CuS Films Research Articles

Effect of reduction potential and post-deposition annealing on the structural, compositional and optical properties of electrodeposited copper(I) sulfide thin films

In the present work it is reported on the deposition of cuprous sulfide (Cu2S) by the electrodeposition technique and its characterization followed by a heat treatment. Cu2S films were deposited using reduction potentials in a range of − 600 to − 555 mV (vs. SCE) with a deposition time of 1000 s. The annealing process was performed varying the atmosphere (inert or with sulfur) and temperature (250 and 350 °C). The properties of deposited Cu2S films were analyzed using UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The deposited films had a hexagonal structure in the chalcocite phase and showed a band gap in the range of 1.61 and 1.8 eV. Characterization techniques demonstrated modifications in the properties of the material due to the presence or deficiency of sulfur in the films.

Investigation of the usage possibility of CuO and CuS thin films produced by successive ionic layer adsorption and reaction (SILAR) as solid lubricant

CuO and CuS films were coated on AISI 4140 steel samples by Successive Ionic Layer Adsorption and Reaction (SILAR) to investigate their usability as solid lubricant. Wear tests were performed using pin-on-disk tribo-tester under dry and lubricated conditions. The structural, morphological and morphological features of untreated, CuO and CuS coated samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and microhardness, scratch analysis. The surface examinations indicated that needle-like structures formed after coating processes and CuO and CuS films exhibited oleophobic behavior. CuO and CuS thin films reduced the coefficient of friction due to the low shear strength of bonding in transfer films. CuO and CuS films decreased the wear rates in comparison to untreated sample for both dry and lubricated conditions. Also, CuO thin films exhibited better wear resistance than CuS films in dry and lubricated wear tests. The overall results revealed that both CuO and CuS films produced by SILAR can be an alternative to conventional solid lubricants.

Electrical properties of grain size tuned CdSe nanocrystal films for practical applications

CdSe nanocrystal (NC) thin films of different NC sizes were synthesized using vacuum deposition technique. The films showed blue shift of band gap and the NC sizes calculated size using Brus equation were 9.40, 9.68 and 9.82nm. DC conductivity and photoconductivity of as-deposited and annealed films increased and activation energy for conduction decreased with increase in the NC size. Also, both carrier concentration and mobility of the films increased with increase in the size of the NCs which was attributed to the increased electronic coupling between the NCs. The slow response part of photocurrent response pulse analyzed using power law: Iph ∞ tα gave larger values for α for larger NC size indicating stronger electronic coupling between grains in films of larger grain sizes. Charge transport in the CdSe NC films was akin to that of solid films of CdSe quantum dots, of sizes given by Brus equation, connected together by an outer shell of CdSe material where charge carriers had free movement. Additionally, measurement of the characteristics of the hetero-junction formed by the CdSe NC film with a similarly deposited Cu2Se film demonstrated usefulness of the CdSe NC films synthesized using the present technique for practical applications.

Facile synthesis of plate-like CuS nanoparticles and their optical and photo-thermal properties

Plate-like CuS nanoparticles were prepared by a facile aqueous solution method using Radix Puerariae extract. The as-synthesized samples were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), UV-Vis-NIR spectroscopy, and energy-dispersive X-ray spectroscopy (EDS). The CuS films showed strong absorbance in the NIR region and moderate visible transmittance when mixed with PVA. Plate-like CuS nanoparticles were thus found to display great potential as NIR-shielding materials and good photo-thermal efficiency.

Effect of Na doping on structural, optical, and electrical properties of Cu2Se thin films prepared by chemical bath deposition method

In this work, pure and monovalent Na+ ion-doped Cu2Se thin films were deposited on glass substrates using a simple chemical bath deposition method and the films were annealed at 200 °C. The effect of Na+ doping on the structural, surface morphological, compositional, optical, and electrical properties of the Cu2Se thin films was investigated using X-ray diffraction, field-emission scanning electron microscopy (FESEM), diffuse reflectance spectra, and Hall effect analysis. The X-ray pattern reveals that both pure and Na+-doped Cu2Se thin films crystallized in cubic structure with a shift for Na-doped films indicating the incorporation of Na into host Cu2Se site. FESEM images show uniformly distributed multi geometrical shape particles. Na-doped films show higher absorption in the visible region. The energy bandgap is about 2.5–1.52 eV for Na-doped films. The films were found to be p type and the electrical conductivity of the doped films is found to be less than the Cu2Se films.

Super-hydrophilic copper sulfide films as light absorbers for efficient solar steam generation under one sun illumination

Solar steam technology is one of the simplest, most direct and effective ways to harness solar energy through water evaporation. Here, we report the development using super-hydrophilic copper sulfide (CuS) films with double-layer structures as light absorbers for solar steam generation. In the double-layer structure system, a porous mixed cellulose ester (MCE) membrane is used as a supporting layer, which enables water to get into the CuS light absorbers through a capillary action to provide continuous water during solar steam generation. The super-hydrophilic property of the double-layer system (CuS/MCE) leads to a thinner water film close to the air-water interface where the surface temperature is sufficiently high, leading to more efficient evaporation (∼80 ± 2.5%) under one sun illumination. Furthermore, the evaporation efficiencies still keep a steady value after 15 cycles of testing. The super-hydrophilic CuS film is promising for practical application in water purification and evaporation as a light absorption material.

A novel electrochemiluminescence system of CuS film and K2S2O8 for determination of crystal violet

A novel electrochemiluminescence (ECL) system that consists of the copper sulphide (CuS) film and K2S2O8 was prepared and used for detecting crystal violet in aqueous solutions. The CuS film was a luminescent semiconductor material, which was modified on glassy carbon electrode (GCE) via one-step electrodeposition. To enhance the ECL intensity, K2S2O8 was added into the solution. The morphology and composition of the modified electrodes were analyzed with scanning electron microscope, energy-dispersed spectrum, transmission electron microscope, high resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy. Electrochemical impedance spectroscopy (EIS) was studied for different electrodeposition time. Under the optimal conditions, the ECL intensity of the quenching value (ΔECL) versus the logarithm of the concentration of crystal violet was linear over a concentration range from 5.0×10−8 to 1.0×10−5mol L−1 (r=0.9926) and the limit of detection (LOD) was up to 3.2×10−9mol L−1.

Chemical spray pyrolysis synthesis of covellite copper sulphide (CuS) thin films for economical counter electrode for DSSCs

Thin films of covellite copper sulphide (CuS) were deposited on FTO substrates using chemical spray pyrolysis technique. Influence of Cu-to-S molar ratio on structural, surface morphological, optical and electrical properties were systematically investigated using variety of characterization techniques. Formation of covellite CuS films was confirmed by low angle-XRD and Raman spectroscopy. The field emission scanning electron microscopy analysis revealed the formation of faceted CuS particles without secondary growth. Optical studies exhibited decrease in optical band gap (from 2.21 to 1.69 eV) with increase in Cu-to-S molar ratio. Electrical properties were investigated using Van der Pauw four point probe method and Hall measurements revealed that as-synthesized CuS films have low sheet resistance (1.47–2.45 Ω/□), high carrier mobility (8.90–54.89 cm2/Vs) and high sheet concentration (1016–1018/cm2). The CuS films deposited at optimized Cu-to-S molar ratio (1:2.5) were then further studied for electrochemical impedance spectroscopy and photovoltaic characteristics. A quantum-dot sensitized solar cell incorporating optimized CuS film as counter electrode showed power conversion efficiency of ~ 1.05% with Voc ~ 0.46 V, Isc ~ 1.01 mA/cm2 and fill factor ~ 0.34%. Although the cell is not fully optimized and better results can be anticipated.

Improved performance of CdSe/CdS co-sensitized solar cells adopting efficient CuS counter electrode modified by PbS film using SILAR method

In this paper, CuS film was deposited onto fluorine-doped tin oxide (FTO) substrate using a facile chemical bath deposition method, and then modified by PbS using simple successive ionic layer absorption and reaction (SILAR) method with different cycles. These CuS/PbS films were utilized as counter electrodes (CEs) for CdSe/CdS co-sensitized solar cells. Field-emission scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer was used to characterize the CuS/PbS films. The results show that CuS/PbS (10 cycles) CE exhibits an improved power conversion efficiency of 5.54% under the illumination of one sun (100 mW cm−2), which is higher than the CuS/PbS (0 cycles), CuS/PbS (5 cycles), and CuS/PbS (15 cycles) CEs. This enhancement is mainly attributed to good catalytic activity and lower charge-transfer and series resistances, which have been proved by electrochemical impedance spectroscopy, and Tafel polarization measurements.

Photo-thermal and cytotoxic properties of inkjet-printed copper sulfide films on biocompatible latex coated substrates

Inkjet-printing of metal nanoparticles is a particularly promising technique for the fabrication and modification of surfaces with a multifunctional nature. Recently copper sulfide nanoparticles (CuS NPs) have attracted wide interest due to a range of valuable properties including long term stability, photo-thermal activity, ease of synthesis and low cost. In the present study, printed CuS patterns were successfully fabricated on latex coated paper substrates and characterized by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis-NIR spectroscopy, and grazing incidence X-ray diffraction (GID). The resulted patterns displayed pronounced photo-thermal effect under Near Infrared Irradiation (NIR) even with relatively low laser power. Finally, by utilizing an automated real-time imaging platform it was possible to verify that the CuS printed film was not cytotoxic to human dermal fibroblast cells (HDF). The pronounced photo-thermal properties and nontoxic nature of these printed low-cost flexible CuS films make them promising candidates for fabrication of devices with localized photo-thermal effect suitable for biomedical applications.

CTAB-assisted hydrothermal synthesis of Cu2Se films composed of nanowire networks

A simple hydrothermal method has been developed to synthesize Cu2Se film on copper foil with the assistance of cetyltrimethylammonium bromide (CTAB) as a surfactant. The Cu2Se film was constructed by novel nanowire networks with length up to 50µm. The obtained product was characterized by XRD, SEM, HRTEM, Raman, and XPS techniques, revealing that Cu2Se nanowire possessed single-crystal structures. The shape of Cu2Se film changed from nanowire networks to perfect microflowers as the amount of CTAB increased. Such Cu2Se film may have great potential applications in biomedical engineering, sensors, and catalysis.

Facile synthesis of morphology dependent CuS nanoparticle thin film as a highly efficient counter electrode for quantum dot-sensitized solar cells

Copper sulfide (CuS) thin films with a nanoparticle structure on a fluorine-doped tin oxide (FTO) substrate prepared by facile chemical bath deposition (CBD) at different growth times were used as the CE for QDSSCs. The morphology of the CuS CE was controlled well by the electrochemical growth time. Here, the CuS thin films deposited for 2h (CuS2h) CE and TiO2/CdS/CdSe/ZnS QD sensitized cell exhibited superior electrochemical and photovoltaic performance with Jsc, Voc, and FF values of 15.52mAcm−2, 0.612V, and 0.452, respectively, and an efficiency (η) of 4.29%, whereas the cell with the Au CE delivered an η of only 2.19% under the same conditions. Electrochemical impedance spectroscopy and Tafel polarization showed that the CuS film deposited at 2h possesses fascinating electrocatalytic activity for the S2−/Sn2− redox couple in a polysulfide electrolyte solution that was superior to Au CE. In addition, the stability test conducted for both CuS and Au-based devices for approximately 45h under the one sun illumination confirmed that the long-term stability of the CuS film decreased by 12% (4.31–3.79%), whereas that of the Au based cell decreased by 9.6% (2.19–1.98%) from 0 to 45h.

Antifriction effects of Cu2S film on Ni-based MMC coating

Self-lubricating sulfide films have gained increasing interest because of their outstanding properties and promising functions in a wide range of applications. In this study, thin cuprous sulfide (Cu2S) films with a 13μm thickness were produced on Ni55 substrates by low temperature ion sulfurizing to reduce wear and tear to the Ni55 coatings.The Cu2S film is composed of polygonal micro-rods that were constructed from successive Cu2S nano-sheets with SEM. The antifriction effects of the film were conducted by ball-on-disk dry sliding tests using various loads and speeds under dry friction conditions. The results indicated that the Cu2S film showed enhanced antifriction performance by significantly reducing the friction coefficients and the depths of wear. With the help of copper particles formed by cuprous sulfide and oxygen, the Cu2S film is able to separate the friction pairs from each other. Also, coating them with the film can significantly reduce the wear and tear to composite coatings caused by the plowing action of debris from the Ni55 coatings.

Influence of trivalent (Bi, Sb) metal ions on the photosensitivity of doped Cu2Se thin films

In this work pure and trivalent (Bi and Sb) ions doped copper selenide (Cu2Se) thin films were prepared by chemical bath deposition. The effect of structural, morphological and optical properties of trivalent doped Cu2Se thin films were analyzed by X-ray diffraction (XRD) patterns, scanning electron microscope (SEM), diffuse reflectance spectroscopy technique. XRD analysis shows the formation of cubic structure of Cu2Se thin film and the trivalent doping slightly suppress the intensity of the polycrystalline peaks with shift in the major peak position. SEM images shows well defined spherical grains population are more over the surface. The homogeneous Cu2Se films formation is witnessed by field emission SEM and transmission electron microscopy analysis. The pure and Bi doped Cu2Se thin films show higher absorption in the visible region than the Sb doped Cu2Se thin films. The band gap is found to be in the range of 1.70–2.33 eV. The Bi doped films shows higher photo sensitivity.

Controllable Formation of Efficient CuSe Counter Electrodes for Quantum Dot Sensitized Solar Cells

We report a novel method to prepare efficient CuSe counter electrodes for quantum dot sensitized solar cells. The CuSe films are deposited on fluorine doped tin oxide substrates using a two-step solution-based method. The unique morphology and excellent catalytic property of the CuSe films are characterized thoroughly. Employing this novel counter electrode, the CdSe quantum dot sensitized solar cells exhibit the best power conversion efficiency of 5.77%, outperforming the reference devices applying Cu2S counter electrodes. The preparation method is transferable to fabricate other metal selenide functional electrodes, promising a broader application in solar cells.

Highly flexible, transparent and conducting CuS-nanosheet networks for flexible quantum-dot solar cells.

The rapid development of modern electronics has given rise to a higher demand for flexible and wearable energy sources. Flexible transparent conducting electrodes (TCEs) are one of the essential components of flexible/wearable thin-film solar cells (SCs). In this regard, we present highly transparent and conducting CuS-nanosheet (NS) networks with an optimized sheet resistance (Rs) as low as 50 Ω sq-1 at 85% transmittance as a counter electrode (CE) for flexible quantum-dot solar cells (QDSCs). The CuS NS network electrode exhibits remarkable mechanical flexibility under bending tests compared to traditional ITO/plastic substrates and sputtered CuS films. Herein, CuS NS networks not only served as conducting films for collecting electrons from the external circuit, but also served as superior catalysts for reducing polysulfide (S2-/Sx2-) electrolytes. A power conversion efficiency (PCE) up to 3.25% was achieved for the QDSCs employing CuS NS networks as CEs, which was much higher than those of the devices based on Pt networks and sputtered CuS films. We believe that such CuS network TCEs with high flexibility, transparency, conductivity and catalytic activity could be widely used in making wearable electronic products.

Fabrication and characterization of p-CuS/n-GaN thin film heterojunction diodes

Abstract The p-CuS/n-GaN heterojunctions were fabricated successfully using RF magnetron sputtering. It was found that the properties of CuS films with annealing treatment were superior to non-annealed ones through various tests of SEM, XRD, Raman, EDS, and absorption spectrum. The optical band-gap slightly increased after annealing treatment. The current-voltage (I–V) characteristics of p-CuS/n-GaN heterojunction were measured and showed well-defined rectifying behavior for the annealed device.

Facile synthesis of porous CuS film as a high efficient counter electrode for quantum-dot-sensitized solar cells

In this paper, porous CuS film has been successfully prepared by a facile method and employed as a counter electrode (CE) in quantum-dot-sensitized solar cells (QDSSCs) for its highest catalytic activity. This CuS thin film was deposited on FTO substrate via spin coating process which is simple to operate, and its electrochemical properties were further studied by EIS and Tafel measurement. With the cycling time of depositing CuS up to 8, it displays high electrocatalytic activity toward polysulfide reduction, rationalizing the improved QDSSCs performance. Using the CdS/CdSe-sensitized QDSSCs, the cells exhibit improved short-circuit photocurrent density (Jsc) and fill factor (FF), achieving solar cell conversion efficiency (η) as high as 5.60 % under AM 1.5 illumination of 100 mW cm−2. This work provides a novel and simple method for the preparation of CEs, which could be utilized in other metal sulfides CEs for QDSSCs.

A new probe into thin copper sulfide counter electrode with thickness below 100 nm for quantum dot-sensitized solar cells

Currently, most of CuS counter electrodes (CEs) used in quantum dot-sensitized solar cells (QDSSCs) are provided with a thickness of hundreds of nanometers or even several microns. Considering the CE with low thickness having many advantages, thin CuS films with thickness ranging from 47nm below to 115nm have been synthetized in this paper via chemical bath deposition (CBD) method with different bath concentrations. A power conversion efficiency (PCE) of 3.25% has been achieved utilizing CuS thin films a thickness of only 64nm as CEs in QDSSCs without any structural optimization, which is higher than the value of the cell employing CuS CE with thickness of 2.8μm. Electrochemical impedance spectroscopy, Tafel polarization, and two-point current-voltage measurements are used to investigate the electrocatalytic and conductive performance of CuS CEs with different thickness. Owing to the highest electrocatalytic capacity and good conductivity of the 64 nm-thick CuS CE, QDSSC assembled with this CE has reached relatively high PCE under one sun illumination (100mWcm−2, AM 1.5). In addition, cyclic voltammetry measurements indicate that the thin CuS CE has a good stability against the polysulfide electrolyte.

XRD Raman analysis and optical properties of CuS nanostructured film

Raman spectroscopy and X-ray diffraction (XRD) methods were applied to determine the phase composition and crystal quality of CuS nanostructured film grown by spray pyrolysis.The film has polycrystalline structure with preferential growth along the (101) plane. The grain size for the film was found to be lower than 20nm. The very sharp Raman peak around 470cm−1 in the high frequency region was identified as the SS stretching mode of S2 ions at the 4e sites. Other Raman peaks were around 266cm−1, 118cm−1 and 68cm−1 in the low frequency region due to CuS phase. Particles of nanometric size show low wavenumber vibrational modes that can be observed by Raman spectroscopy. Optical properties were obtained from UV–vis absorption, transmittance and reflectance spectra of the nanostructured CuS film. The optical constants of the film such as refractive index, extinction coefficient and, optical conductivity were investigated. The film was found to be p-type by using hot probe method.