CuS Films Research Articles

Synthesis and characterization of arrested precipitation assembled Cu2Se thin films

Nanostructured thin films of copper selenide (Cu2Se) deposited by arrested precipitation technique (APT) with controlled release of ions at suitable pH=10.5. The deposited Cu2Se films were characterized for optical, structural, and morphological properties. Optical absorption study indicates that the band gap energy (2.26 eV) of material and shows visible radiation absorption. XRD shoe that APT is a favorable technique for the synthesis of pure nanocrystalline Cu2Se thin films with monoclinic crystal structure. An electrochemical impedance spectroscopy analysis confirms the charge transfer resistance. X-ray photoelectron spectroscopy reveals stoichiometry at valance state of Cu2Se.

Synthesis and characterization of arrested precipitation assembled Cu2Se thin films

Nanostructured thin films of copper selenide (Cu2Se) deposited by arrested precipitation technique (APT) with controlled release of ions at suitable pH=10.5. The deposited Cu2Se films were characterized for optical, structural, and morphological properties. Optical absorption study indicates that the band gap energy (2.26 eV) of material and shows visible radiation absorption. XRD shoe that APT is a favorable technique for the synthesis of pure nanocrystalline Cu2Se thin films with monoclinic crystal structure. An electrochemical impedance spectroscopy analysis confirms the charge transfer resistance. X-ray photoelectron spectroscopy reveals stoichiometry at valance state of Cu2Se.

Effect of molar concentration on the structural, linear and nonlinear optical properties of CuS (covellite) thin films

CuS thin films with various molar concentrations at 70 °C temperature were deposited by Chemical Bath Deposition. The effect of molar concentration on the structural, linear optic, nonlinear optic and morphological properties of CuS films were deeply investigated. X-ray diffraction (XRD) analysis exhibited that CuS films were formed in polycrystal structure and hexagonal phase. The fundamental optical parameters of films such as energy band gap, reflection and extinction coefficient were determined with the results of optical transmission and optical absorption by UV–vis spectrophotometer. The energy band gap values were reduced with increasing films thickness. Moreover, the dependence of the optical dielectric constants, loss tangent, optical conductivity, surface and volume energy loss function values on the molar concentrations were studied. Furthermore, the third order nonlinear optical susceptibility and nonlinear refractive index, which is considered to be the base of the first order optical susceptibility with nonlinear optical properties were discussed in detail.

Synthesis and characterization of nanoparticles of semiconducting metal suplhide and their application

Cadmium Sulphide (CdS) [II-VI group n-type semiconductor] and Copper Sulphide (Cu2S) [I-VI group p-type semiconductor] have large commercial applications like solar cell, gas sensor etc. Wide band gap CdS semiconductor was used as the transparent window material together with narrow band gap Cu2S semiconductor used as the absorber layer. Thioglycerol capped CdS and Cu2S nanoparticles were synthesized by using the non-aqueous chemical method at room temperature. CdS and Cu2S films were prepared on fluorine doped tin oxide (FTO) glass substrates by using the simple dip coating method at different dip times and heat treated in air. CdS and Cu2S nanoparticles were analysed by Ultraviolet-Visible absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). CdS and Cu2S films were investigated by scanning electron microscopy (SEM), energy dispersive analysis by x-rays (EDAX), mapping and atomic force microscopy (AFM). Thicknesses of films were determined using laser profilometer. Previously, preparation of solar cells using CdS and Cu2S films deposited by dip coating method has not been reported. In this study, thin-film solar cells with p-n heterojunction having enhanced conductivity, excellent solar energy conversion efficiency, enhanced fill factor, low cost and easy fabrication were prepared to increase the quality of solar cells.

Realizing high thermoelectric performance in highly (0l0)-textured flexible Cu2Se thin film for wearable energy harvesting

Searching for eco-friendly and earth-abundant materials to supersede traditional high-cost bismuth telluride for fabricating wearable devices is of great significance in thermoelectrics. In this work, promising flexible Cu2Se based thin films with high thermoelectric performance is successfully fabricated via a facile co-sputtering method. Experimental results indicate that excess Cu in Cu2Se films leads to the decrease of carrier concentration by suppressing the formation of Cu vacancies and donating electrons, benefiting to achieve high Seebeck coefficient. Moreover, Cu-excess Cu2Se films have highly (0l0) preferred orientation and extra high carrier mobility, maintaining the decent electrical conductivity in the whole measurement temperature range. Combined with the low thermal conductivity, a maximum ZT of 0.42 is obtained at 275 °C from the Cu-excess Cu2Se due to the simultaneous optimization both of electrical and heat transport. Subsequently, a flexible thermoelectric device assembled with high performance Cu2Se films exhibits a maximum power density of 4.28 Wm-2 at a temperature difference of 50 °C, which thermal stability is greatly improved after introducing a molybdenum buffer layer into electrode layer. Therefore, this work demonstrates that rational microstructure manipulations and connection technology improvement can achieve high performance in the flexible thermoelectric device, which possess potential in wearable applications.

Optical, Structural and Electrical Properties of CuS Thin Film on Dielectric Substrate by Spray Pyrolysis Technique

Abstract: This paper deals with depositing a CuS thin film on a glass substrate at 3800C by using spray pyrolysis method. Its optical properties and electric properties are characterized after cooling the sample. Formation for compound, structure and morphology were studied using x-ray diffraction. The optical study comprised the extraction and analysis of calculated optical constants, such as absorption coefficient (α), transmittance, extinction coefficient (k), which revealed the presence of a direct optical energy band gap of 2.0 eV. The temperature-dependent electrical resistivity with other necessary parameters was systematically studied for CuS film in the present work. Overall study confirmed the semiconducting behavior of the film which is useful for many applications, even when the film is touching the substrate at a micrometer scale with spray pyrolysis. This paper also explores the optical conductivity, dielectric constant, Urbach energy, morphology and thermal activation energy of the CuS film with explaining methodological details. Keywords: Thin film, Spray pyrolysis technique, Electrical and optical properties, XRD.

Flexible pCu2Se-nAg2Se thermoelectric devices via in situ conversion from printed Cu patterns

Flexible thermoelectric (TE) devices have great potential in wearable electronics, but there is great challenge to realize robust TE device with high performance via feasible integration process. Herein, based on precisely printed copper patterns, a flexible pCu2Se-nAg2Se TE device is initially realized by in situ ion exchange reaction. The as-prepared Cu2Se and Ag2Se films possess typical hierarchical defects including atomic scale vacancies, the nanosheet fragments and microscale porous structure, which could significantly scatter phonons in wide frequency range. Accordingly, ultra-low thermal conductivity (Cu2Se: 0.13 W m−1 K−1; Ag2Se: 0.15 W m−1 K−1) and optimal ZTs (Cu2Se: 0.5; Ag2Se: 0.7) are achieved. Meanwhile, the as-fabricated pCu2Se-nAg2Se TE device exhibits an excellent power density of 13.4 W m−2 at a temperature gradient of 40 K, which is among the highest values of printed in-plane film devices. Furthermore, the good adhesion between TE films and porous PI substrate endowed excellent flexibility and stability of pCu2Se-nAg2Se devices.

Scalability of copper selenide (CuSe) thin films using electrodeposition technique with three electrode configurations for solar energy applications

In this work, copper selenide was synthesized potentiostatically at varied voltage on conductive FTO substrate of dimension 2 by 2.4 cm2 with three electrode configurations in which graphite was selected as working electrode (cathode), carbon as counter electrode (anode) and Ag/AgCl as reference electrode. In order to synthesis stoichiometric CuSe films as a good alternative window layer material with unique properties for diverse of applications, we therefore employed electrodeposition (ED) technique owing to its scalability and self- purification capability. We employed X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), x-ray fluorescence (XRF) and ultraviolet visible spectrophotometer (UV) to study the material properties and the film suitability in solar cells fabrication.

Preparation and performance of g-C3N4/CuS film as counter electrode for quantum dot sensitized solar cells

In this work g-C3N4/CuS composite film was prepared by successive ion layer adsorption and reaction (SILAR) method and used as the counter electrode in quantum dot sensitized solar cell (QDSSCs). To configure the cell, CdSe and CdS quantum dots acted as sensitizers on the photoanode side, polysulphide was used as the electrolyte and copper sulphide was deposited into the g-C3N4 film structure on the counter electrode side. Scanning electron microscope and X-ray diffraction were used to characterize the morphology and structure of the electrode materials, respectively. The photovoltaic performance of the cell was analysed by a standard solar simulator. The results revealed that the photoelectric conversion efficiency of the cell reached 3.65% under condition of AM 1.5 and irradiation intensity of 100mW/cm2.

Sample preparation induced phase transitions in solution deposited copper selenide thin films.

Thin films of CuSe were deposited onto GaAs substrate. XRD showed that the as-deposited films were of the Klockmannite (CuSe – P63/mmc 194) phase with lattice parameters a0 = b0 = 0.3939 nm, c0 = 1.7250 nm; however, electron diffraction in the TEM surprisingly indicated the β-Cu2−xSe phase (Cu1.95Se – R3̄m 166) with lattice parameters a0 = b0 = 0.412 nm, c0 = 2.045 nm. The discrepancy originated from the specimen preparation method, where the energy of the focused ion beam resulted in loss of selenium which drives a phase transition to β-Cu2−xSe in this system. The same phase transition was observed also upon thermal treatment in vacuum, as well as when the 200 keV electron beam was focused on a powder sample in the TEM. The initial phase can be controlled to some extent by changing the composition of the reactants in solution, resulting in thin films of the cubic α-Cu2−xSe (Cu1.95Se – Fm3̄m) phase co-existing together with the β-Cu2−xSe phase.

High thermoelectric performance of Cu2Se-based thin films with adjustable element ratios by pulsed laser deposition

Copper selenide (Cu2Se) is a P-type thermoelectric (TE) semiconductor that is environmentally friendly and has rich crust content and high cost performance–price ratio. Present studies on Cu2Se focus on the high TE performance of the bulks because of the intrinsic low thermal conductivity resulting from the ‘liquid-like’ behavior of Cu ions. Compared with three-dimensional bulks, two-dimensional thin films are more compatible with modern semiconductor technology and have unique advantages in the construction and application of TE micro- and nano-devices. In this study, b-axis–oriented Cu2Se epitaxial thin films were successfully prepared using pulsed laser deposition (PLD) technology. The element ratios (Cu:Se) were adjusted in a small range (2.0:0.899–0.942). Correspondingly, the Cu vacancy concentration was optimized by changing the deposition temperature of the substrate. The in-plane directional power factor of the thin film is as high as ∼20.02 μW/cm K−2 at 580 K and ∼8.44 μW/cm K−2 at room temperature, which are higher than that of Cu2Se bulks. As per theoretical calculation, the estimated zT value of the Cu2Se film with a thickness of 295.0 nm reaches ∼0.58 at 580 K. The relatively high TE performance and good repeatability demonstrate that Cu2Se films have great application potential in solid-state refrigeration and power generation. The PLD preparation and performance control methods involved in this research will promote the development of high-performance Cu2Se films and devices.

Optical and electrical dynamics at the In/CuSe interfaces

Herein, thin films of copper selenide are coated onto glass and 150 nm thick transparent indium substrates. The effect of indium substrates on the structural, morphological, compositional, optical, dielectric and electrical properties of CuSe are explored. Replacement of glass by indium, increased the crystallite and grain sizes, decreased the micro-strains, the stacking faults, the stress and the defect densities. Remarkable change in the shape of grains from wire like to rectangular shaped is forced by indium. Indium substrates also caused shrinkage in the energy band gap, enhanced the light absorbability and increased the dielectric constant values. The Drude-Lorentz analyses on the dielectric spectra have shown that the replacement of glass by indium increases the optical conductivity, increases the scattering time constant at femtosecond level and widens the range of plasma frequencies. On the other hand, dynamical electrical measurements which were carried out for In/CuSe/In devices, reveal the ability of using CuSe active media for fabrication of negative capacitance thin film transistors. Hopping conduction of charged particles over correlated barriers of height of 0.26 eV is dominant in the In/CuSe/In devices. The impedance spectroscopy analyses have shown that CuSe films can be used as bandstop filter appropriate for 5 G technologies.

Influence of Cu content on the phase composition and thermoelectric properties of deposited Cu-Se films

In this study, the p-type Cu-Se films with different Cu contents were prepared on SiO2/Si substrates by magnetron sputtering using targets with different atomic ratio ([Cu]/[Se]) of Cu to Se. The relation of Cu content and phase composition in Cu-Se films was systematically studied. The deposited films took place phase transformation from p-CuSe2 to p-CuSe2+γ-CuSe, to γ-CuSe, to γ-CuSe+β-Cu2-xSe, to β-Cu2-xSe, to α-Cu2Se+unknown, to α-Cu2Se+unknown+Cu phase with increasing [Cu]/[Se] in the deposited films from 0.49 to 5.74. At room temperature, the carrier concentration decreases in the order of the CuSe2, CuSe and β-Cu2-xSe phase; but the carrier mobility exhibits an opposite trend. In the studied temperature range, the Seebeck coefficient and the power factor decreases in the order of β-Cu2-xSe, CuSe2 and CuSe phase. The [Cu]/[Se] in deposited films with single β-Cu2-xSe phase exceeds 2.0 of stoichiometric lattice and Cu-rich β-Cu2-xSe phase films forms. The deposited Cu-rich β-Cu2-xSe phase film with [Cu]/[Se]=2.65 has an optimum Seebeck and resistivity value, reaching a high power factor of 2.88 mW·m−1·K−2 at RT and 5.91 mW·m−1·K−2 at 320°C. It is of the guidance meaning for the further study the thermoelectric properties of Cu-Se films in the future.

Preparation of (111)c-oriented Cu2Se films by pulsed laser deposition method

In this study, the low-temperature phase α-Cu2Se target with nearly ideal chemical stoichiometric ratio was synthesized through solid reaction process. After that, a series of pure and oriented α-Cu2Se films on single crystal Si (111) was prepared using pulsed laser deposition method, by carefully choosing the appropriate experimental parameters. Despite the increase of deposition time, the chemical composition, the crystal microstructure and the orientation of α-Cu2Se films keep the same. X-ray diffraction (XRD) and energy dispersive X-ray spectrometer show that all the α-Cu2Se films have the uniformity of chemical composition, without any other impurities. Scanning electron spectroscopy and high resolution transmission electron microscopy reveal that α-Cu2Se are stacked nanosheets with exposed crystal planes (111)c. Particularly, the (111)c planes are parallel to Si substrate surface proved by the results of XRD φ-scan and pole figure. This report is a further step to realize the adjustment of anisotropy of Cu2Se properties.

High-performance CuS/n-Si heterojunction photodetectors prepared by e-beam evaporation of Cu films as precursor layers

Transition metal dichalcogenides (TMDCs) are considered to be the most promising next-generation materials for electronics and optoelectronics due to their excellent properties. In this work, well-performing CuS films were prepared by e-beam evaporation of Cu films as precursor layers. Ag/n-Si/Al2O3/CuS/ITO heterojunction photodetector with high responsivity (0.41 A·W−1), detectivity (1.739 × 1011 Jones) and fast response speed (17 μs) at zero bias were prepared by optimising sulphuration temperature and using silicon wafers with inverted pyramid light-trapping structures as substrates. Besides, the photodetector exhibited excellent light absorption ability, with an EQE of 51.91% at 980 nm. All these results demonstrated that excellent photodetector materials can be obtained by using metal films as precursor layers, which provides novel ideas and methods for the synthesis of TMDCs materials.

Dual Role of Cu‐Chalcogenide as Hole‐Transporting Layer and Interface Passivator for p–i–n Architecture Perovskite Solar Cell

AbstractInorganic hole‐transport layers (HTLs) are widely investigated in perovskite solar cells (PSCs) due to their superior stability compared to the organic HTLs. However, in p–i–n architecture when these inorganic HTLs are deposited before the perovskite, it forms a suboptimal interface quality for the crystallization of perovskite, which reduces device stability, causes recombination, and limits the power conversion efficiency of the device. The incorporation of an appropriate functional group such as sulfur‐terminated surface on the HTL can enhance the interface quality due to its interaction with perovskite during the crystallization process. In this work, a bifunctional Al‐doped CuS film is wet‐deposited as HTL in p–i–n architecture PSC, which besides acting as an HTL also improves the crystallization of perovskite at the interface. Urbach energy and light intensity versus open‐circuit voltage characterization suggest the formation of a better‐quality interface in the sulfide HTL–perovskite heterojunction. The degradation behavior of the sulfide‐HTL‐based perovskite devices is studied, where it can be observed that after 2 weeks of storage in a controlled environment, the devices retain close to 95% of their initial efficiency.

Study of CuS Thin Films Deposited by PLD Simulated for Prism Based SPR Sensor

Copper Sulfide CuS thin film was prepared using pulsed laser deposition PLD technique and characterized by X-ray and SEM. The optical, structural, and morphological properties are examined at different energies 500 mJ, 600 mJ, 700 mJ, and 800 mJ. The best result was 600 mJ which annealed at various annealing temperatures 300°C, 350°C, 400°C, and 450°C. The effect of thermal annealing on CuS thin film was examined X-ray and SEM. CuS Film was simulated using a prism-based SPR optical sensor. This paper introduces the optical test study of CuS thin film deposited by pulsed laser deposition technique on the quartz substrate and supported by theoretical application study under the effect of surface plasmon resonance (SPR). In this research field, the optical and morphological characteristics of the CuS thin film were deposited by PLD at different laser energies. The annealing process was applied for better-deposited thin-film; the XRD results, SEM images, transmittance T%, and energy gap Eg were analyzed thoroughly and compared to evaluate the thin-film. This effort was made in an in-depth analysis of CuS thin film deposited by PLD on the quartz substrate and applied theoretically in surface plasmon application.

Greatly improved NIR shielding performance of CuS nanocrystals by gallium doping for energy efficient window

In this work, gallium doped copper sulfide (Ga-doped CuS) nanocrystals were prepared using a solvothermal method. The effects of Ga doping on the crystal structures, chemical composition, morphology, optical properties and thermal performance of copper sulfide (CuS) were investigated. The Ga-doped CuS nanocrystals had a hexagonal structure comparable to that of pure CuS. The Cu+/Cu2+ ratio first decreased and then increased with increasing Ga3+ doping. Both CuS and Ga-doped CuS exhibited nanoplate and nanorod morphologies. The visible transmittance of the Ga-doped CuS films was in the range of 61–77.1%. Importantly, the near-infrared (NIR) shielding performance of the films can be tuned by adjusting the concentration of the Ga dopant. The NIR shielding value of the optimal Ga-doped CuS film was 72.4%, which was approximately 1.5 times as high as that of the pure CuS film. This can be ascribed to the enhanced plasmonic NIR absorption that resulted from an increase in the hole concentration after doping with Ga3+ ions. In the thermal performance test, the Ga-doped CuS film lowered the interior temperature of the heat box by 9.1 °C. Therefore, the integration of good visible transmittance and high NIR shielding performance make the Ga-doped CuS nanocrystals a promising candidate for energy-efficient window coatings.

Thermoelectric Properties of Cu2Se Nano-Thin Film by Magnetron Sputtering.

Thermoelectric technology can achieve mutual conversion between thermoelectricity and has the unique advantages of quiet operation, zero emissions and long life, all of which can help overcome the energy crisis. However, the large-scale application of thermoelectric technology is limited by its lower thermoelectric performance factor (ZT). The thermoelectric performance factor is a function of the Seebeck coefficient, electrical conductivity, thermal conductivity and absolute temperature. Since these parameters are interdependent, increasing the ZT value has always been a challenge. Here, we report the growth of Cu2Se thin films with a thickness of around 100 nm by magnetron sputtering. XRD and TEM analysis shows that the film is low-temperature α-Cu2Se, XPS analysis shows that about 10% of the film’s surface is oxidized, and the ratio of copper to selenium is 2.26:1. In the range of 300–400 K, the maximum conductivity of the film is 4.55 × 105 S m−1, which is the maximum value reached by the current Cu2Se film. The corresponding Seebeck coefficient is between 15 and 30 µV K−1, and the maximum ZT value is 0.073. This work systematically studies the characterization of thin films and the measurement of thermoelectric properties and lays the foundation for further research on nano-thin-film thermoelectrics.

3D Hierarchical Nanocrystalline CuS Cathode for Lithium Batteries.

Conductive and flexible CuS films with unique hierarchical nanocrystalline branches directly grown on three-dimensional (3D) porous Cu foam were fabricated using an easy and facile solution processing method without a binder and conductive agent for the first time. The synthesis procedure is quick and does not require complex routes. The structure and morphology of the as-deposited CuS/Cu films were characterized by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron spectroscopy, respectively. Pure crystalline hexagonal structured CuS without impurities were obtained for the most saturated S solution. Electrochemical testing of CuS/Cu foam electrodes showed a reasonable capacity of 450 mAh·g−1 at 0.1 C and excellent cyclability, which might be attributed to the unique 3D structure of the current collector and hierarchical nanocrystalline branches that provide fast diffusion and a large surface area.