviewed from the influence of environmental factors on the service performance of TENGs to the impact of TENGs during the service on their surroundings.We summed up the performance evolution of TENGs in the real environment and the reproducibility of TENGs of which the electrical output will be restored after failure.Then,the service adaptability of TENG is systematically discussed,including the biological and environmental compatibility.Finally,the challenges and opportunities that the related research faced are proposed to promote the emerging technology from laboratory to factory.

ZnO纳米结构及其在钙钛矿光伏电池中的应用

近年来,有机-无机杂化钙钛矿光伏电池取得了突飞猛进的发展,已成为光伏领域的研究焦点;其光伏性能的不断提高不仅与钙钛矿材料自身质量与光电特性的提升有关,同时依赖于载流子传输层的优化与设计.鉴于ZnO的优势和特性,本文聚焦于ZnO纳米结构设计及其在钙钛矿光伏电池中的应用,简述了ZnO材料独特的光电性质,总结了ZnO纳米结构的制备方法及合成原理;详细综述了不同维度ZnO纳米结构在钙钛矿光伏电池中的发展进程,着重阐述了化学掺杂、表面修饰、应力调控策略在ZnO基钙钛矿光伏电池性能优化方面的研究进展.本文系统总结了ZnO电子传输层的国内外研究现状、应用前景及发展趋势,为设计构筑高性能ZnO基钙钛矿光伏电池提供了重要的指导.

Electromagnetic wave absorption in reduced graphene oxide functionalized with Fe3O4/Fe nanorings

We report the preparation of nanocomposites of reduced graphene oxide with embedded Fe3O4/Fe nanorings （FeNR@rGO） by chemical hydrothermal growth. We illustrate the use of these nanocomposites as novel electromagnetic wave absorbing materials. The electromagnetic wave absorption properties of the nanocomposites with different compositions were investigated. The preparation procedure and nanocomposite composition were optimized to achieve the best electromagnetic wave absorption properties. Nanocomposites with a GO：cx-Fe203 mass ratio of 1：1 prepared by annealing in HdAr for 3 h exhibited the best properties. This nanocomposite sample （thickness = 4.0 mm） showed a minimum reflectivity of -23.09 dB at 9.16 GHz. The band range was 7.4-11.3 GHz when the reflectivity was less than -10 dB and the spectrum width was up to 3.9 GHz. These figures of merit are typically of the same order of magnitude when compared to the values shown by traditional ferric oxide materials. However, FeNR@rGO can be readily applied as a microwave absorbing material because the production method we propose is highly compatible with mass production standards.

Investigation on the broadband electromagnetic wave absorption properties and mechanism of Co3O4- nanosheets/reduced-graphene-oxide composite

A cobaltosic-oxide-nanosheets/reduced-graphene-oxide composite （CoNSs@RGO） was successfully prepared as a light-weight broadband electromagnetic wave absorber. The effects of the sample thickness and amount of composite added to paraffin samples on the absorption properties were thoroughly investigated. Due to the nanosheet-like structure of Co3O4, the surface-to-volume ratio of the wave absorption material was very high, resulting in a large enhancement in the absorption properties. The maximum refection loss of the CoNSs@RGO composite was -45.15 dB for a thickness of 3.6 mm, and the best absorption bandwidth with a reflection loss below -10 dB was 7.14 GHz with a thickness of 2.9 mm. In addition, the peaks of microwave absorption shifted towards the low frequency region with increasing thickness of the absorbing coatings. The mechanism of electromagnetic wave absorption was attributed to impedance matching of CoNSs@RGO as well as the dielectric relaxation and polarization of RGO. Compared to previously reported absorbing materials, CoNSs@RGO showed better performance as a lightweight and highly efficient absorbing material for application in the high frequency band.

Flexible piezoelectric nanogenerators based on a fiber/ZnO nanowires/paper hybrid structure for energy harvesting

We present a novel, low-cost approach to fabricate flexible piezoelectric nano- generators （NGs） consisting of ZnO nanowires （NWs） on carbon fibers and foldable Au-coated ZnO NWs on paper. By using such designed structure of the NGs, the radial ZnO NWs on a cylindrical fiber can be utilized fully and the electrical output of the NG is improved. The electrical output behavior of the NGs can be optionally controlled by increasing the fiber number, adjusting the strain rate and connection modes. For the single-fiber based NGs, the output voltage is 17 mV and the current density is about 0.09 μA·cm^-2, and the electrical output is enhanced greatly compared to that of previous similar micro-fiber based NGs. Compared with the single-fiber based NGs, the output current of the multi-fiber based NGs made of 200 carbon fibers increased 100-fold. An output voltage of 18 mV and current of 35 nA are generated from the multi-fiber based NGs. The electrical energy generated by the NGs is enough to power a practical device. The developed novel NGs can be used for smart textile structures, wearable and self-powered nanodevices.

Enhanced microwave absorption performance of highly dispersed CoNi nanostructures arrayed on graphene

Magnetic metals （Fe, Co, Ni） and alloys thereof are easily synthesized as nanoparticles, but obtaining highly dispersed graphene-based magnetic nanomaterials remains challenging. Here, three CoNi/graphene nanocomposites （CoNi/GN） are successfully assembled for the first time via a one-pot strategy without templating by manipulating the reaction time and solvents used for the same precursors. Moreover, the reduction of graphene oxide utilizing this method is more effective than that by conventional methods and the alloy particles are firmly embedded on the GN substrate. Compared to n- and p-CoNi/GN nanocomposites, o-CoNi/GN nanocomposites show the best electromagnetic wave absorption properties with the maximum reflection loss of -31.0 dB at 4.9 GHz for a thickness of 4 mm; the effective absorption bandwidth （〈 10.0 dB） is 7.3 GHz （9.5-16.8 GHz） for a thickness of 2 mm. The structures and electromagnetic wave absorption mechanisms of the three composites were also investigated. This research provides a new platform for the development of magnetic alloy nanoparticles in the field of microwave-absorbing devices.

Novel perovskite/TiO2/Si trilayer heterojunctions for high-performance self-powered ultraviolet-visible-near infrared （UV-Vis-NIR） photodetectors

Methylammonium lead halide perovskites have been reported to be promising candidates for high-performance photodetectors. However, self-powered broadband ultraviolet-visible-near infrared （UV-Vis-NIR） photodetection with high responsivity is difficult to achieve in these materials. Here, we demonstrate, for the first time, a novel trilayer hybrid photodetector made by combining an n-type Si wafer, TiO2 interlayer and perovskite film. By precisely controlling the thickness of the TiO2 layer, enhanced separation and reduced recombination of carriers at the Si-perovskite interface are obtained. As a result, perovskite film, when combined with a low-bandgap Si, extends the wavelength range of photo response to 1,150 nm, along with improved on/off ratio, responsivity, and specific detectivity, when compared to pristine perovskite. Results obtained in this work are comparable or even better than those reported for perovskite-based UV-Vis-NIR photodetectors. In particular, the hybrid photodetectors can operate in a self- powered mode. The mechanism of enhancement has been explored and it is found that the increased separation and reduced recombination of photogenerated carriers at the junction interface leads to the improved performance.

Development, applications, and future directions of triboelectric nanogenerators

Since the invention of the triboelectric nanogenerator （TENG） in 2012, it has become one of the most vital innovations in energy harvesting technologies. The TENG has seen enormous progress to date, particularly in applications for energy harvesting and self-powered sensing. It starts with the simple working principles of the triboelectric effect and electrostatic induction, but can scavenge almost any kind of ambient mechanical energy in our daily life into electricity. Extraordinary output performance optimization of the TENG has been achieved, with high area power density and energy conversion efficiency. Moreover, TENGs can also be utilized as self-powered active sensors to monitor many environmental parameters. This review describes the recent progress in mainstream energy harvesting and self-powered sensing research based on TENG technology. The birth and development of the TENG are introduced, following which structural designs and performance optimizations for output performance enhancement of the TENG are discussed. The major applications of the TENG as a sustainable power source or a self-powered sensor are presented. The TENG, with rationally designed structures, can convert irregular and mostly low-frequency mechanical energies from the environment, such as human motion, mechanical vibration, moving automobiles, wind, raindrops, and ocean waves. In addition, the development of self-powered active sensors for a variety of environmental simulations based on the TENG is presented. The TENG plays a great role in promoting the development of emerging Internet of Things, which can make everyday objects connect more smartly and energy- efficiently in the coming years. Finally, the future directions and perspectives of the TENG are outlined. The TENG is not only a sustainable micro-power source for small devices, but also serves as a potential macro-scale generator of power from water waves in the future.

Strain-modulation and service behavior of Au-MgO-ZnO ultraviolet photodetector by piezo-phototronic effect

Au-MgO-ZnO （AMZ） ultraviolet （UV） photodetectors were fabricated to enhance their sensitivities by an inserting ultrathin insulating MgO layer. With the insulating layer, the sensitivities of the UV photodetectors were improved via the reduction of the dark current. Furthermore, strain modulation was used to enhance the sensitivities of the AMZ UV photodetectors. The sensitivities of the photodetectors were enhanced by the piezo-phototronic effect. However, there was a limiting value of the applied strains to enhance the sensitivity of the photodetector. When the external strains exceeded the limiting value, the sensitivity decreased because of the tunneling dark current. The external strains loaded on the photodetectors result in the degradation of the photodetectors, and an applied bias can accelerate the process. This work presents a prospective approach to engineer the performance of a UV photodetector. In addition, the study on the service behavior of the photodetectors may offer a strain range and theoretical support for safely using and studying metal-insulator-semiconductor （MIS） UV photodetectors.

Functional nanogenerators as vibration sensors enhanced by piezotronic effects

ZnO nanomaterials have been shown to have novel applications in optoelectronics, energy harvesting and piezotronics, due to their coupled semiconducting and piezoelectric properties. Here a functional nanogenerator （FNG） based on ZnO nanowire arrays has been fabricated, which can be employed to detect vibration in both self-powered （SP） and external-powered （EP） modes. In SP mode, the vibration responses of the FNG can be measured through converting mechanical energy directly into an electrical signal. The FNG shows consistent alternating current responses （relative error 〈 0.37%） at regular frequencies from 1 to 15 Hz. In EP mode, the current responses of FNG are significantly enhanced via the piezotronic effect. Under a forward bias of 3 V, the sensor presented a sensitivity of 3700% and an accurate measurement （relative error 〈 0.91%） of vibration frequencies in the range 0.05-15 Hz. The results show that this type of functional nanogenerator sensor can detect vibration in both SP and EP modes according to the demands of the applications.

Gold nanoparticle/ZnO nanorod hybrids for enhanced reactive oxygen species generation and photodynamic therapy

Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet （UV） irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a ＂1 ＋ 1 〉 2 effect.＂ This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO：Au ratio of 20：1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid （20：1, 100 μg/mL） resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.

The enhanced performance of piezoelectric nanogenerator via suppressing screening effect with Au particles/ZnO nanoarrays Schottky junction

This paper describes a novel strategy to weaken the piezopotential screening effect by forming Schottky junctions on the ZnO surface through the introduction of Au particles onto the surface. With this approach, the piezoelectric-energyconversion performance was greatly enhanced. The output voltage and current density of the Au@ZnO nanoarray-based piezoelectric nanogenerator reached 2 V and 1 μA/cm^2, respectively, 10 times higher than the output of pristine ZnO nanoarray-based piezoelectric nanogenerators. We attribute this enhancement to dramatic suppression of the screening effect due to the decreased carrier concentration, as determined by scanning Kelvin probe microscope measurements and impedance analysis. The lowered capacitance of the Au@ZnO nanoarraybased piezoelectric nanogenerator also contributes to the improved output. This work provides a novel method to enhance the performance of piezoelectric nanogenerators and possibly extends to piezotronics and piezophototronics.

Kelvin probe force microscopy for perovskite solar cells

Kelvin probe force microscopy(KPFM) could identify the local work function of surface at nanoscale with high-resolution on the basis of simultaneous visualization of surface topography, which provides a unique route to in-situ study of the surface information like the composition and electronic states. Currently, as a non-destructive detection protocol, KPFM demonstrates the unique potential to probe the basic nature of perovskite materials that is extremely sensitive to water, oxygen and electron beam irradiation. This paper systematically introduces the fundamentals and working mode of KPFM, and elaborates the promising applications in perovskite solar cells for energy band structures and carrier transport dynamics, trap states, crystal phases, as well as ion migration explorations. The comprehensive understanding of such potential detection engineering may provide novel and effective approaches for unraveling the unique properties of perovskite solar cells.

Synergistic-engineered van der Waals photodiodes with high efficiency

Van der Waals(vdW)heterostructures based on two-dimensional transitionmetal dichalcogenides have provided unprecedented opportunities for photovoltaic detectors owing to their strong light-matter interaction and ultrafast interfacial charge transfer.Despite continued advancement,insufficient control of photocarrier behaviors still limits the external quantum efficiency(EQE)and operation speed of such detectors.Here,we propose a synergistic strategy of contact-configuration design and thickness-modulation to construct high-performance vdW photodiodes based on the typical type II heterostructure(MoS2/WSe2).Through integrating three contact architectures into one device to exclude other factors,we solid the superiority of designed 1L-MoS2/WSe2/graphene heterostructures incorporating efficient photocarrier collection and gate modulation.Together with leveraging the layer-numberdependent properties of WSe2,we observe the critical thickness of WSe2(11 layers)for the highest EQE,which verifies the thickness-dependent competition between photocarrier generation,dissociation,and collection.Finally,we demonstrate the synergistic-engineered vdW heterostructure can trigger record-high EQE(61%)and manifest ultrafast photoresponse(4.1μs)at the atomically thin limit(8 nm).The proposed strategy enables architecture-design and thickness-engineering to unlock the potential to realize high-performance optoelectronic devices.

Strain modulation on graphene/ZnO nanowire mixed- dimensional van der Waals heterostructure for high- performance photosensor

The mixed-dimensional van der Waals （vdW） heterostructure is a promising building block for strained electronics and optoelectronics because it avoids the bond fracture and atomic reconstruction under strain. We propose a novel mixed-dimensional vdW heterostructure between two-dimensional graphene and a one-dimensional ZnO nanowire for high-performance photosensing. By utilizing the piezoelectric properties of ZnO, strain modulation was accomplished in the mixed-dimensional vdW heterostructure to optimize the device performance. By combining the ultrahigh electrons transfer speed in graphene and the extremely long life time of holes in ZnO, an outstanding responsivity of 1.87 ×10^5 A/W was achieved. Under a tensile strain of only 0.44% on the ZnO nanowire, the responsivity was enhanced by 26%. A competitive model was proposed, in which the performance enhancement is due to the efficient promotion of the injection of photogenerated electrons from the ZnO into the graphene caused by the strain-induced positive piezopotential. Our study provides a strain-engineering strategy for controlling the behavior of the photocarriers in the mixed-dimensional vdW heterostructure, which can be also applied to other similar systems in the future.