Cu2ZnSnS4 Films Research Articles

Synthesis and assessment of the Mo/MoO3/CZTS/Ag diode fabricated by one-pot hydrothermal route: impact of temperature

A facile one-step hydrothermal method was utilized to prepare Cu2ZnSnS4 film employing EDTA as a complexing agent. An effective Molybdenum oxide layer was also formed in the same approach for forming the Cu2ZnSnS4 film. The influence of preparation temperature on structural, morphology, and optical characteristics was studied. The formation of crystalline kesterite phase Cu2ZnSnS4 films with preferred orientation along the (112) plane was confirmed by X-ray diffraction and Raman spectroscopy, and it was also demonstrated that structure property changes with preparation temperatures: kesterite phase Cu2ZnSnS4 is formed at lower preparation temperatures and kesterite phase Cu2ZnSnS4 and Cu2S are formed with increasing preparation temperature. Also, Raman analysis confirmed the formation of a Molybdenum oxide layer on the Mo substrate. Field emission scanning electron microscopy revealed that surface morphology changes from leaves of trees to flake-flowers. According to UV-visible analysis, Cu2ZnSnS4 films exhibited high and wide absorbance spectra in the visible and infrared regions and a band gap between (1.67-1.9) eV. Photoluminescence analysis revealed emission peaks at (1.569, 1.55, and 1.56) eV for samples prepared at (160, 200, and 230)0C, respectively, which is very close to the band's gap of Cu2ZnSnS4. Finally, the electrical study of Mo/MoO3/CZTS/Ag junctions was performed by using current-voltage (I-V) measurement.

Influence of electrodeposited Cu2ZnSnS4 films for the reduction of 4-nitrophenol through electronic relay approach and serve as photoelectrode in PEC device

We explore the possibility of thin film Cu2ZnSnS4 (CZTS) as an effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in presence of NaBH4 through electronic relay process with the rate constant of 0.20 min−1, also as photoelectrode material for low-cost photoelectrochemical solar cells. Cu2ZnSnS4 thin films with thickness of ∼ 2 μm have been synthesized by an electrochemical approach. The electrochemical bath contained an aqueous solution of Cu(NO3)2·3H2O, Zn(NO3)2.6H₂O, SnC2O4 and Na2S2O3 with Citric acid as a chelating ligand at an optimum pH∼3.65. The morphology, composition, and optical properties were characterized by XRD, FE-SEM, HR-TEM, UV–Vis, FT-IR, and EPR analysis. The growth kinetics of CZTS have been invested with different time intervals, also changes of band gaps of deposited material have been noticed. Cyclic voltammetry of the electrode is done to predict the co-deposited system in the quaternary semiconductor in 0.1 M KCl as supporting electrolyte. The deposited Kesterite phase of CZTS has been systematically investigated to serve as an effective counter electrode material for photoelectrochemical (PEC) energy conversion in 0.5 M polysulfide (Na2Sx) redox couple which showed an efficiency of ∼ 4.395 %. The development of a facile and green chemical route for the preparation of a well crystallized and stable CZTS photoelectrode still remains a challenge.

Structural and optical properties of sulfurized Cu2ZnSnS4 films grown by one step method using calcined powders for electrical properties study of Al/p-Cu2ZnSnS4 Schottky diode

Structural and optical properties of sulfurized Cu2ZnSnS4 films grown by one step method using calcined powders for electrical properties study of Al/p-Cu2ZnSnS4 Schottky diode

Electrosprayed Cu2ZnSnS4 films from its nanoparticles for dye-sensitized solar cells

Electrosprayed Cu2ZnSnS4 films from its nanoparticles for dye-sensitized solar cells

Rapid Thermal Processing of Kesterite Thin Films

Multinary chalcogenides with Kesterite structure Cu2ZnSn(S,Se)4 (CZTSSe) are a prospective material base for the enhancement of the photovoltaics industry with abundant and environmentally friendly constituents and appropriate electro-physical properties for building highly efficient devices at a low cost with a short energy pay-back time. The actual record efficiency of 13.6%, which was reached recently, is far below the current isostructural chalcopyrite’s solar cells efficiency of near 24%. The main problems for future improvements are the defects in and stability of the Kesterite absorber itself and recombination losses at interfaces at the buffer and back contacts. Here, we present an investigation into the rapid thermal annealing (RTA) of as-electrodeposited thin films of Cu2ZnSnS4 (CZTS). The treatment was carried out in a cold wall tubular reactor in dynamic conditions with variations in the temperature, speed and time of the specific elements of the process. The effect of annealing was investigated by X-ray diffractometry, Raman scattering and Scanning Electron Microscopy (SEM). The phase composition of the films depending on treatment conditions was analyzed, showing that, in a slow, prolonged, high-temperature process, the low-temperature binaries react completely and only Kesterite and ZnS are left. In addition, structural investigations by XRD have shown a gradual decrease in crystallite sizes when the temperature level and duration of the high-temperature segment increases, and respectively increase in the strain due to the formation of the phases in non-equilibrium conditions. However, when the speed of dynamic segments in the process decreases, both the crystallite size and strain of the Kesterite non-monotonically decrease. The grain sizes of Kesterite, presented by SEM investigations, have been shown to increase when the temperature and the duration increase, while the speed decreases, except at higher temperatures of near 750 °C. The set of experiments, following a scrupulous analysis of Raman data, were shown to have the potential to elucidate a way to ensure the fine manipulation of the substitutional Cu/Zn defects in the structure of CZTS thin films, considering the dependences of the ratios of Q = I287/I303 and Q′ = I338/(I366 + I374) on the process variables. Qualitatively, it can be concluded that increases in the speed, duration and temperature of RTA lead to increases in the order of the structure, whereas, at higher temperatures of near 750 °C, these factors decrease.

Cu2ZnSnS4 films properties deposited by spray pyrolysis, subjected to a combined novel thermal treatment: CSS sulfurization and RTA post-treatment

CZTS films were obtained by spray pyrolysis, a low-cost technique implemented on an industrial scale. Sulfurization processes generally enhance CZTS properties for its use in solar cells; however, these require high temperatures and long times. In this work, CZTS films properties were studied after being subjected to a combined novel thermal treatment which involved two stages. Sulfur incorporation using close space sublimation technique (CSS) at a temperature (TCSS) in the 350–500 °C range for 60 s, and after a rapid thermal annealing post-treatment (RTA) at TRTA = 500 °C for 10 s, with a heating ramp of 5 °C/s under argon atmosphere. Morphological, structural, chemical composition, optical and electrical properties were studied for CZTS films subjected to CSS as CSS+RTA treatments for all TCSS values. From the results, efficient sulfur incorporation by CSS was obtained without substantial sulfur concentration loss after RTA treatment, associated with the short treatment time. In addition, significant enhancement of crystalline quality and electrical resistivity diminished of the films is obtained after the CSS+RTA process for all TCSS. CZTS films with the best properties are those obtained at TCSS of 400 °C, having Cu/(Zn+Sn) = 0.79 and Zn/Sn = 1.3 ratios, a direct bandgap value of 1.5 eV, and resistivity of 4 Ω-cm. These films can be candidates for their characteristics as an absorbent layer in solar cells.

Elaboration by spin coating and characterization of CZTS films

Thin films of Cu2ZnSnS4 (CZTS) were deposited by the sol-gel spin coating method from a non-aqueous solution containing different molarities of precursors, cupric chloride CuCl2 (2H2O) (2M), zinc chloride ZnCl2 (1M), stannic chloride SnCl2 (2H2O) (1M) and thiourea SC(NH2)2 (8M) dissolved in different volumes of solvents, methanol CH3OH and deionized water. A light-yellow solution was formed by thermal centrifugation at adjustable speeds for several minutes. Characterizations were carried out after deposition, drying and thermal annealing of these films. XRD spectra showed the formation of several peaks with one peak corresponding to the (112) directions illustrating the presence of kesterite. The gap energy was deduced 1.87 eV from the transmittance obtained by UV-Visible-NIR. The percentages of the different CZTS constituents by SEM were recorded. The thicknesses of the films obtained by profilometer are between 0.6 μm and 2 μm. The theoretical study and the results of the characterization can contribute to the realization of a CZTS active layer of a photovoltaic cell.

Deposition of Cu2ZnSnS4 layers by a novel single flash thermal evaporator from mixture element powder

This research studies the deposition ability of Cu2ZnSnS4 from a mixed element powder and without sulfurization by a novel flash single thermal evaporator technique. Elemental powders of the source, S, Sn, Zn, and Cu, are held in an evaporation boat to mix their vapour together and to evaporate the mixture at a high temperature. The effect of substrate temperature on the thin layers structure properties, optical properties and surface morphology is explored by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray, atomic force microscopy, and UV-Vis -NIR spectroscopy. Cu2ZnSnS4 films of kesterite structures are fabricated successfully at various substrate temperatures by this technique in one step without a sulfurization process. The substrate temperatures affect the composition and optical properties of the prepared layers by changing the concentration of elements and crystallinity. The layer prepared at 250°C exhibits an optimal stoichiometry and an optical bandgap value of 1.51 eV.

Constructing of Cu2ZnSnS4 thin films with enhanced optical properties for solar cell application

Thin films of Cu2ZnSnS4 (CZTS) were created utilizing the thermal evaporation method. For the (CZTS) nanoparticles, thermogravimetric analysis (TGA) was initially carried out. According to TGA analysis, different annealing temperatures (400, 450, 475, and 500 °C) were used to anneal the (CZTS) thin films. Investigations were done into how different annealing temperatures affected the structural, morphological, and optical characteristics of the CZTS films. The development of a thin CZTS crystal with a high-quality crystal structure has been demonstrated by XRD patterns and Raman spectra. Using Debye-Scherrer's equation, the crystallite size for CZTS thin films was determined to be between 8 and 69.9 nm. As the annealing temperature rises, crystallite size increases. Using a double-beam computer-controlled spectrophotometer with a 400–2500 nm wavelength range, the optical characteristics were examined. While the reflectance was discovered to increase with an increase in annealing temperature, the transmittance was found to decrease. Calculating the extinction coefficient and refractive index was done using Kramers-Kronig relations. Using Tauc's relation, the optical energy gap was estimated, and it was discovered that it shrank as annealing temperature was raised. The (CZTS) thin film that was annealed at 500 °C had the highest power conversion efficiency (PCE).

Non-stoichiometric effect and disorder in as-prepared Cu2ZnSnS4 films deposited at different temperatures by ultrasonic spray pyrolysis

A better understanding of its crystal structure, the formation of possible secondary phases, defects and Cu–Zn disorder effects is needed to improve the photovoltaic device performance of CZTS films. In this direction, the effect of deposition temperature on the structural inhomogeneities, such as secondary phases and Cu–Zn disorder, etc. as well as opto-electrical properties of CZTS were experimentally examined. For this purpose, a non-stoichiometric spraying solution was prepared and ultrasonically sprayed onto glass substrates at different deposition temperatures (350 °C, 400 °C, 450 °C, and 500 °C) to obtain CZTS films. Afterward, the structural, morphological, elemental, optical, and electrical properties of the deposited films were investigated in detail. By Lorentzian deconvolution of Raman spectra, 14 Raman vibrational modes were detected and seven of these were assigned to the secondary phases. Also, the ordered-kesterite phase (337 cm−1) of CZTS was found to crystallize along with the disordered-kesterite phase (329 cm−1) due to the disorder of the cation (Cu–Zn) sublattice. Optical band gaps for CZTS films decreased from 1.89 eV to 1.42 eV with increasing in deposition temperature. It was seen that not only optical band gaps but also Cu–Zn disorder and the amount of secondary phases in CZTS films tightly depend on the deposition temperature.

Ge incorporation in kesterite thin films by solution processing route: An in-depth study of structural and optoelectronic properties

Herein, we report a promising solution-processing method for the controlled incorporation of germanium (Ge) into Cu2ZnSnS4 (CZTS) films using a nontoxic molecular ink. The effect of Ge concentration on structural, optical, electrical and electronic properties of the films were systematically investigated. The successful Ge alloying in CZTS was confirmed by XRD analysis and exploring the sensitivity of Raman scattering. The as-synthesized Cu2ZnSn1-xGexS4 (CZTGS; x = 0, 0.1, 0.15, 0.2 and 0.25) films exhibit strong absorption in the visible region with the gradual increment in the band gap energy from 1.46 to 1.61 eV by increasing x from 0 to 0.25. A decrease in Urbach energy at higher [Ge]/[Sn + Ge] ratio supports the reduction of overall disorder into the system. The information about the correct oxidation states of the constituent elements and optimal chemical composition of the CZTGS films was obtained from X-ray photoelectron spectroscopy (XPS). The decrease in SnII/SnIV signal ratio with the increase in Ge further supports the suppression of deep-trap SnZn antisite defects. The XPS valence band spectra reveal that the position of valence band maximum ascended from 0.09 to 0.15 eV with increasing Ge content in the films. Several relevant optical constants were determined of the CZTGS films which are important for applications in solar cell devices as well as for simulation purpose.

Mapping the Energetics of Defect States in Cu2ZnSnS4 films and the Impact of Sb Doping.

The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor–acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.

Characterization of Cu2ZnSnS4 thin films prepared with and without thin Al2O3 barrier layer

We investigated the effect of thin Al2O3 barrier layer (∼20 nm) deposited by radio frequency magnetron sputtering technique on the structural, morphological, optical, and electrical properties of Cu2ZnSnS4 (CZTS) films. Major differences in the crystalline qualities of the films were not observed with the addition of the Al2O3 layer except for a small decrease in crystallite size. Raman spectra of the film with the Al2O3 layer exhibited the peaks belonging to ZnS and Cu2-xS secondary phases. X-ray photoelectron spectroscopy analysis showed that SO42- and CuSO4 compounds were formed on the surfaces of the films. The formation of the CuSO4 phase was associated with the bonding between CuO and S in an oxidized CZTS surface. The presence of the ZnS, Cu2-xS secondary phases, and CuSO4 on the surfaces of the films were also confirmed by scanning electron microscopy images. The film with the Al2O3 layer differed from the other films with its surface that have randomly distributed porous-structured agglomerations and a decrease in the ZnS secondary phases on its surface. All films exhibited different Na distributions in secondary ion mass spectroscopy depth profiles. The Al2O3 layer caused a slower gradient in Na diffusion with decreasing the accumulation of Na element at a distinct region. The activation energy for the thermally activated band conduction was calculated as 0.030 eV and attributed to the thermal release of the holes from the vacancy of copper (VCu) defect states. The results of temperature-dependent conductivity measurements indicated that there were different conduction mechanisms in the films.

Improvement of hetero-interface engineering by partial substitution of Zn in Cu2ZnSnS4-based solar cells

This paper investigates the effects of partial substitution of zinc (Zn) in pure sulfide kesterite (Cu2ZnSnS4) by cadmium (Cd) and manganese (Mn) incorporation. Thin films of Cu2ZnSnS4 (CZTS), Cu2Zn1–xCdxSnS4 (CCZTS) and Cu2Zn1–xMnxSnS4(CMZTS) were produced chemically. A comparison of pure CZTS with CCZTS and CMZTS was performed to study the influence of Cd and Mn incorporation on the morphology, structure, optical and electronic properties of the films. The results show an improvement of the morphology and an adjustment of the band gap and valence band position by partial substitution of Zn with Cd and Mn. In addition, for the first time, the band alignment at the absorber/buffer hetero-interface is studied with partial Zn substitution. Band alignments at the absorber/buffer hetero-interface were estimated by XPS and UV/Visible measurements. The results show a cliff-like CBO for CZTS/CdS heterojunction, a spike-like CBO for CCZTS/CdS and a near flat-band CBO for CMZTS/CdS heterojunction.

Study of Effect of Substrate Temperature on Structure, Morphology and optical Properties of Spray Deposited Cu2ZnSnS4 Nano Thin films.

Cu2ZnSnS4 (CZTS) films for different substrate temperatures were deposited by using simple chemical spray technique. Analytical reagent Grade; Copper chloride (CuCl2), Zinc chloride (ZnCl2), Tin chloride (SnCl4.5H2O) and thiourea (SC(NH2)2) were used as Cu+, Zn+, and Sn+ and ion sources respectively. A set of five CZTS films was deposited using five different substrate temperatures (175, 200, 250, 275, and 300 ). The structure, Morphology, Elemental analysis and optical properties of these films were studied using X-ray diffratometer (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and UV-Visible spectroscopy techniques respectively. The XRD spectra showed that all films are polycrystalline and exhibit kesterite tetragonal crystal structure with preferential orientation along (112) direction. The crstallinity was found increased with substrate temperature. The calculated crystallite size was increased with increase in substrate temperature. The surface morphology of CZTS films was improved with increase in substrate temperature. The film sample deposited for 275 represent excellent spherical granules CZTS crystals of increasing size from 640 nm to 1.8 μm arranged in regular fashion with some void spaces. The purity of the composition was investigated using Elemental analysis of the deposited films. The optical band gap was estimated using Tauc plots. The band gap obtained was to be in the range of 1.4 to 1.6 eV.

Properties of Cu2ZnSnS4 films obtained by sulfurization under different sulfur-vapor pressures in a sealed ambient

Thin-films of Cu2ZnSnS4 (CZTS), a promising photoabsorber for photovoltaics, were obtained by sulfurization of the precursor films at 550 °C in evacuated and sealed quartz ampoules under various partial pressures (22.3–232.5 kPa) of sulfur-vapor, and its effects on the morphological and optical properties were studied. The precursor films were obtained on the molybdenum (Mo) coated soda-lime glass substrate via solution-chemistry. The observed changes in the morphology have been explained based on the amount of CuS formed and its conversion to sulfur-poor Cu2S. A decrease in the grain size from 448 to 223 nm was observed with the increase in partial pressure of sulfur-vapor. The thickness of the molybdenum sulfide (MoS2) layer that forms at the CZTS – Mo interface during sulfurization, increased from 62 to 479 nm. The structural disorder, estimated using Raman spectroscopy, increased with the increase in the partial pressure of sulfur-vapor.

Synthesis and Characterization of Cu2ZnSnS4 Thin Films Obtained by Combined Magnetron Sputtering and Pulsed Laser Deposition.

Cu2ZnSnS4 (CZTS) is a complex quaternary material, and obtaining a single-phase CZTS with no secondary phases is known to be challenging and dependent on the production technique. This work involves the synthesis and characterization of CZTS absorber layers for solar cells. Thin films were deposited on Si and glass substrates by a combined magnetron sputtering (MS) and pulsed laser deposition (PLD) hybrid system, followed by annealing without and with sulfur powder at 500 °C under argon (Ar) flow. Three different Cu2S, SnS2, and ZnS targets were used each time, employing a different target for PLD and the two others for MS. The effect of the different target arrangements and the role of annealing and/or sulfurization treatment were investigated. The characterization of the absorber films was performed by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), Raman spectroscopy, scanning electron microscopy, and regular transmission spectroscopy. The film with ZnS deposited by PLD and SnS2 and Cu2S by MS was found to be the best for obtaining a single CZTS phase, with uniform surface morphology, a nearly stoichiometric composition, and an optimal band gap of 1.40 eV. These results show that a new method that combines the advantages of both MS and PLD techniques was successfully used to obtain single-phase Cu2ZnSnS4 films for solar cell applications.

Growth of Cu2ZnSnS4 thin films by hybrid chemical approach

Thin films of Cu2ZnSnS4 (CZTS), an emerging solar cell absorber layer, were prepared by a hybrid chemical process followed by annealing. In this process, two binary layers, SnS and ZnS were grown sequentially using chemical bath deposition method (CBD) onto soda-lime glass substrates. Subsequently the ZnS layer was partly converted into CuxS layer through an ion-exchange process by immersing the stack glass/SnS/ZnS in CuCl2 solution. The resulting stack, namely glass/SnS/ZnS/CuS, was annealed in sulphur atmosphere at 450 °C for an hour to promote inter-diffusion of the layers leading to the formation of CZTS film through the solid-state reaction path. The stack with a ZnS layer of 470 nm thick and 270 nm thick SnS led finally to the desired CZTS phase formation. XRD analysis of these films showed CZTS peaks which are close to the Cu2SnS3 (CTS) phase. Raman spectra recorded to distinguish CTS and CZTS phases showed modes at 291, 338 cm−1 corresponding to CZTS phase confirming its formation. The band gap of CZTS films is found to be 1.42 eV. The films were found to be p-type in nature. An attempt is made to fabricate heterojunction solar cell.

Investigation on in-situ thermal treatment of room-temperature pulsed laser deposition technique: How to improve Cu2ZnSnS4 films for photoelectric application without sulfurization

Is extra sulfurization an indispensable process for synthesizing quaternary chalcogenide? The answer is probably affirmative for most synthesismethods to suppress excessive sulfur vacancies. Pulsed laser deposition (PLD), an acknowledged technique for fabricating films with complex stoichiometry, is a greatalternative approach to prepare Cu2ZnSnS4 (CZTS) films. However, to prevent evaporative losses the deposition temperature (Tis) must be limited below 400 °C, which makes post-annealing process extremely requisite to improve metastable films. Herein we develop an in-situ thermal treatment technique in room-temperature (RT)-PLD-synthesis of CZTS films to evade extra sulfurization process. According to multi-peaks Gaussian fitting analysis, RT-PLD implementing optimized in-situ treatment can broaden solar absorption of CZTS films, potentially contributed by sub-bandgap absorption due to intrinsic natural-intermedium-band effects of I2-II-IV-VI4 chalcogenide compounds. Stabilized chronoamperometry characterization combined with quasi-stoichiometric ratio demonstrates that the RT-PLD technique can equivalently restrain sulfur vacancy generation even without sulfurization. Physical mechanisms associated to order–disorder transitions of polycrystal CZTS during in-situ treatment can interpret morphological “lumpy-smooth-vuggy” transformation along with Tis varied. Therefore, such proposed RT-PLD technique is applicable to prepare polynary compounds with volatile elements and complicated stoichiometry ratio.

Effect of thiourea on structure, morphology and optical properties of spray deposited CZTS thin films for solar cell applications

<p>Cu2ZnSnS4 (CZTS) films of different Thiorea (SC (NH2)2) molarity were deposited by using simple chemical spray technique at substrate temperature 275°C. Analytical reagent Grade Copper chloride (CuCl2), Zinc chloride (ZnCl2), Tin chloride (SnCl4.5H2O) were used as Cu+ , Zn+ , and Sn+ ion sources respectively and thiourea (SC(NH2)2) (0.02, 0.04 0.06 0.08, and 0.1 M) was used as a Sion source. A set of five CZTS films was deposited using five different molarity of thiourea. The structure, Morphology, Elemental analysis and optical properties of these films were studied using X-ray diffratometer (XRD), Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Analysis (EDX) and UV-Visible spectroscopy techniques respectively. The XRD spectra showed that all films are polycrystalline tetragonal structure with preferential orientation along (112) plane. The calculated crystallite size was increased with increase in thiourea concentration. Variations of optical band gap with thiourea molarity have been investigated using Tauc plots. SEM micrographs exhibits CZTS spherical granules regularly arranged with some void spaces. Purity of deposited films was investigated using EDX analysis. All the CZTS films exhibits higher absorption coefficient (𝛼 > 104) cm-1 and band gap in the reported range (1.2-1.53 eV) can be used as an absorber layer in solar cells.</p>