CFTS Thin Films Research Articles

Synthesis of Single Crystal 2D Cu2FeSnS4 Nanosheets with High-Energy Facets (111) as a Pt-Free Counter Electrode for Dye-Sensitized Solar Cells.

Two-dimensional Cu2FeSnS4 (CFTS) nanosheets with exposed high-energy facets (111) have been synthesized by a facile, scalable, and cost-effective one-pot heating process. The CFTS phase formation is confirmed by both X-ray diffraction and Raman spectroscopy. The formation mechanism of exposed high-energy facet CFTS growth is proposed and its electrochemical and photoelectrochemical properties are investigated in detail to reveal the origin of the anisotropic effect of the high-energy facets. Dye-sensitized solar cells (DSSC) achieve a favorable power conversion efficiency of 5.92% when employing CFTS thin film as a counter electrode, suggesting its potential as a cost-effective substitute for Pt in DSSCs.

Growth and characterization of Cu2ZnxFe1-xSnS4 thin films deposited on n-type silicon substrates

Cu2FeSnS4 and Cu2ZnSnS4 ingots were successfully grown by direct melting of their high-purity constituent elements from stoichiometric compositions (copper, iron, zinc, tin and sulfide). Subsequently, thin films of CFTS and CZTS were deposited on unheated n-type silicon substrates through the vacuum evaporation method. These deposited films were sulfided for 30 min at a sulfidation treatment temperature Ts = 400 °C. The structural properties of the C (Z, F)TS thin films were studied by X-ray diffraction (XRD), Raman spectroscopy and electron backscatter diffraction (EBSD).The resulting studies suggest the existence of polycrystalline phases where CZTS has a kesterite structure and CFTS a stannite structure. Composition analysis also indicates that the synthesized C (Z,F)TS powders are close to the expected stoichiometry.A good crystallinity of CZTS followed by an increase in the average roughness value of this film is highlighted in the thin film micrographs of C (Z,F)TS. Furthermore, the Hall effect indicates that the prepared C (Z,F)TS films exhibit a manifest p-type semiconductor, and the conductivity, mobility and carrier charge concentration are higher for the CZTS thin film. The electrical conductivity of the CFTS and CZTS thin films were investigated using the impedance spectroscopy technique in the frequency range 5 Hz–13 MH. Values of activation energy are indicative of thermal activation of the conduction mechanism by jumping between localized states. Further, the analysis of the frequency and temperature dependence of the AC conductivity supports the correlated barrier hopping (CBH) model.

Influence of Laser Pulse Energy on CFTS Thin Film Deposited by Pulsed Laser Deposition

Influence of Laser Pulse Energy on CFTS Thin Film Deposited by Pulsed Laser Deposition

Synthesis and Characterization of Chemically Sprayed Cu<sub>2</sub>FeSnS<sub>4</sub> (CFTS) Thin Films: The Effect of Substrate Temperature

In this study, Cu2FeSnS4 (CFTS) thin films were deposited on glass substrates at different temperatures of 250, 300, 350, 400, and 450 °C using the chemical pyrolysis technique. This work aimed to study the effect of substrate temperature on film properties. The film's structural properties were obtained via X-ray diffraction, Raman spectroscopy, and Field Emission Scanning Electron Microscopy (FESEM). The UV-Vis spectrum determined the optical properties; and the electrical properties were obtained through observation of the Hall effect. Analysis of XRD pattern showed that the CFTS thin films have a tetragonal structure with a main peak corresponding to the direction (112). Results of Raman spectroscopy displayed a unique peak at 318 cm-1, suggesting a quaternary compound of CFTS. The FESEM tests confirmed the presence of nanoparticles of various shapes and sizes. The CFTS films have a band gap of 1.77-1.92 eV and an absorption coefficient in the visible spectrum region higher than 104 cm-1, which confirms their use as an active layer in solar cells. The mea measurements of the Hall effect of the CFTS thin films showed a p-type conductivity for all films, with the maximum charge carrier density and mobility occurring at 400 °C, making them suitable for photovoltaic applications.

A simple route for synthesis of copper iron tin sulfide thin films

Copper iron tin sulfide Cu2FeSnS4 (CFTS) thin films are prepared by a facile and low-cost route using sol-gel spin-coating method without a sulfurization step. The optimal condition for synthesis of CFTS thin films has been determined. X-ray diffraction and Raman spectroscopy analysis revealed that the formation of a pure phase of CFTS thin films at 400 °C for 40 min with a large crystallite size 60 nm. The morphological and chemical composition study indicates the formation of uniform, smooth, cracks free and nearly stoichiometric thin films. The films show p-conductivity, good optical and electrical properties; high absorption coefficient >104 cm−1 in visible region, band gap energy of about 1.5 eV, carrier density of 3.85 1016 cm−3 and low resistivity of 0.364 Ω.cm. The obtained physical properties of CFTS thin films are suitable for solar cell applications.

Photoactive Cu2FeSnS4 thin films: Influence of stabilizers

Quaternary photo-active metal chalcogenide Cu2FeSnS4 (CFTS) were deposited by the sol–gel method. The negative differential resistance (NDR) phenomenon and resistive switching (RS) characteristics at room temperature was observed on ITO/CFTS/Al device. The formation of CFTS was studied in the presence of different stabilizers like lactic acid and monoethanolamine. The use of dissimilar stabilizers has led to the change in the absorption and reflectance properties of the CFTS. The impact of stabilizer on the optical band-gap energy was enumerated from UV–Vis studies. The electrical bistability of these samples was studied amongst which the thin film fabricated with the aid of lactic acid exhibited better performance and can be extensively used for memory applications like random access memory (RAM) applications. Finally, the as-fabricated CFTS thin films were sulfurized and the photo-electrical properties were examined. From these studies, it is inferred that the electrical bistability vanishes after sulfurization. However, the photo-response of the sulfurized sample was improved when compared to its counterpart. These works provide a breakthrough for exploring the memory application of multifunctional material with further multiple physical attributes.

Growth of the next generation promising Cu2 Fe1-xCoxSnS4 thin films and efficient p-CCTS/n-In2S3/n-SnO2F heterojunction for optoelectronic applications

In this paper, we have elaborated Cu2Fe1-x CoxSnS4 (CFCTS) thin films (x = 0%, 25%, 50%, 75% and 100%) by spray pyrolysis technique on glass substrates. The effect of varying (Fe/Co) ratio on chemical composition, morphological, structural, optical and electrical properties has been investigated using energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements respectively. XRD results have shown that the change in (Fe/Co) ratio leads to the transformation of stannite CFTS (x = 0%) to stannite CCTS (x = 100%) with the same preferred orientation (112) plan. CFTS and CCTS phases have been confirmed by Raman peaks located respectively at 318 and 325 cm-1. A uniform and dense distribution of CCTS thin film were observed by scanning electron microscopy (SEM). Estimated band gap values of CFTS and CCTS thin films were equal to 1.46 eV and 1.32 eV respectively. Electrical resistivity value was decreased from 5.82 10-3 Ω.cm for CFTS thin film to 5 10-3 Ω.cm for CCTS thin film. These experimental results allow us to consider CFTS and CCTS as good candidates to be used as absorber materials in solar cell devices. Photocatalytic activities of CCTS thin film, CCTS/SnO2:F, CCTS/In2S3 and CCTS/In2S3/SnO2:F heterojunctions have been investigated under sun light irradiation using methylene blue (MB) as representative pollutant dye. It was found that the photodegradation rate was near to 86% in the presence of CCTS /In2S3 / SnO2:F heterojunction after 4 hours which leads to considering it as a good candidate to implement eco-friendly, sun-powered devices for removing organic pollution in waste water. for photocatalysis applications.

Structural, morphological and electrical properties of the Al/p-Cu2FeSnS4 thin film Schottky diode grown by two method

This work highlights some physical properties of Al/p-Cu2FeSnS4 Schottky diode fabricated by a two-stage method. Foremost, the Cu2FeSnS4 (CFTS) thin film was grown using thermal evaporation method onto heated Mo substrate temperature at 150 °C. After that, the as-deposited CFTS sample was annealed in a sulfur atmosphere at 400 °C for 30 min. Structural and morphological characterization were carried out by X-Ray diffraction, Raman scattering and scanning electron microscopy, whereas electrical study of Al/p-Cu2FeSnS4 junction was performed by using the current-voltage (I-V) measurement. Structural study revealed the presence of stannite CFTS phase and other peaks like Mo and MoS2. The hot probe method indicates that CFTS thin film exhibit p-conductivity type, also the film thickness was around 500 nm. The I-V characteristics showed that a Schottky contact was obtained between Aluminum and p-Cu2FeSnS4 absorber layer. The saturation current, the ideality factor and series resistance were determined from I-V experimental data. These parameters show important electrical properties such as a low series resistance and an ideality factor between 1 and 2.

Effect of sprayed volume on physical properties of Cu2FeSnS4 thin films and an efficient p-type Cu2FeSnS4/n-type F-doped SnO2 heterojunction

Quaternary chalcogenide Cu2FeSnS4 (CFTS) thin layers were successfully synthesized by a spray pyrolysis technique and deposited on glass substrates for different sprayed volumes (Vs = 300, 600, 900, and 1200 ml). Energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and Hall effect measurements were used to investigate, respectively, the chemical composition and the morphological, structural, optical, and electrical properties of CFTS thin films. XRD analysis and Raman spectroscopy revealed that the optimum growth of CFTS thin film occurred for Vs = 900 ml owing to the pure phase, good crystallinity, and maximum crystallite size estimated to be 62 nm. EDX analysis for Vs = 900 ml showed that the Cu/Fe/Sn/S stoichiometric ratio is close to the theoretical value of 2:1:1:4. The band gap and the electrical resistivity of the optimum film are 1.48 eV and 0.11 Ω cm, respectively. These experimental results allow us to consider CFTS thin film prepared with Vs = 900 ml as a promising absorber layer for solar cell applications. Furthermore, the optimum CFTS thin film exhibits good photocatalytic activity toward the degradation of methylene blue under sunlight irradiation. Moreover, a new heterojunction composed of CFTS and F-doped SnO2 was synthesized and studied. The photodegradation rate of methylene blue was 88%, which makes this heterojunction a promising alternative for removal of organic pollutants in wastewater treatment by photocatalysis.

Effect of substrate temperature on physical properties of Cu2FeSnS4 thin films for photocatalysis applications

Quaternary chalcogenide Cu2FeSnS4 (CFTS) thin layers have been grown by spray pyrolysis technique on glass substrates using different substrate temperatures (Ts = 160, 200, 240 and 280 °C). Physical properties of CFTS thin films were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), spectrophotometer and Hall Effect. All results suggest that CFTS thin film synthesized at Ts = 240 °C has the best physical properties. XRD indicates an enhancement of crystalline quality of stannite CFTS elaborated at Ts = 240 °C with a maximum grain size about 45 nm and Raman spectroscopy confirms the purity phase of optimum sample. At Ts = 240 °C, atomic ratios of Cu/Fe/Sn/S were close to the theoretical ratios 2/1/1/4 and SEM images illustrates that the surface of the film is covered from a large number of micro-aggregates with spherical form. It is found that energy band gap and absorption coefficient values were about 1.46 eV and 9.8 104 cm−1 respectively at Ts = 240 °C. Hall Effect measurements revealed that electrical resistivity of optimum sample decreased to 0.18 Ωcm. Thus, all experimental results demonstrate that CFTS thin film grown at Ts = 240 °C can be considered as a promising absorber material in solar cell devices. A higher photodegradation rate of MB was about 81% under sun light for 4 h which indicates that optimum CFTS thin film grown at Ts = 240 °C would be a cheaper alternative catalyst to replace TiO2 in photocatalysis applications.

Facile deposition and study of substrate temperature effect on the structural and physical properties of Cu2FeSnS4 (CFTS) thin films

Chalcogenide thin films of Cu2FeSnS4 (CFTS) were deposited through spray pyrolysis method, and effect of substrate temperature on the structure, morphology, optical, and electrical properties of the thin films was investigated. The samples were characterized by X-ray diffraction (XRD), UV–Vis spectroscopy, field emission scanning electron microscopy, and electrical measurements. XRD results describe the existence of the stannite phase of CFTS thin films, which is modified after increasing the substrate temperature. All polycrystalline thin films show peaks related to (112), (204), and (116) planes. FESEM images represent growth of the grains for higher substrate temperatures. Hall and Seebeck effect experiments confirm p-type conduction in all of the samples. The carrier density is found in the order of magnitude of 1020 cm−3 which increases by increasing the substrate temperature. Optical band gap measurements based on UV–Vis spectroscopy describe the values between 1.33 and 1.54 eV for all the samples. It is found that the CFTS absorber layers can be fabricated via facile method and their physical properties are adjustable through regulation of substrate temperature.

Synthesis of chemical spray pyrolyzed Cu2FeSnS4 thin films for solar cells

In this paper, we have successfully prepared Cu2FeSnS4 (CFTS) thin films by a facile spray pyrolysis method. In order to optimize the synthesis conditions of the CFTS thin films, two series of experiments were performed. In the first series, the thin films were deposited at a substrate temperature of 370 °C for different spray durations (td) of 20, 40 and 60 min. And in the second, the CFTS thin films were annealed in the sulfur atmosphere at a temperature of 450 °C for 30 min. Moreover, the X-ray diffractograms showed that the as-deposited and the post-annealed CFTS thin films revealed a stannite structure. The post-annealed CFTS thin films are considered as an ideal absorber in solar cells because of a large absorption coefficient (105 cm−1) and a direct band gap (1.55 eV). The activation energies Ea obtained from both angular frequency and DC conductivity are found to be 1 and 0.97 eV, respectively.

Influence of precursor thiourea contents on the properties of spray deposited Cu2FeSnS4 thin films

Semiconducting Cu2FeSnS4 (CFTS) thin films were spray-deposited with different thiourea contents in the precursor solution. The influence of thiourea contents (10–14 ml) in the precursor solution on the crystallographic, morphological, compositional, optical, electrical and thermoelectrical properties of CFTS films was studied. X-ray diffraction analysis confirmed stannite phase having tetragonal crystal structure. The surface of CFTS thin films had hexagonal crystals. Nearly stoichiometric deposition has been witnessed through energy dispersive X-ray spectroscopy. Optical bandgap was found to be in the range 1.54–1.76 eV based on the different thiourea contents in the precursor solution. The considerable reduction in electrical resistivity has been observed for TH13 sample. The CFTS thin films are p-type as confirmed from thermoelectrical analysis.

Electrical bistability and memory switching phenomenon in Cu2FeSnS4 thin films: role of p-n junction

Electrical bistability of Cu2FeSnS4 (CFTS) thin films fabricated via successive ionic layer adsorption and reaction (SILAR) method was studied here. The SILAR method is a simple and cost-effective method for large area thin film production. Though CFTS thin films have been fabricated for the last few years, neither the electrical memory applications nor the electrical bistability of these films has been studied yet. In this report, we have shown that the electrical characteristics of the CFTS films could be useful for the random-access memory (RAM) applications. A detailed investigation to understand the electrical bistability has been carried out. We found that conducting channels were formed inside the films when a suitable bias voltage is applied and that could be reset with an opposite bias voltage to establish electrical bistability. The p-n junction configuration restricted the percolation and formation of conducting filament. Thus, no electrical bistability were observed for the CFTS p-n junction.

Preparation and characterization of Cu2FeSnS4 thin films for solar cells via a co-electrodeposition method

Quaternary stannite semiconductor Cu2FeSnS4 (CFTS), which is an ideal material for solar photovoltaic cells, has attracted widespread attention. CFTS crystals have been successfully synthesized by the co-electrochemical deposition method. The structure, morphology, and composition of as-synthesized samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), respectively. From the results, it was found that the properties of the sample can be improved by tuning the Cu2+ concentration in the electrolyte, and the best sample was obtained with the Cu2+ concentration of 0.01 M. For the best sample, the CFTS thin films have single phase and good crystallinity with even particle size. By the addition of ascorbic acid, an effective way has been found to enhance the Fe content in the sample, and the reason for the Fe-poor phenomenon has also been explored.

Effect of sulfur concentration on structural, optical and electrical properties of Cu2FeSnS4 thin films for solar cells and photocatalysis applications

Quaternary chalcogenide Cu2FeSnS4 (CFTS) thin films were successfully elaborated by spray pyrolysis technique on glass substrates using different thiourea concentrations (4, 5, 6 and 7.10−2M) as sulfur source. The chemical composition, morphological, structural, optical and electrical properties were investigated using respectively dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements. XRD and Raman spectroscopy revealed that CFTS thin films synthesized at thiourea concentration [S] = 6.10−2M grows with a pure and good crystalline quality. CFTS thin layer crystallized into the stannite structure with the preferred orientation (112) plan. The average grain size reaches a maximum value about 41 nm at [S] = 6.10−2M. The obtained CFTS stoichiometric ratio was Cu:Fe:Sn:S = 2,25/1/0,91/4,08 which is close to the theoretical ratio 2:1:1:4. Optical properties present a high absorption coefficient value equal to 8 104 cm−1, with an estimated band gap value 1,05 eV. This work demonstrates also that electrical resistivity was about 0,46 Ω cm at room temperature and has been decreased to a minimum value of 0,014 at 80 °C. All these experimental results make sprayed CFTS thin film synthesized at [S] = 6.10−2 M as a promising absorber layers in solar devices. Methylene Blue dye under sun illumination has been used to test to photocatalytic activity of optimum CFTS thin film. A value of photo-degradation near 76% of MB dye has been obtained for 4 h duration. This result show that CFTS thin film synthesized at [S] = 6.10−2 M is a good candidate for photocatalysis applications.

Recent advances in synthesis of Cu2FeSnS4 materials for solar cell applications: A review

The earth-abundant Cu based multinary chalcogenides have great interest in the field of environmentally benign thin film solar cells. Recently, Cu2FeSnS4 (CFTS), one of the important Cu based chalcogenide has drawn prime attention in research and development due to their nontoxic and earth abundant constituent elements. The optical properties of CFTS make it a suitable candidate for thin film solar cells (TFSCs). This paper provides a review on the physical and chemical synthesis of CFTS nanoparticles and thin films and focuses the current status of CFTS based TFSCs. This article begins with a description of the crystal structure of CFTS, and then discussion on various solution and vacuum based techniques used to grow nanostructures and deposit compact thin films. Further, the review will summarize photovoltaic behavior of CFTS thin films. Finally, we discussed the challenges and scope and the perspectives for further developments in the existing research on CFTS based solar cells.

Growth and Characterization of the Evaporated Quaternary Absorber Cu2FeSnS4 for Solar Cell Applications

Cu2FeSnS4 (CFTS) was synthesized by direct fusion of high-purity elemental copper, iron, tin and sulfur. CFTS thin films were deposited on glass substrates heated by single source vacuum thermal evaporation, after which the obtained samples were annealed under a sulfur atmosphere in a sealed quartz tube at 400°C for 1 h in order to optimize the CFTS stannite phase. The substrate temperature was varied from room temperature to 200°C. The formation of a stannite structure with (112), (200) and (004) planes in the powder and thin films was confirmed using x-ray diffraction measurements and the crystallites were found to have a preferred orientation along the (112) direction. Optical measurements analysis showed that after the sulfurization process the layers have a relatively high absorption coefficient close to 105 cm−1 in the visible spectrum. The films show a direct optical band gap in the range 1.30–1.63 eV for substrate temperature varied from room temperature to 200°C. All samples revealed p-type conductivity as determined by the hot probe method.

Effect of thermal annealing on the structural and optical properties of Cu2FeSnS4 thin films grown by vacuum evaporation method

In this work, the effect of different types of thermal annealing on the properties of Cu2FeSnS4 (CFTS) thin films deposited by thermal evaporation at room temperature on glass substrate were investigated. CFTS powder was synthesized by direct melting of the constituent elements taken in stoichiometry compositions. The X-ray diffraction experimental data indicating that the Cu2FeSnS4 powder illustrating a stannite structure in space group I$$\bar {4}$$2m. From the XRD analysis we have found that the polycrystalline CFTS thin film was only obtained by thermal annealed in sulfur atmosphere under a high vacuum of 400 °C temperature during 2 h. Optical study reveals that the thin films have relatively high absorption coefficients (≈ 105cm−1) and the values of optical band gap energy ranged between 1.38 and 1.48 eV. Other optical parameters were evaluated according to the models of Wemple Di-Domenico and Spitzer-Fan. Finally, hot probe measurements of CFTS thin films reveal p-type conductivity.

Effect of the spraying temperatures and the sulfurization on the properties of the absorber Cu2FeSnS4 thin films in a solar cell

The quaternary Cu2FeSnS4 (CFTS) is regarded like the one of the semiconductors promoting as an effective photovoltaic absorber because of their earth-abundant and non-toxic elements. The thin films were elaborated by spray pyrolysis method deposited onto glass substrates at 370 °C for one hour with post-sulfurization treatment at 450 °C for 30 min. XRD spectra analysis showed that the CFTS thin films have tetragonal structure with a main peak corresponding to the direction (1 1 2). The Raman spectrum confirmed these results with an appearance of two main peaks corresponding to the CFTS situated at the positions 289 cm−1 and 318 cm−1. The CFTS films exhibit a homogeneous, rough and dense topography with a thickness of about 0.8 μm. The films of CFTS present a high absorption coefficient (≥105 cm−1) and the direct band gap energy is found to be 1.55 eV, which confirms their use as an absorber for solar cells.