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[Display omitted] • Self-powered MoS 2 /Si flexible photodetectors with Al 2 O 3 interface were developed. • The vertical MoS 2 nanofilms were grown by RF magnetron sputtering and Al 2 O 3 by ALD. • The photodetectors could be bent up to 120° and worked well after 200 bending times. • R of 0.047 A/W and D* of 5.67 × 1011 Jones were obtained under 980 nm with 200 μW/cm2. The self-driven flexible photodetector is vitally important for next-generation optoelectronics. Two-dimensional (2D) molybdenum sulfide (MoS 2) as a typical family member of transition-metal dichalcogenides (TMDs) has shown larger potential applications in the high-sensitivity photodetection due to its self-physical properties. Herein, the ultrafast MoS 2 /Si flexible photodetector with ultrathin Al 2 O 3 passivation interface and high light-trapping structures was fabricated. The MoS 2 /Al 2 O 3 /Si flexible photodetector exhibits excellent performance with a high responsivity of 0.047 A/W, detectivity up to 5.67 × 1011 Jones and rise/fall time of 25.6/3.2 μs. Furthermore, this optoelectronic device can withstand bending angles of 120° and work well after 500 bending times. This unique performance can be attributed to the flexible Si substrate with good mechanical properties, high-light trapping structures and an Al 2 O 3 passivation interface. This device can find potential applications in e-skins, flexible displays and smart health care. [ABSTRACT FROM AUTHOR]

Since challenges still exist in size control fabrication of inverted pyramids (IPs) on c -Si substrate, size difference of IPs among reported literatures still can not be explained reasonably. Here, formation mechanism of IPs from sub-micro scale to micro scale for light trapping on c -Si substrate is reported based on metal assisted chemical etching (MACE) temperature control for the first time. The formation of the IPs is realized through a mask-less Ag assisted wet chemical etching method followed by a post nanostructure rebuilding (NSR) process. It is found that the etching directions on (1 0 0) Si can be influenced by the MACE temperature due to the shrink of Ag nanoparticles at high MACE temperature, leaving behind few pore channels in the deepest region of black silicon layer as nucleation sites. Thus large IPs can be formed during the following NSR process. It is believed that the elucidation of the fundamental formation will speed up the fabrication of wafer-scale c -Si IPs for application in bulk and ultrathin c -Si solar cells. [ABSTRACT FROM AUTHOR]

To investigate the effects of Sb doping on the structural and electrical properties of Cu(InGa)Se 2 (CIGS) thin films and solar cells, CIGS thin films, prepared by e-beam evaporation on soda-lime glass, were doped with lower and upper Sb layers in the precursor stacks respectively. Change of structure and introduction of stress were observed in the CIGS thin films with upper Sb layer in stack through XRD and Raman measurement. Both crystalline quality and compactness of CIGS thin films were improved by the doping of upper Sb layer in stack and the CIGS thin film showed an optimal structural property with 20 nm Sb layer. Movement of Fermi level of the surface of CIGS thin film after doping of upper Sb layer in stack and electrons transfer between Cu/Cu + redox couple and CIGS thin films, which provided probability for the substitution of Sb for Cu sites at the surface of CIGS thin films, were proposed to explain the migration of Cu from the surface to the bulk of CIGS thin films. The larger barrier at the CIGS/CdS interface after doping of upper Sb layer in stack made contribution to the increase of V OC of CIGS solar cells. The efficiency of CIGS solar cell was improved from 3.3% to 7.2% after doping with 20 nm upper Sb. Compared to the CIGS solar cell with lower Sb layer in stack, in which an additional Cu 2-x Se phase was found, the CIGS solar cell with upper Sb layer in stack possessed a higher efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel electrolyte formula and co-electrodeposition parameters are presented. [•] The CZTS films are prepared from co-electrodeposited precursors. [•] CZTS film forms by reaction among binary and ternary sulfides at high temperature. [•] Photoluminescence was obtained from prepared CZTS films at 550°C for 1h. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fe(NO3)3/HF mixed solution was used to produce low reflective texture on mc-Si. [•] A microstructure having hemispherical etched pits with needle-like folds was obtained. [•] Etching time and the concentration of Fe(NO3)3 have key effects on the reflectivity. [•] A lowest reflectivity of 6.15% in the wavelength range of 400–1000nm was achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of the sulfurization temperature on the optoelectronic properties of CZTS film was researched. [•] Environmental friendly CZTS/i-a-Si/n-a-Si was firstly introduced and successfully prepared. [•] The photovoltaic performance of CZTS/i-a-Si/n-a-Si and CZTS/n-a-Si was firstly compared. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, pyramid-structured silicon wafers were etched in a reactive ion etching system at room temperature and without any negative voltage pulses to obtain antireflective nanostructures. The effects of the etching time, etching power and the flow ratio of the SF6 and O2 (FSF6/FO2) on the morphologies and reflective properties of the etched samples were studied. Scanning electron microscope was used to investigate the morphologies of etched samples. The surface reflectance measurements were carried out using UV–vis-NIR spectrophotometer. A reflectance of 4.72% from the etched surface in the wavelength range of 400–800nm was obtained under etching time of 20min, etching power of 150W and FSF6/FO2 of 18sccm/6sccm. Meanwhile, samples etched with FO2 lower than 6sccm can’t get low reflective silicon structure. Besides, the results show that overlong etching time of 30min and too big etching power of 225W would make the nanostructures too sparse to obtain a low reflectance. [Copyright &y& Elsevier]

Abstract: Cu2ZnSnS4 (CZTS) film was obtained by sulfurizing (Cu, Sn)S/ZnS structured precursor that was prepared by a combination of the successive ionic layer adsorption and reaction method and the chemical bath deposition method. Pure Cu2ZnSnS4 phase was obtained when the precursor was annealed at 500°C for 2h. The structure, composition, morphology and optical properties of the CZTS film were studied. The results show that the CZTS film has a relatively compact morphology, and the composition of the film is close to the stoichiometric ratio of Cu2ZnSnS4. The film presents a large optical absorption coefficient (larger than 104 cm−1 when the photo energy is beyond 1.47eV). The optical band-gap of the film is around 1.56eV. This method is considered a potential way to prepare high quality CZTS film. [Copyright &y& Elsevier]

Abstract: Porous-pyramids structured silicon surface was prepared and its influence on the reflectance of the silicon surface was studied. The porous-pyramids structured surface was prepared by electrochemical etching in HF/C2H5OH solution after texturization in NaOH/IPA solution. The average reflectance of the surface in the range of 400–800nm was as low as 1.9%. The optical photographs and SEM images of the surfaces prepared under optimized condition were investigated. The porous-pyramids structured surface has a gradient-index multilayer structure (i.e., the refraction index of the structure increase from the top to the bottom). A formula that describes the relationship between the reflectance and the index of refraction was used to explain the excellent broadband antireflection of the multilayer silicon surface. The technique of this paper may be valuable in the texturization process for high-efficiency silicon solar cells. [Copyright &y& Elsevier]

Abstract: In this work, hydrogenated amorphous silicon carbide (α-Si1−x C x :H) and nanocrystalline SiC (nc-SiC) thin films were deposited by hot wire CVD (HWCVD) using SiH4/C2H2/H2 gas mixtures. It was found that the films prepared under low gas pressure were α-Si1−x C x :H and those prepared under high gas pressure were nc-3C-SiC. The α-Si1−x C x :H films showed enhanced density of C–H n and Si–C bonds with increasing C2H2 fraction, which induced an increase in optical gap from 1.8 to 3.0eV. For the deposition process of nc-SiC, the E gopt of the deposited films varied from 1.9eV to 2.5eV as the filament temperature increased from 1700 to 2100°C. The deposition rate decreased rapidly from 5.74nm/min to 0.8nm/min with increasing T F . [Copyright &y& Elsevier]

Abstract: Nanowall shaped Bi2S3 films were prepared by chemical bath deposition in which ammonium citrate and thioacetamide were used as chelating reagent and sulfur source, respectively. The nanowall Bi2S3 films show large-surface-area nanowall shaped morphology. It is found that the pH value (pH=6 or pH=6.5) of the solution is a crucial parameter to obtain the nanowall shaped Bi2S3 films. The composition of the nanowall Bi2S3 films is close to the stoichiometric ratio of Bi2S3. The absorption edge of the nanowall shaped Bi2S3 films is located at around 900nm, indicating that the optical bandgap of the Bi2S3 films is around 1.4eV. The nanowall Bi2S3 films show obvious photo-sensitivity. The photo-to-dark conductivity ratios of the nanowall Bi2S3 films prepared at pH=6 and pH=6.5 are all around 50. This value is around five times than that of the non-nanowall shaped Bi2S3 films which is prepared at pH=7. [Copyright &y& Elsevier]

Abstract: Bismuth sulfide (Bi2S3) films were chemically deposited by a novel deposition system in which ammonium citrate was used as the chelating reagent. Two sulfur source thioacetamide (TA) and sodium thiosulfate (Na2S2O3) were used to prepare Bi2S3 films. Both the as-prepared films have amorphous structure. However, annealing can improve the crystallization of the films. The composition of the films prepared by TA and Na2S2O3 are all deviate from the stoichiometric ratio of Bi2S3. The Bi2S3 films are all homogeneous and well adhered to the substrate. The optical properties of the Bi2S3 films are studied. The electrical resistivity of the as-prepared films are all around 7×103 Ωcm in dark, which decreases to around 1×103 Ωcm under 100mW/cm2 tungsten–halogen illumination. After the annealing, the dark resistivity of the Bi2S3 film prepared by TA decreases by four magnitudes. In contrast, the dark resistivity of the Bi2S3 film prepared by Na2S2O3 only decreases slightly. [Copyright &y& Elsevier]

Abstract: SnS (stannous sulfide) films were prepared by chemical bath deposition in which a novel chelating reagent ammonium citrate was used. The film has a zinc blende structure or an orthorhombic structure which is determined by the pH value and the temperature of the deposition solution. The reason for this result is considered to be that SnS films prepared under different conditions have different deposition mechanisms (ion-by-ion mechanism for the zinc blende structured SnS and hydroxide cluster mechanism for the orthorhombic structured SnS). The prepared SnS films are homogeneous and well adhered. SEM images show that the SnS films with different structures have different surface morphologies. Electrical test shows that the resistivity of the films is as low as 420Ωcm and 3300Ωcm for orthorhombic and zinc blende SnS films, respectively, which are much lower than the ever reported values. Persistent photoconductivity (PPC) phenomena are observed for both the films with zinc blende and orthorhombic structures by photo-current responses measurement. The optical bandgaps of the SnS films are determined to be 1.75eV and 1.15eV for zinc blende structure and orthorhombic structure, respectively. [Copyright &y& Elsevier]

Abstract: SnS films have been prepared by a novel two-stage process. It involved sputtering of Sn film on glass substrate and sulfurization of the thin metallic tin precursor layers in a vacuum furnace. The X-ray diffraction results showed that the SnS layers had orthorhombic structure and (040) preferential growth is more and more obvious with the increase of sulfurization time. The SnS film obtained by this work shows high optical absorption efficiency, and the film has a direct optical band gap of about 1.3eV. The films show p-type conductivity and the resistivity of SnS film decreased obviously under illumination. [Copyright &y& Elsevier]

Abstract: Nanostructured Bi2S3 films that comprise rod-shaped particles were prepared on glass substrates by chemical bath deposition. When a SnS buffer layer was deposited on the substrate before the deposition of the Bi2S3 films, the homogeneity and the adhesion of the prepared Bi2S3 films are largely improved. Furthermore, when the buffer layer is inserted, the electrical conductivity of the films increases from lower than 10−6 Ω−1 cm−1 to 4×10−5 Ω−1 cm−1, and the average optical absorption in the band between 350nm and 800nm increases from around 41% to around 76%. The reason for these results is considered to be that the SnS layer can promote the nucleation of the Bi2S3 on the substrate. [ABSTRACT FROM AUTHOR]

• A combined strategy of preparing SiO x /MgO/Mg 2 SiO 4 /C was proposed. • The hierarchical microspheres were beneficial to cycling stability. • The initial coulombic efficiency of the SiO x -based anode material got improved. • Superb cycling stability and rate capability were achieved by introducing MgO. Silicon suboxide (SiO x) is considered as one of the potential candidates for next-generation lithium-ion battery (LIB) anode materials. However, the application of this material is limited by volume change during the discharging and charging process and its low initial cycle Coulombic efficiency (ICE). Herein, we report a controllable and cost-effective route to synthesize the SiO x /MgO/Mg 2 SiO 4 /C (SMC) composite using magesiothermic reaction (MTR), hot-water treatment, and carbonization process. Moreover, the composite exhibits a hierarchical buffer structure composed of microspheres. Because of its special dehydration ability to disrupt the hydrolytic cycle, the introduction of MgO is proved to be beneficial to LIBs' cycling performance and rate capability. Besides, with the formation of Mg 2 SiO 4 , the consumption of SiO 2 improves the ICE of the SMC anode to 87.48%. The hierarchical microstructure makes the resultant SMC anode exhibit a stable reversible capacity of 550 mAh g−1, which means a high capacity retention ratio of 78.81% after 200 cycles. Furthermore, the specific capacity of SMC anode keeps around 600 mAh g−1 at the current density of 800 mA g−1, showing superb rate performance. This work provides a novel approach to taking advantage of by-products of MTR and also demonstrates the potential of industrial application of SiO x /C anodes. [ABSTRACT FROM AUTHOR]

• A novel TiO 2 -CZTS heterostructure nanocomposite is designed and synthesized. • Photoreduction of CO 2 over TiO 2 -CZTS is conducted in CO 2 + H 2 O vapor. • TiO 2 -CZTS shows strong absorption in whole visible light region. • CZTS decorated TiO 2 synergistically enhances CO 2 reduction rate. • A possible photocatalytic mechanism of CO 2 reduction is proposed. Owing to human activities and intensive utilization of modern technology, the CO 2 concentration in the environment increases which concomitantly leads to global warming. In order to overcome this issue, photocatalytic reduction of CO 2 aims to develop new cost-effective catalytic chemistries with the ability to efficiently utilize the CO 2 and convert into sustainable alternative feedstock for commercial commodity chemicals. In this context, a series of TiO 2 -Cu 2 ZnSnS 4 nanocomposites are directly prepared by one-step hydrothermal method. The nanocomposites are intensively characterized as photocatalysts for photoreduction of CO 2 to gaseous hydrocarbons (CO and CH 4), under visible-light illumination. In comparison to TiO 2 for one hour of irradiation, the maximum generation-rates of CO and CH 4 over nanocomposite are 33 and 6 times as high, respectively. Excellent stability with almost similar generation-rate after 4 cycles shows that heterostructure nanocomposites may offer a potential approach to stimulate the efficiency of hybrid materials in photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

• Cd-free CIGS solar cells with a-Si buffer layers are fabricated for the first time. • The conduction band alignment of CIGS/a-Si is a favorable spike. • SCAPS predicts enhanced efficiency by optimization of bandgap and E CB of CIGS films. • The efficiency of cell with modified CIGS film is relatively improved by over 30%. CdS, In 2 S 3 and ZnO-based materials are typically adopted as buffer layers in high efficiency CIGS solar cells. However, the drawbacks involved toxicity, complicated synthesis process and environmental damage of aforementioned materials would someday limit the development themselves. Here, for the first time, eco-friendly and low-cost a-Si thin films prepared by e-beam evaporation were used as buffer layers in CIGS solar cells. Thickness of a-Si films was changed to optimize the performance of CIGS solar cells through investigating their optical, structural and electrical properties. It revealed that the conduction band alignment of CIGS and a-Si is a favorable spike and a 60 nm a-Si film is optimal for CIGS/a-Si interface properties. Following the SCAPS simulation, bandgaps and conduction band energy level of CIGS films were facilely modulated through altering the Ga/(Ga + In) ratios. The conversion efficiency of solar cell with modified CIGS film was relatively improved by over 30% compared to the pristine one. The present work provides a new and eco-friendly strategy for fabrication of CIGS solar cells and expands the application of a-Si thin films as buffer layers for solar cells. [ABSTRACT FROM AUTHOR]

• In-situ facile synthesis of mesoporous TiO 2 -CZTS nanocomposite as photocatalyst. • Significantly improved visible-light absorption by mesoporous structure of the catalyst. • Highly enhanced degradation reaction with TiO 2 -CZTS nanocomposite. • Studying critical role of superoxide and hydroxyl radicals in degradation. In this study, a n-p type mesoporous TiO 2 -Cu 2 ZnSnS 4 heterostructured photocatalyst was synthesized by single-step in situ hydrothermal route and characterized by XRD, Raman, SEM, HRTEM, FT-IR, BET, DRS and XPS. The results show that the introduction of CZTS extends the light absorption of TiO 2 into visible region, which led to increase in physically absorbed oxygen and surface hydroxyl group and subsequently diminished the recombination rate of photo-generated charge carriers. The photocatalytic activity of nanocomposites was investigated by degradation of rhodamine B (RhB) and methyl orange (MO) under the visible-light irradiation. The visible-light driven photo-degradation improved remarkably with TiO 2 -CZTS as photocatalyst and no significant change in crystalline phase and surface morphology of heterostructured nanocomposite was observed. Furthermore, the results confirm that the photo-degradation by TiO 2 -CZTS photocatalyst obey the first order kinetics with apparent rate constant (k app) of 0.0551 min−1 (RhB) and 0.01733 min−1 (MO) with the half time period (t 1/2) of 12.48 min and 39.99 min, respectively, and propose that the p-n type TiO 2 -CZTS heterostructured photocatalyst could emerge as a promising candidate for environmental remediation applications. [ABSTRACT FROM AUTHOR]

• Size control of IPs from sub-micro to micro scale was achieved by varying ρ values. • 40 µm random INPs cell achieved 34.8 mA/cm2 current density and 17.44% efficiency. • Superior mechanical performance was proved on INPs based 40 µm c -Si. • Quasi-omnidirectional characteristics of INPs was found between 0° and 60°. • Quasi-omnidirectional performance of INPs was demonstrated by FDTD simulation. Flexible ultrathin c -Si (U-Si) solar cell is widely researched for its potential usage in places with various shapes and sizes. However, light incident angle (θ) varies with positions on the same cell accompanied with the easy crack of cell due to surface textures when the U-Si cell is under bending. Therefore, the fabrication of efficient antireflectance structures with both quasi-omnidirectional performance and superior mechanical performance is greatly required. Here, size control of inverted pyramid (IP) from nano to micro scale as antireflectance structures is realized by altering ρ ([HF]/[HF] + [H 2 O 2 ]) values at room temperature. The IP is obtained through the nanostructure rebuilding (NSR) treatment of Ag assisted chemical etched nanostructures. In comprehensive consideration of optical and mechanical performances, IP-60 (ρ = 60%) textured 40 µm U-Si cell is successfully fabricated with a short-current density of 34.8 mA/cm2 and energy-conversion efficiency of 17.44%, showing an 0.2 mA/cm2 and 0.13% improvement respectively compared with that of the micro pyramids (MP) based one. Moreover, the quasi-omnidirectional characteristics of IP-60 based 40 μm cell over 0–60° is demonstrated by experiment and simulation. The above finding makes it possible to broaden the application scope of U-Si cells into some new areas like stratospheric airships and wearable electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous SiO X was controllably produced by adding NaCl in the magnesiothermic process. • Increase of NaCl content produced O-rich SiO X @C with the high specific surface area. • 3D network of SiO X @C promoted fast diffusion of lithium-ion. • Graphite-like carbon coatings improved the electronic conductivity of SiO X @C. • Porous SiO X @C with rich oxygen led to superior electrochemical properties of LIB. Silicon suboxide (SiO X) is a promising anode material for lithium ion battery (LIB). However, oxygen-dependent SiO X poses a great impact on its cycling stability, which is difficult to controllably prepare. Additionally, the aggregation of nano-scale SiO X restricts the diffusion of lithium ion and structural stability during cycles. Herein, we realize the controllable preparation of porous SiO X /C sheets with various oxygen content and graphite-like carbon as anode materials of LIB. It is found that high oxygen content and a 3-dimensional network in SiO X /C can ensure high structural stability during cycles. As-prepared SiO X facilitates the growth of graphite-like carbon with high defect density, improving their electron and ion conductivity. As-prepared SiO X @C sheets deliver superior reversible capacity, cycling stability and rate performance (the second discharging capacity of 717.4 mAh g−1 at 100 mA g−1 with high initial Coulombic Efficiency of 64.08% is obtained; its capacity retention is as high as 100.44% against the second discharging capacity after 200 cycles; at a high current density of 2000 mA g−1, its reversible capacity still remains 389 mAh g−1). This work provides a novel and simple approach to controllably prepare disproportionated SiO X @C sheets with the 3-dimensional network as ultrastable SiO x -based anode materials of LIB for practical application. [ABSTRACT FROM AUTHOR]