Spatially Bandgap-Graded Mo S2（1-x）Se2x Homojunctions for Self-Powered Visible–Near-Infrared Phototransistors

Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features,which opens up new potential for device applications.Here,visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys,synthesized by a simple and controllable chemical solution deposition method,are reported.The graded bandgaps,arising from the spatial grading of Se composition and thickness within a single domain,are tuned from 1.83 to 1.73 eV,leading to the formation of a homojunction with a builtin electric field.Consequently,a strong and sensitive gate-modulated photovoltaic effect is demonstrated,enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1,a specific detectivity up to^10^11 Jones,and an on/off ratio up to^10^4.Remarkably,when illuminated by the lights ranging from 405 to 808 nm,the biased devices yield a champion photoresponsivity of 191.5 A W−1,a specific detectivity up to^1012 Jones,a photoconductive gain of 10^6–10^7,and a photoresponsive time in the order of^50 ms.These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions.

Flexible cobalt phosphide network electrocatalyst for hydrogen evolution at all pH values

High-performance electrocatalysts for water splitting at all pH values have attracted considerable interest in the field of sustainable hydrogen evolution. Herein, we report an efficient electrocatalyst with a nanocrystalline cobalt phosphide （COP） network for water splitting in the pH range of 0-14. The novel flexible electrocatalyst is derived from a desirable nanocrystalline CoP network grown on a conductive Hastelloy belt. This kind of self-supported CoP network is directly used as an electrocatalytic cathode for hydrogen evolution. The nanocrystalline network structure results in superior performance with a low onset overpotential of N45 mV over a broad pH range of 0 to 14 and affords a catalytic current density of 100 mA-cm 2 even in neutral media. The CoP network exhibits excellent catalytic properties not only at extreme pH values （0 and 14） but also in neutral media （pH = 7）, which is comparable to the behavior of state-of-the-art platinum-based metals. The system exhibits an excellent flexible property and maintains remarkable catalytic stability during continuous 100-h-long electrolysis even after 100 cycles of bending/extending from 100° to 250°.

Defect engineering of molybdenum disulfide through ion irradiation to boost hydrogen evolution reaction performance

The inert basal plane of molybdenum disulfide (MoS2) restrains its further hydrogen evolution reaction (HER) performance.This work attempts ion irradiation to activate inert basal plane of MoS2 nanosheet to improve its electrocatalytic performance.Experimental results demonstrate the sulphur vacancies generated by ion irradiation on the basal plane of MoS2 mainly boost the efficiency of HER performance.The moderate fluence of carbon ion irradiation gains the optimum HER performance with an onset potential of 77 mV and Tafel slope of 66 mV/dec.

Observation of ambipolar photoresponse from 2D MoS_(2)/MXene heterostructure

Two-dimensional materials have been demonstrated as promising toolboxes for optoelectronics.Transition metal carbides and nitrides(MXenes),members of an emerging family of two-dimensional materials,have drawn extensive attention in optoelectronics owing to their excellent conductivity and tunable electronic properties.Herein,a photodetector based on the two-dimensional van der Waals heterostructure of Ti_(3)C_(2)T_(x)MXene and a MoS_(2)monolayer was constructed to observe the ambipolar photoresponse,which showed a positive photoresponse in the visible spectrum(500-700 nm)and a negative photoresponse at longer wavelengths(700-800 nm).The device exhibited a high negative responsivity of 1.9 A/W and a detectivity of 2.1×10^(10)Jones under 750 nm light illumination.Detailed experiments demonstrate that the negative photoresponse arises from the heterostructureinduced trap energy level,which confines the excited photoelectrons and leads to an inverse current.This work demonstrates a unique optoelectronic phenomenon in MoS_(2)/MXene heterostructures and provides valuable insights into the development of new photodetection materials.

多功能二维玻璃态石墨烯器件用于可见光-近红外光探测与挥发性液体传感

本文设计了基于二维玻璃态石墨烯的多功能器件.与本征石墨烯相比,扭曲的晶格结构打开了玻璃态石墨烯的带隙,表现出与石墨烯类似甚至更优异的光电探测与化学传感性能.由于玻璃态石墨烯与空气中的小分子间较强的相互作用,该器件受到光致脱附的影响更小,呈现出正的光响应.在405 nm的激光照射下,器件的响应率为0.22 A W^(-1),探测率为10^(10)Jones.此外,玻璃态石墨烯中的固有缺陷和应变可增强分析物的吸附,获得良好的化学传感性能.玻璃态石墨烯器件探测丙酮的信噪比为48,比石墨烯器件提高了50%以上.此外,对偏压和厚度有关的挥发性有机化合物(VOC)感测功能的分析表明,少层玻璃态石墨烯更为敏感.这项研究表明玻璃态石墨烯在集成光电探测和化学传感多功能器件方面具有巨大应用前景.

Interface engineering of high performance all-inorganic perovskite solar cells via low-temperature processed TiO2 nanopillar arrays

All-inorganic perovskite solar cells suffer from low performance due to unsatisfactory carrier transport and light harvesting efficiency.Semiconductor nanopillar arrays can reduce light reflection loss and suppress exciton recombination dynamics in optoelectronic devices.In all-inorganic perovskite solar cells,few studies employing TiO_(2)nanopillar arrays(TiO_(2)NaPAs)have been reported to improve the device performance.Herein,well-arranged TiO_(2)NaPAs are chosen to enhance the interfacial contact between perovskite and electron transporting layers for improving the carrier transport.Notably,TiO_(2)NaPAs can be directly fabricated on rigid/flexible substrates at roughly room temperature by unique glancing angle deposition,which is more available than high-temperature hydrothermal/solvothermal methods.By embedding TiO_(2)NaPAs into chemical processable CsPbI2Br layers,continuous and intimate films are readily formed,guaranteeing large physical contact for facilitating more effective electron injection and charge separation.The vertically grown TiO_(2)NaPAs also provide a straightforward electron transporting path to electrodes.In addition,TiO_(2)NaPAs can guide the incident light and enhance the light-harvesting ability of CsPbI2Br films.As a result,the solar cell with TiO_(2)NaPAs displays a power conversion efficiency of 11.35%higher than planar control of 10.04%,and exhibits better long-term thermal stability.This strategy provides an opportunity by constructing direct interfacial regulation towards the performance improvement of inorganic perovskite solar cells.

Maillard reaction-derived laser lithography for printing functional inorganics

Photopolymerization-based additive printing of functional inorganics has drawn great attention in recent years and one important challenge is the photoresin loading with diverse inorganics. Here, we introduce a Maillard reaction-derived laser lithography strategy for an unprecedented direct printing of diverse inorganic compounds. The sugar-assisted laser lithography(SLL) is powerful to carry choice metal ions and versatile for the generation of patterned inorganic materials comprising metal oxides,metal sulfides, and metal nitrides, characterized by ferroelectric, magnetic, semiconductivity, superconductivity, or other properties. The material architecture is flexibly manipulated by the laser intensity, power, printing speed, precursor solution, and computer-aided design to satisfy the practical requirements. This work demonstrates a new possibility for the further development of laser lithography in the directly printing of feature-rich inorganic materials and devices.

Pressure Distinguishes the Dual Emissions in Pseudohalide 2D Ruddlesden-Popper Perovskite Cs_(2)Pb(SCN)_(2)Br_(2)

Two-dimensional(2D)Ruddlesden-Popper(RP)halide perovskites with diverse structures and properties have drawn increasing attention due to their promising optoelectronic applications.Recently,a new all-inorganic Cs_(2)Pb(SCN)_(2)Br_(2) has been reported that opens up new potential for the development of 2D RP perovskites.However,recent reports of unusual dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2) have generated intense debate about its origin and remains controversial.Here,by combining continuous pressure tuning with in situ diagnostics,we have unambiguously revealed the underlying mechanisms that the 2D Cs_(2)Pb(SCN)_(2)Br_(2) exhibits an intrinsic blue emission at 2.66 eV and an absorption edge close to the emission peak.While the gradually formed CsPbBr_(3) is responsible for the green emission at 2.33 eV with the absorption shoulder at 2.41 eV.Furthermore,by fitting the temperature-dependent intensity of the intrinsic blue emission,we have determined the corrected value of exciton binding energy for 2D Cs_(2)Pb(SCN)_(2)Br_(2) to be 90 meV.Intriguingly,an emission enhancement of 2.5 times is achieved in Cs_(2)Pb(SCN)_(2)Br_(2) under a mild pressure within 0.8 GPa,caused by the pressuresuppressed exciton-phonon interaction.This work not only elucidates the origin of the dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2),but it also provides a potential means to regulate and optimize the optoelectronic properties of 2D perovskites.