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By employing graphene quantum dots (GQDs), we have achieved a high efficiency of 16.55% in n-type Si heterojunction solar cells. The efficiency enhancement is based on the photon downconversion phenomenon of GQDs to make more photons absorbed in the depletion region for effective carrier separation, leading to the enhanced photovoltaic effect. The short circuit current and the fill factor are increased from 35.31 to 37.47 mA/cm(2) and 70.29% to 72.51%, respectively. The work demonstrated here holds the promise for incorporating graphene-based materials in commercially available solar devices for developing ultrahigh efficiency photovoltaic cells in the future.

Metal nanostructures with conical shape, vertical alignment, large ratio of cone height and curvature radius at the apex, controlled cone angle, and single-crystal structure are ideal candidates for enhancing field electron-emission efficiency with additional merits, such as good mechanical and thermal stability. However, fabrication of such nanostructures possessing all these features is challenging. Here, we report on the controlled fabrication of large scale, vertically aligned, and mechanically self-supported single-crystal Cu nanocones with controlled cone angle and enhanced field emission. The Cu nanocones were fabricated by ion-track templates in combination with electrochemical deposition. Their cone angle is controlled in the range from 0.3° to 6.2° by asymmetrically selective etching of the ion tracks and the minimum tip curvature diameter reaches down to 6 nm. The field emission measurements show that the turn-on electric field of the Cu nanocone field emitters can be as low as 1.9 V/μm at current density of 10 μA/cm(2) (a record low value for Cu nanostructures, to the best of our knowledge). The maximum field enhancement factor we measured was as large as 6068, indicating that the Cu nanocones are promising candidates for field emission applications.

Group-III-nitride semiconductors, including AlN, GaN, InN and their ternary, quaternary compounds, are promising electronic and optoelectronic materials for the applications in light emitting diodes, lasers, field emitters, photodetectors, artificial photosynthesis, and solar cells. Owing to their direct bandgaps ranging from near infra-red to deep ultraviolet. In recent years, the growth of group-III nitride nanostructures has been extensively explored. Herein, we provide a comprehensive review on the rational synthesis, fundamental properties and promising applications of group-III nitride nanostructures. Group-III nitride nanostructures with diverse morphologies, their corresponding synthesis methods and formation mechanisms involved are systematically compared and discussed, as well as the detailed factors that influence the optical and electrical properties of the nanostructures. The recent achievements gained in the fields of III-nitride nanostructures are highlighted, including light emitting diodes, laser diodes, photodetectors, solar cells, artificial photocatalysis, nanosensors, and nanogenerators. Finally, some perspectives and outlook on the future developments of III-nitride nanostructures are commented.

In the last decade, the research on two-dimensional (2D) materials has drawn a lot of interest from the aspects of both fundamental study and practical application. The atomic-scale thickness and unique layered structure make the materials in this family exhibit a number of distinct optical and electrical properties from their bulk counterparts. Previous studies have mainly focused on the crystalline 2D candidates. Recently, the highly disordered form of 2D materials, such as amorphous 2D materials, is emerging to attract increasing attention since it has shown great potential for applications in various fields. Here, we give a perspective on the recent progress in 2D amorphous inorganic materials. First, the synthesis techniques and process of 2D amorphous materials and their hybrid structure are given. Furthermore, the intriguing properties and applications in electronic, optoelectronic, and energy fields from typical 2D amorphous inorganic materials, including amorphous graphene, amorphous molybdenum disulfide, amorphous boron nitride, and amorphous black phosphorus, are introduced. Furthermore, the advantages and mechanisms of 2D amorphous materials are illustrated, pointing out the application scope of this material group. Finally, the underlying challenges of amorphous inorganic 2D materials are briefly outlined and some future outlooks are suggested.

Zinc sulfide (ZnS) quantum dots (QDs) were synthesized using a facile, low-cost and environmentally friendly method at room temperature and ambient pressure. The structural, optical and electrical properties of the as-prepared ZnS QDs were investigated. The monodispersed crystalline ZnS QDs with an average size of 3.8 nm has been prepared, an absorption peak at 292 nm in the ultra-violet (UV) range was observed. The maximum responsivity (R) and detectivity (D*) of the ZnS QDs based photodetector under 365 nm UV light illumination were 5.8 A W−1 and 1.97 × 1013 Jones, respectively, which shows important potential application in UV detection.

Two-dimensional (2D) metallic transition metal dichalcogenides (TMDs) exhibit fascinating quantum effects, such as charge-density-wave (CDW) and weak antilocalization (WAL) effect. Herein, low temperature synthesis of 1T phase VSe2 single crystals with thickness ranging from 3 to 41 nm by chemical vapor deposition (CVD) is reported. The VSe2 shows a decreasing phase transition temperature of the CDW when the thickness is decreased. Moreover, low-temperature magnetotransport measurements demonstrate a linear positive and non-saturating magnetoresistance (MR) of 35% from a 35 nm thick VSe2 at 15 T and 2 K due to CDW induce mobility fluctuations. Surprisingly, Kohler's rule analysis of the MR reveals the non-applicability of Kohler's rule for temperature above 50 K indicating that the MR behavior cannot be described in terms of semiclassical transport on a single Fermi surface with a single scattering time. Furthermore, WAL effect is observed in the 4.2 nm thick VSe2 at low magnetic fields at 2 K, revealing the contribution of the quantum interference effect at the 2D limit. The phase coherence length [Formula: see text] and spin-orbit scattering length [Formula: see text] were determined to be 73 nm and 18 nm at 2 K, respectively. Our work opens new avenues to study the fundamental quantum phenomena in CVD-deposited TMDs.

The fabrication of van der Waals heterostructures mainly extends to two-dimensional (2D) materials that are exfoliated from their bulk counterparts, which is greatly limited by high-volume manufacturing. Here, we demonstrate multilayered PtS

Discrete-scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity that can be rarely observed in quantum systems. Here, we report the log-periodic quantum oscillations in the longitudinal magnetoresistivity (ρxx) and the Hall traces (ρyx) of HfTe5 crystals, which reveal the DSI in the transport-coefficients matrix. The oscillations in ρxx and ρyx show the consistent logB-periodicity with a phase shift. The finding of the logB oscillations in the Hall resistance supports the physical mechanism as a general quantum effect originating from the resonant scattering. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. This work evidences the universality of the DSI in the Dirac materials and provides indispensable information for a full understanding of this novel phenomenon.

Palladium diselenide (PdSe2) films exhibit a high charge carrier mobility and sensitivity in photodetection. In this work, wafer-scale PdSe2 thin films with controllable thickness have been synthesized by the selenization of Pd films. A PdSe2-based photodetector can detect a broad wavelength ranging from 420 nm to 1200 nm. The responsivity and detectivity can reach 1.96 × 103 A W−1 and 1.72 × 1010 W Hz−1/2 at VSD = 3 V, respectively. The figure of merit of the photodetection are comparable to the mechanically exfoliated PdSe2 based photodetector. This work demonstrated that selenization is a facile method to synthesize PdSe2 films in large scale and the films are promising for broadband photodetection.

Graphene dots (GDs) are used for enhancing the performance of the poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)-based counter electrodes in Pt-free dye-sensitized solar cells (DSSCs). As compared to PEDOT:PSS CEs, GD–PEDOT:PSS films possess a rough surface morphology, high conductivity and electrocatalytic activity, and low charge-transfer resistance toward I − /I 3 − redox reaction, pushing cell efficiency to 7.36%, which is 43% higher than that of the cell with PEDOT:PSS CEs (5.14%). Without much impact on efficiency, the DSSCs with GD–PEDOT:PSS CEs work well under low-light conditions (light intensity −2 and angle of incidence >60°), such as indoor and low-level outdoor lighting and of the sun while the other traditional cells would fail to work. The concurrent advantage in low cost in Pt-free materials, simple fabrication processes, comparable efficiency with Pt CEs, and high performance under low-light conditions makes the DSSC with GD–PEDOT:PSS CEs suitable to harvest light for a diverse range of indoor and low-level outdoor lighting locations.

Black phosphorus (BP) is a very promising material for telecommunication due to its direct bandgap and strong resonant absorption in near-infrared wavelength range. However, ultrafast nonlinear photonic applications relying on the ultrafast photocarrier dynamics as well as optical nonlinearity in black phosphorus remain unexplored. In this work, nonlinear optical properties of solution exfoliated BP are investigated and the usage of BP as a new saturable absorber for high energy pulse generation in fiber laser is demonstrated. In order to avoid the oxidization and degradation, BP is encapsulated by polymer matrix which is optically transparent in the spectrum range of interest to form a composite. Two fabrication approaches are demonstrated to produce BP-polymer composite films which are further incorporated into fiber laser cavity as nonlinear media. BP shows very fast carrier dynamics and BP-polymer composite has a modulation depth of 10.6%. A highly stable Q-switched pulse generation is achieved and the single pulse energy of 194 nJ is demonstrated. The ease of handling of such black phosphorus-polymer composite thin films affords new opportunities for wider applications such as optical sensing, signal processing, and light modulation.

Amorphous black phosphorus (a-BP) ultrathin films are deposited by pulsed laser deposition. a-BP field-effect trans-istors, exhibiting high carrier mobility and moderate on/off current ratio, are demonstrated. Thickness dependence of the bandgap, mobility, and on/off ratio are observed. These results offer not only a new nanoscale member in the BP family, but also a new opportunity to develop nano-electronic devices.

We report a simple approach based on a chemical reduction method to synthesize aqueous inorganic ink com- prised of hexagonal MnO2 nanosheets. The MnO2 ink exhibits long-term stability and continuous thin films can be formed on various substrates without using any binder. To obtain a flexible electrode for capacitive energy storage, the MnO2 ink was printed onto commercially available A4 paper pretreated with multiwalled carbon nanotubes. The electrode exhibited a max- imum specific capacitance of 1035 F g � 1 (91.7 mF cm � 2 ). Paper- based symmetric and asymmetric capacitors were assembled, which gave a maximum specific energy density of 25.3 Wh kg � 1 and a power density of 81 kW kg � 1 . The device could maintain a 98.9 % capacitance retention over 10 000 cycles at 4 A g � 1 . The MnO2 ink could be a versatile candidate for large-scale production of flexible and printable electronic devices for energy storage and conversion.

Ag nanostructures are widely used in catalysis, energy conversion and chemical sensing. Morphology-tailored synthesis of Ag nanostructures is critical to tune physical and chemical properties. In this study, we develop a method for synthesizing the morphology-tailored Ag nanostructures in aqueous solution at a low temperature (45 °C). With the use of AgCl nanoparticles as the precursor, the growth kinetics of Ag nanostructures can be tuned with the pH value of solution and the concentration of Pd cubes which catalyze the reaction. Ascorbic acid and cetylpyridinium chloride are used as the mild reducing agent and capping agent in aqueous solution, respectively. High-yield Ag nanocubes, nanowires, right triangular bipyramids/cubes with twinned boundaries, and decahedra are successfully produced. Our method opens up a new environmentally-friendly and economical route to synthesize large-scale and morphology-tailored Ag nanostructures, which is significant to the controllable fabrication of Ag nanostructures and fundamental understanding of the growth kinetics.

To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size and thickness. Due to the edge and quantum confinement effect, WS2 quantum dots (2.35 nm) exhibit the lowest FON (0.01 J cm−2) and FOL (0.062 J cm−2) among all the samples, which are comparable to the lowest threshold achieved in graphene based materials, showing great potential as NOA materials with tunable properties.

Gallium selenide, an important second-order nonlinear semiconductor, has received much scientific interest. However, the nonlinear properties in its two-dimensional (2D) form are still unknown. A strong second harmonic generation (SHG) in bilayer and multilayer GaSe sheets is reported. This is also the first observation of SHG on 2D GaSe thin layers. The SHG of multilayer GaSe above five layers shows a quadratic dependence on the thickness; while that of a sheet thinner than five layers shows a cubic dependence. The discrepancy between the two SHG responses is attributed to the weakened stability of non-centrosymmetric GaSe in the atomically thin flakes where a layer-layer stacking order tends to favor centrosymmetric modification. Importantly, two-photon excited fluorescence has also been observed in the GaSe sheets. Our free-energy calculations based on first-principles methods support the observed nonlinear optical phenomena of the atomically thin layers.

Metals have the best dielectric screening capability among all materials; however, it is usually difficult to fabricate continuous and uniform ultrathin (few-atomic-layer thickness) metal films. Conversely, high-quality atomic-thick semiconductor or semimetal materials (so called two-dimensional materials) such as graphene or MoS

Although organic photovoltaic devices (OPVs) have been investigated for more than two decades, the power conversion efficiencies of OPVs are much lower than those of inorganic or perovskite solar cells. One effective approach to improve the efficiency of OPVs is to introduce additives to enhance light harvesting as well as charge transportation in the devices. Here, black phosphorus quantum dots (BPQDs) are introduced in OPVs as an additive. By adding 0.055 wt % BPQDs relative to the polymer donors in the OPVs, the device efficiencies can be dramatically improved for more than 10 %. The weight percentage is much lower than that of any other additive used in OPVs before, which is mainly due to the two-dimentional structure as well as the strong broadband light absorption and scattering of the BPQDs. This work paves a way for using two-dimentional quantum dots in OPVs as a cost-effective approach to enhance device efficiencies.

Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS2 nanosheets via solution processing is demonstrated. The results show that the collection of charge carriers is strongly dependent on the electronic properties of the 2D MoS2 with metallic MoS2 showing high responsivity and the semiconducting phase exhibiting high on/off ratios.

Herein, we report an effective and simple method for producing Tellurium Quantum dots (TeQDs), zero-dimensional nanomaterials with great prospects for biomedical applications. Their preparation is based on the ultrasonic exfoliation of Te powder dispersed in 1-methyl-2-pyrrolidone. Sonication causes the van der Waals forces between the structural hexagons of Te to break so that the relatively coarse powder breaks down into nanoscale particles. The TeQDs have an average size of about 4 nm. UV-Vis absorption spectra of the TeQDs showed an absorption peak at 288 nm. Photoluminescence excitation (PLE) and photoluminescence (PL) are used to study the optical properties of TeQDs. Both the PLE and PL peaks revealed a linear relationship against the emission and excitation energies, respectively. TeQDs have important potential applications in biological imaging and catalysis as well as optoelectronics.

Graphene quantum dot–polyaniline (PANI–GQD) composite films were synthesized by a chemical oxidation polymerization process. The optical properties of the PANI–GQD composite were studied by varying the mole concentration of PANI and the size of the GQDs. The Au/PANI–GQDs/ITO sandwich device was fabricated in order to investigate the transport properties of the composite. A stable hysteresis loop was observed in response to the applied voltage. By varying the PANI content and size of the GQDs, the area within the hysteresis loop and electrical conductance behavior of the device can be tuned in a controlled manner. Both the tunable luminescence and electrical hysteresis behavior are attributed to surface states of the GQDs. The PANI–GQD composite films are expected to find application in photonic devices.

A stretchable electronic device can retain its functionalities during high-level mechanical deformation, and stimulates the applications in the field of wearable and bio-implantable electronics. Efficient energy storage devices are an indispensable component in stretchable electronic systems. To integrate power supplies together with electronic devices that are mechanically flexible and stretchable, we demonstrate a new kind of stretchable all-solid-state supercapacitor, which consists of two slightly separated polyaniline/graphene electrodes in a wavy shape, with a phosphoric acid/polyvinyl alcohol gel as the solid-state electrolyte and separator. The as-fabricated wavy shaped supercapacitor was encapsulated in an elastomeric substrate which can be stretched to a large extent without mechanical degradation. The supercapacitor exhibited a maximum specific capacitance of 261 F g−1. Electrochemical cycling testing with the supercapacitor showed 89% capacitance retention over 1000 charge–discharge cycles at a current density of 1 mA cm−2. The bending and stretching tests showed that the supercapacitor maintained high mechanical strength and high capacitance simultaneously, even under a strain of 30%. This stretchable all-solid-state supercapacitor shows great potential as an energy storage device for stretchable electronic systems.

Graphene oxide (GO) was synthesized by a hydrothermal method using glucose solution as the sole reagent. The wavelength-dependent photoresponse of GO was investigated by fabricating metal–GO–metal photodetectors. The devices demonstrated a broadband photoresponse from 290 to 1610 nm covering deep ultraviolet (UV) to near-infrared (NIR), which is the broadest spectral range yet demonstrated on GO. The response times of the photodetectors in the UV and visible range are about 100 ms, which are at least one order of magnitude faster than photodetectors based solely on GO reported previously. The responsivity of the photodetector can be as high as 23.6 mA W−1 in the visible range. The wavelength-dependent photoresponse is closely related to the absorption characteristics of GO. Potential for a self-powered GO based photodetector is first demonstrated, and the device shows a prominent photoresponse at zero bias. The GO based photodetectors pave the way for developing low-cost, broadband, self-powered as well as spectrally tuneable photodetectors.

Ferroelectric domain walls exhibit a number of new functionalities that are not present in their host material. One of these functional characteristics is electrical conductivity that may lead to future device applications. Although progress has been made, the intrinsic conductivity of BiFeO3 domain walls is still elusive. Here, the intrinsic conductivity of 71° and 109° domain walls is reported by probing the local conductance over a cross section of the BiFeO3 /TbScO3 (001) heterostructure. Through a combination of conductive atomic force microscopy, high-resolution electron energy loss spectroscopy, and phase-field simulations, it is found that the 71° domain wall has an inherently charged nature, while the 109° domain wall is close to neutral. Hence, the intrinsic conductivity of the 71° domain walls is an order of magnitude larger than that of the 109° domain walls associated with bound-charge-induced bandgap lowering. Furthermore, the interaction of adjacent 71° domain walls and domain wall curvature leads to a variation of the charge distribution inside the walls, and causes a discontinuity of potential in the [110]p direction, which results in an alternative conductivity of the neighboring 71° domain walls, and a low conductivity of the 71° domain walls when measurement is taken from the film top surface.

Tin sulfide quantum dots (SnS2 QDs) are n-type wide band gap semiconductor. They exhibit a high optical absorption coefficient and strong photoconductive property in the ultraviolet and visible regions. Therefore, they have been found to have many potential applications, such as gas sensors, resistors, photodetectors, photocatalysts, and solar cells. However, the existing preparation methods for SnS2 QDs are complicated and require a high temperature and high pressure environments; hence they are unsuitable for large-scale industrial production. An effective method for the preparation of monodispersed SnS2 QDs at normal temperature and pressure will be discussed in this paper. The method is facile, green, and low-cost. In this work, the structure, morphology, optical, electrical, and photoelectric properties of SnS2 QDs are studied. The synthesized SnS2 QDs are homogeneous in size and exhibit good photoelectric performance. A photoelectric detector based on the SnS2 QDs is fabricated and its J–V and C–V characteristics are also studied. The detector responds under λ = 365 nm light irradiation and reverse bias voltage. Its detectivity approximately stabilizes at 1011 Jones at room temperature. These results show the possible use of SnS2 QDs in photodetectors.

Solid-state graphene oxide (GO) homogeneously incorporated silica gel glasses have been successfully fabricated, and the good nonlinear optical (NLO) response shown indicates its high potential as the optical limiting material to protect optical detectors and human eyes from damage caused by high power lasers. The GO sheets are covalently functionalized with 3-aminopropyltriethoxysilane and connected to the silica glass matrix through Si–O bonding, resulting in an increase in GO incorporation concentration up to 20.2 mol % (C/SiO2) without reaching the saturation limit. Digital images and element mapping analysis of carbon have confirmed the homogeneous dispersion of GO in the silica gel glass. Because of the higher two-photon absorption coefficient, lower NLO starting threshold, and optical limiting threshold shown at 532 nm wavelength, the NLO performance at this wavelength is better than at 1064 nm. At an input fluence as low as 1.3 J cm–2 at 532 nm and 2.3 J cm–2 at 1064 nm, the glass incorporated wit...

We present theoretical and experimental investigations on the growth of SnS van der Waals epitaxies (vdWEs) on graphene buffer layer (GBL). Local density approximation (LDA) was used to evaluate the bond length disorder, binding energies, and growth orientations for SnS deposited on crystalline semiconductor substrates with and without the GBL. Strong bond length disorder is observed for SnS deposited directly on GaAs substrates, whereas in the case where a GBL is used the disorder is substantially reduced. First-principle calculations indicate two favored growth orientations for SnS deposited on GBL resulting in 12 distinct peaks in the azimuthal hard X-ray diffraction (HXRD) scan due to the structural symmetry of the GBL. The results stipulate formation of strong chemical bonds at the GaAs/SnS interface while the interaction between SnS and the underlying GBL is dominated by vdW force. Nevertheless this vdW force is shown to be strong enough to induce favored nucleation orientations for the SnS and is e...

Single-layer graphene was transferred onto (1 – x)[Pb(Mg1/3Nb2/3)O3]–x[PbTiO3]0.3 (PMN-PT) substrate to investigate the transport properties of graphene-based field effect transistors (FETs) by ferroelectric gating. The graphene/PMN-PT FET exhibited p-type characteristics with a large memory window and an on/off current ratio of about 5.5 in air ambient conditions at room temperature. By prepoling the PMN-PT substrate, the FET showed a reduction in p-doping for the graphene/PMN-PT FET, implying the pre-polarization and the polarization reversal played an important part in the behaviors of graphene on PMN-PT. The observation of simultaneous rise in gate current with the dramatic transition in drain current suggested that the transport properties of graphene mainly stemmed from the coupling of the ferroelectric polarization to the charge carriers in graphene. The field effect mobility and the excess hole concentration were calculated to be about 4.52 × 103 cm2 V–1 s–1 and 6.74 × 1012 cm–2, respectively. Fur...

This paper describes a selective control of the flow direction in microfluidic chips using a laser induced thermal bubble. The bubble is generated inside the microchannel by focusing a continuous-wave laser onto the tear-drop shaped metal pad underneath the microchannel. Experiments demonstrate that the unidirectionally growing bubble acts as an in-channel directional micro-pump and can drive the flow to a freely chosen direction at a T-junction by pumping at different locations. In addition, the pumping flow rate could be adjusted in the real time and this technology is applicable to many types of common liquids. These advantages make it useful for flexible microfluidic manipulation in lab-on-a-chip systems and microchannel networks.

Mechanical exfoliation from bulk layered crystal is widely used for preparing two-dimensional (2D) layered materials, which involves not only out-of-plane interlayer cleavage but also in-plane fracture. Through a statistical analysis on the exfoliated 2D flakes, we reveal the in-plane cleavage behaviors of six representative layered materials, including graphene, h-BN, 2H phase MoS2, 1T phase PtS2, FePS3, and black phosphorus. In addition to the well-known interlayer cleavage, these 2D layered materials show a distinctive tendency to fracture along certain in-plane crystallography orientations. With theoretical modeling and analysis, these distinct in-plane cleavage behaviors can be understood as a result of the competition between the release of the elastic energy and the increase of the surface energy during the fracture process. More importantly, these in-plane cleavage behaviors provide a fast and noninvasive method using optical microscopy to identify the lattice direction of mechanical exfoliated 2D layered materials.

The electrical and optical measurements, in combination with density functional theory calculations, show distinct layer-dependent semiconductor-to-semimetal evolution of 2D layered PtSe

Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS

A 2D system of Er-doped MoS2 layered nanosheets is developed. Structural studies indicate that the Er atoms can be substitutionally introduced into MoS2 to form stable doping. Density functional theory calculation implies that the system remains stable. Both NIR-to-NIR up-conversion and down-conversion light-emissions are observed in 2D transition metal dichalcogenides, ascribed to the energy transition from Er(3+) dopants.

The two-dimensional layered semiconducting tungsten disulfide (WS2) film exhibits great promising prospects in the photoelectrical applications because of its unique photoelectrical conversion property. Herein, in this paper, we report the simple and scalable fabrication of homogeneous, large-size and transferable WS2 films with tens-of-nanometers thickness through magnetron sputtering and post annealing process. The produced WS2 films with low resistance (4.2 kΩ) are used to fabricate broadband sensitive photodetectors in the ultraviolet to visible region. The photodetectors exhibit excellent photoresponse properties, with a high responsivity of 53.3 A/W and a high detectivity of 1.22 × 1011 Jones at 365 nm. The strategy reported paves new way towards the large scale growth of transferable high quality, uniform WS2 films for various important applications including high performance photodetectors, solar cell, photoelectrochemical cell and so on.

12 ] Therefore, graphene-based IR detectors have much lower responsivities than photoconductors based on QDs. It is reasonable to consider that the responsivity of a graphene-based IR detector can be improved substantially by modifying the graphene fi lm with QDs, which can absorb IR light more effi ciently. On the other hand, if the carriers gener-ated by IR light can transfer to the graphene fi lm, their mobility will be much higher and thus the responsivity will be dramati-cally improved for a QD-based IR detector. Moreover, an array of graphene devices can be easily patterned by state-of-the-art techniques and this could possibly lead to elimination of the crosstalk between neighboring pixels that occur in silicon devices.

Carbon-doped ZnO (ZnO:C) nanoneedles were fabricated using ion beam irradiation with a simultaneous supply of carbon at room temperature. The structure and the magnetic properties of the ZnO:C nanoneedles were investigated. Hysteresis loops and zero-field cooling (ZFC) and field cooling (FC) curves demonstrated the ferromagnetic properties of the ZnO:C nanoneedles. The Curie temperature of the ZnO:C is above 330 K. The ferromagnetic anisotropy with an easy axis perpendicular to the shape axis of the ZnO:C nanoneedles was observed due to the dipole–dipole magnetic interaction amongst nanoneedles.

By employing graphene quantum dots (GQDs) in PEDOT:PSS, we have achieved an efficiency of 13.22% in Si/PEDOT:PSS hybrid solar cells. The efficiency enhancement is based on concurrent improvement in optical and electrical properties by the photon downconversion process and the improved conductivity of PEDOT:PSS via appropriate incorporation of GQDs. After introducing GQDs into PEDOT:PSS, the short circuit current and the fill factor of rear-contact optimized hybrid cells are increased from 32.11 to 36.26 mA/cm2 and 62.85% to 63.87%, respectively. The organic–inorganic hybrid solar cell obtained herein holds the promise for developing photon-managing, low-cost, and highly efficient photovoltaic devices.

We report a nonlithographic fabrication method to grow uniform and large-scale crystalline silicon (Si) nanodot (c-SiNDs) arrays on single-layer graphene by an ultrathin anodic porous alumina template and Ni-induced Si crystallization technique. The lateral height of the template can be as thin as 160 nm and the crystallization of Si can be achieved at a low temperature of 400 °C. The effects of c-SiNDs on graphene were studied by Raman spectroscopy. Furthermore, the c-SiNDs/graphene based field effect transistors were demonstrated.

Metallo-dielectric photonic crystals (MDPCs) are used as ultrasensitive molecular detectors for concentrations down to picomolar level based on surface-enhanced Raman spectroscopy (SERS). Calculations show that the amorphous silicon photonic crystals (a-Si PCs) embedded in multiple metallo-dielectric (MD) units can significantly increase the electromagnetic fields at the air-dielectric interface, leading to remarkable Raman enhancement. Corresponding experiments show the multiple MDPC structures can serve as an ultrasensitive SERS substrate with excellent reproducibility and stability, capable of quantitative analysis down to 10 pM level. The MDPC structure can be generalized to other applications, such as plasmonic devices, ultrasensitive sensors, and nanophotonic systems.