Deposited CZTS Films Research Articles

Effect of growth temperature on the physical properties of Spray pyrolysis deposited CZTS films

Cu2ZnSnS4 (CZTS) functional thin films have been successfully synthesized using the spray pyrolysis method in a single deposition process and under atmospheric pressure. The samples have been deposited on glass substrates under different growth temperatures ranging from 350 °C to 450 °C. The solution has been prepared using Copper chloride dihydrate, Zinc chloride, Tin chloride dihydrate, and Thiourea as Copper, Zinc, Tin and Sulfur sources respectively. The structural, optical, morphological and electrical properties of CZTS films have been investigated. X-ray diffraction (XRD) and Raman spectroscopy have confirmed the kesterite structure of all samples without any secondary phase. The surface morphology and topography of the samples have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Data from UV–Vis spectroscopy analysis and Hall effect measurement showed that CZTS films elaborated at 400 °C have an optimum band gap (Eg = 1.5 eV), low resistivity (1.7239 × 10−2 Ω.cm), and high conductivity (58.00 (Ω.cm)−1).

Spray-deposited kesterite Cu2ZnSnS4 (CZTS): Optical, structural, and electrical investigations for solar cell applications

Kesterite Cu2ZnSnS4 (CZTS)-based solar devices have become a popular alternative to copper indium gallium selenide (CIGS) due to its outstanding properties such as high efficiency, non-toxicity, cost-effectiveness, suitable optoelectrical properties, and earth-abundancy. In this study, we directly fabricated CZTS films via a single-step spray pyrolysis technique, in contrast to conventional techniques where post sulfurization is required. The spray deposited CZTS films are investigated for their optical, structural, and electrical properties. The X-ray diffraction (XRD) and Raman analysis study revealed the synthesis of the phase-pure kesterite CZTS films without impurity phases. Large crystallites of CZTS are obtained at a deposition temperature of 400 °C, exhibiting a porous granular morphology with different grain sizes upon temperature variation. The size-dependent optical properties revealed that the CZTS films exhibited admirable visible light absorption of 105 cm−1 and an electronic bandgap ranging between 1.42 and 1.58 eV. The minimum dielectric loss obtained for optimized CZTS due to fewer intrinsic defects confirmed the materials’ applicability. Thus, the study provides a simple, viable route to fabricate CZTS without post-treatment to build affordable solar cells.

Properties of thermally evaporated CZTS thin films and numerical simulation of earth abundant and non toxic CZTS/Zn(S,O) based solar cells

Earth abundant Cu2ZnSnS4 (CZTS) films were grown by thermal evaporation technique onto non heated substrates. As deposited CZTS films were annealed under two different atmospheres: (1) vaccum annealing atmosphere and (2) sulfur annealing atmosphere followed by vacuum annealing. The samples were analyzed for their microstructural, electrical and optical properties before and after annealing. X-Ray Diffraction (XRD) analysis revealed that the as deposited film was amorphous whereas the annealed ones were polycrystalline with a highly (1 1 2) orientation. Raman spectroscopy confirmed the phase purity of annealed CZTS films. Both annealing atmospheres were found to decrease the band gap energy and the resistivity of the samples. All films exhibited p-type electrical conductivity. Numerical simulation of earth abundant CZTS thin film solar cells with non toxic Zn(S,O) buffer layer was performed by Solar Cell Capacitance Simulator (SCAPS-1D) using the experimental results obtained for CZTS and Zn(S,O) films. Zn(S,O) was used to substitute toxic CdS in earth-abundant Cd-free CZTS solar cells. A maximum conversion efficiency of 12.60% was obtained for Mo/p-Cu2ZnSnS4/n-Zn(S,O)/i-ZnO/n-ZnO:Al structure with CZTS film annealed under sulfur annealing atmosphere followed by vacuum annealing.

Structure, morphology and optical parameters of spray deposited CZTS thin films for solar cell applications

Objectives: To develop simple method for Cu2ZnSnS4 (CZTS) thin film deposition suitable for solar cell device application. Method: Cu2ZnSnS4 (CZTS) thin film was deposited by using simple chemical spray pyrolysis technique for substrate temperature (270±5) ◦C. Analytical reagent Grade 0.025 M Copper chloride (CuCl2), 0.0125 M zinc chloride (ZnCl2), 0.0125 M Tin chloride (SnCl4.5H2O) and 0.05 M Thiourea (SC (NH2)2) were used as sources of copper (cu+ ), zinc (Zn+), tin (Sn+ ) and sulfur (S- ) ions respectively. The structure, morphology and optical band gap of the film were investigated by using X-ray Diffractometer (XRD), Scanning Electron Micrograph (SEM) and UV-Visible spectroscopy respectively. Energy dispersive X-ray Analysis (EDX) was used for elemental analysis of deposited CZTS film. Findings: The XRD spectra showed that CZTS film exhibit polycrystalline tetragonal crystal structure with preferential orientation along (112) plane. The crystallite size calculated using full width at half maximum (FWHM) of (112) peak was to be 36.82 nm. SEM image revealed that film composed of regular arrangement of spherical granules of average size 1.61 µm. The purity of the CZTS phase was confirmed by elemental analysis. The calculated energy band gap (Eg) by using Tauc\'s plot was about 1.62 eV. The dc resistvity estimated by using IV characteristics of the CZTS film was to be 2.3× 10-2 Ω-cm. It is concluded that CZTS film prepared using present deposition technique can be used for solar cell device applications. Keywords: Chemical spray technique; CZTS Thin Films; band gap; structure of CZTS; electrical resistivity; elemental analysis

Investigations on copper zinc tin sulfide thin films grown through nebulizer assisted spray pyrolysis technique

An attempt is made in this work to synthesize the nontoxic Cu2ZnSnS4 (CZTS) thin film on FTO coated glass substrates through aerosol assisted nebulizer spray pyrolysis technique at different annealing temperatures for photovoltaic energy conversion. The deposited thin film is further used to form a heterojunction interface with a cadmium sulfide layer to fabricate a solar cell with Glass/FTO/CdS/CZTS/Ag superstrate structure to reveal its photovoltaic application. Various characterization techniques are utilized to study its inherent properties. X-ray diffraction (XRD) is employed to investigate the structural parameters such as crystallite size, microstrain and dislocation density which shows a preferential peak for (112) plane around 28.5° confirming the formation of kesterite CZTS. Raman measurements establish the peak for CZTS at 336 cm−1 and confirm the absence of parasitic secondary phases for an excitation wavelength of 488 nm. Scanning electron microscope and atomic force microscope used to examine the surface morphology and roughness of the films reveal a good surface morphology with a grain size of 555.9 nm and roughness of 123.7 nm for an annealing temperature of 350°C. The bandgap of the deposited CZTS films is found to be around 1.5 eV. The I-V characteristics of CZTS seem to be better for the 350°C annealed film. The performance of the optimized CZTS absorber layer is tested by forming a solar cell structure. The devised solar cell exhibited an open circuit voltage of 213 mV and a short circuit current density of 490 μA cm−2 with a conversion efficiency of 0.68% substantiating the usage of the prepared film as an absorber for photovoltaic conversion.

Facile designing and assessment of photovoltaic performance of hydrothermally grown kesterite Cu2ZnSnS4 thin films: Influence of deposition time

Herein, low cost precursor source Cu2ZnSnS4 (CZTS) nanocrystalline thin films at various reaction time were successfully synthesized via one step hydrothermal route. Hydrothermal route was employed to achieve control over the size and grain growth of CZTS films. As deposited CZTS films were analyzed for its optoelectronic, structural, morphological and electrochemical properties to investigate the effect of hydrothermal reaction time on growth and photovoltaic performance. The hydrothermal synthesis promoted to high absorption (104 cm−1) of the CZTS film with a decrease in optical band gap energy from 1.52 eV to 1.41 eV. Structural study revealed that, improved crystallinity with A1 mode of vibration for pure phase kesterite CZTS structure. Morphological transition was observed from nanograins to well grown and compact nanospheres. Compositional analysis illustrates, stoichiometric CZTS film formation with the desired valence state of Cu+, Zn2+, Sn4+ and S2− elements. Current density-voltage (J-V) measurement of FTO/CZTS/(0.3 M Eu3+/Eu2+)/Graphite cell configuration shows, highest photocurrent of 2.60 mA/cm2 and open circuit voltage of 754 mV was observed for CZTS4 sample with best photoconversion efficiency (η) 3.21% under illumination of 30 mW/cm2 light intensity. Electron impedance spectroscopy (EIS) showed that, generation of lower charge transfer resistance (Rct) with increase in reaction time.

Synthesis and surface characterization of electrodeposited quaternary chalcogenide $$\hbox {Cu}_{2}\hbox {Zn}_{x}\hbox {Sn}_{y}\hbox {S}_{1+x+2y}$$ thin film as transparent contact electrode

A low-cost technique, electrochemical deposition has been used to grow nanocrystalline quaternary Cu–Zn–Sn–S (CZTS) on indium tin oxide (ITO)-coated glass substrate. Effects of variations in deposition potentials and sulphur content on the chemical composition, optical, morphological, structural and electrical properties of the deposited films have been investigated. The morphologies showed and confirmed the results from XRD analysis that the films are of polycrystalline grains. Average interplanar spacing of the films is 3.376 A. The average film’s thickness as estimated from Rutherford back-scattered spectroscopy studies was 34 nm. The estimated stoichiometry was found to be that of $$\hbox {Cu}_{{{2}}}\hbox {ZnSnS}_{{{4}}}$$ tetragonal kesterite structure. Optical studies showed that the absorption characteristic of the deposited CZTS film across the wavelength region is significantly dependent on growth deposition potentials and electrolyte concentration. Estimated band gap is between 1.75 and 1.81 eV. The electrical studies showed that the deposited films exhibit ohmic characteristics. This study demonstrated successful deposition of tetragonal kesterite structures of CZTS using a two-electrode cell approach. It also revealed the novel route of growing CZTS thin film over the conventional three electrode cells.

Characteristics of kesterite CZTS thin films deposited by dip-coating technique for solar cells applications

In this work, we synthesis Cu2ZnSnS4 (CZTS) thin films by sol–gel method associated to dip-coating technique on the ordinary glass substrates. We investigated the effect of dip-coating speed on the structural, morphological, optical and electrical properties of films at various speeds 30, 40, 50 and 60 mm/min, respectively. The films have been characterized by different characterization techniques such as: X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), UV–Visible spectrophotometer and four point probe method. XRD spectra showed pure kesterite CZTS with a preferential orientation along (112) plane. Raman scattering measurement showed the peak at 332 cm−1 correspond to pure CZTS phase. XPS analysis confirmed the presence of Cu, Zn, Sn and S elements on the surface of deposited CZTS. SEM images showed an improvement in density and uniformity with increasing dip-coating speed. The band gap energy is decreased with increasing of dip-coating speed in the range of 1.38–1.45 eV. The electrical conductivity increased between 4.90 and 5.81 (Ω.cm)−1. These characteristics make the deposited CZTS film a suitable material as an absorber layer in photovoltaic devices.

Cu2ZnSnS4 Thin Films by Dip Coating from Metal-Thiourea Precursor Solution: Effect of Sulphurization Temperature on the Formation and Structural, Optical and Electrical Properties

A process for fabrication of kesterite-based Cu2ZnSnS4 (CZTS) thin films from metal-thiourea precursor solution by dip coating is described. As deposited CZTS films were sulphurized at different temperatures to study the effects of sulphurization temperature on structural, optical and electrical properties. Formation of tetragonal CZTS phase was confirmed by x-ray diffraction; phase purity of the films was further studied by Raman spectroscopy. The studies revealed phase pure crystal structure for the films sulphurized at 500°C and 550°C. Larger crystallite size was observed for films sulphurized at 550°C. Scanning electron microscopy studies showed uniform distribution of particles in the film sulphurized at 550°C, and the determined thickness of the films was ∼ 2 μm. Energy dispersive x-ray spectroscopy analysis revealed the effect of sulphurization temperature on elemental compositions of the films. Optical studies suggest that CZTS thin film sulphurized at 550°C has high absorption coefficient (105 cm−1) with an optical energy band gap of 1.43 eV. P-type nature of the films was confirmed from Hall Effect analysis. Carrier concentration, mobility and resistivity of the films sulphurized at 550°C were also calculated. The study optimized fabrication conditions for device quality CZTS thin films from metal-thiourea precursor solution by simple dip coating.

Intrinsic strain dependent redshift in optical band gap of Cu2ZnSnS4 nanostructured thin films

Single-phase Cu2ZnSnS4 (CZTS) thin films have been spray deposited on glass substrate, using uniform size oleic acid coated CZTS nanoparticles and the effect of heating temperature (75 °C to 300 °C) on the structural and optical properties have been investigated. X-ray diffraction results confirmed the formation of the single phase CZTS with a preferred orientation in (112) plane. The crystallite sizes of these films are ~7.0 ± 0.5 nm but the intrinsic strain present in the nanostructured films decreases from 9.1 × 10−3 to 1.3 × 10−3 with the increase of the heating temperature from room temperature to 300 °C. Optical band gap of the as deposited CZTS films is ~1.72 eV and it decreases to 1.45 eV for the CZTS films heated at 300 °C. The observed red shift in the band gap of CZTS films with the heating temperature has been attributed to a reduction in the intrinsic strain present in the film with the increase in the heating temperature.

Cost Effective Synthesis and Fabrication of Phase-Pure Kesterite Cu2-xZn1.3SnS4 P-type Absorber Layer Thin Films by Solvent Based Process Technique for Photovoltaic Solar Energy Applications

Solar has become one of the fastest growing renewable energy sources. With the push towards sustainability it is an excellent solution to resolve the issue of our diminishing finite resources. Alternative photovoltaic systems are of much importance to utilize solar energy efficiently. The Cu-chalcopyrite compounds CuInS2 and CuInSe2 and their alloys provide absorber material of high absorption coefficients of the order of 105 cm-1. Cu2ZnSnS4 (CZTS) is more promising material for photovoltaic applications as Zn and Sn are abundant materials of earth’s crust. Further, the preparation of CZTS-ink facilitates the production of flexible solar cells. The device can be designed with Al doped ZnO as the front contact, n-type window layer (e.g. intrinsic ZnO); an n-type thin film buffer layer (e.g. CdS) and a p-type CZTS absorber layer with Molybdenum (Mo) substrate as back contact. In this study, CZTS films were synthesized by a non-vaccum solvent based process technique from a molecular-ink using a non toxic eco-friendly solvent dimethyl sulfoxide (DMSO). The deposited CZTS films were optimized and characterized by XRD, UV-visible spectroscopy and SEM.

Cu2ZnSnS4 films with different preferred orientations prepared by pulsed DC magnetron sputtering from a quaternary ceramic target

Cu2ZnSnS4 (CZTS) films applicable to an absorber material in thin film solar cells were prepared at room temperature by pulsed DC magnetron sputtering from a CZTS ceramic target, and the effects of sputtering pressure on the phase, preferred orientation and composition of the deposited CZTS films were investigated. The results indicated that the dominant phase in the deposited films was Kesterite structure, only having the trace impurity phase of Cu2−xS. The preferred orientation was gradually converted from (2 2 0) to (1 1 2) with increasing sputtering pressure. Moreover, the composition of the deposited films was also affected by the sputtering pressures.

Microstructural, electrical and frequency-dependent properties of Au/p-Cu2ZnSnS4/n-GaN heterojunction

An Au/Cu2ZnSnS4 (CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, I-V and C-V measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82eV) compared to the Au/n-GaN SJ (0.69eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by I-V, Cheung’s and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density (NSS) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of NSS. Moreover, the capacitance-frequency (C-f) and conductance-frequency (G-f) characteristics of SJ and HJ are measured in the range of 1kHz–1MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the NSS estimated from C-f and G-f characteristics is lower compared to those estimated from I-V characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer.

The effect of additional sulfur on solution-processed pure sulfide Cu2ZnSnS4 solar cell absorber layers

ABSTRACTTo reduce the amount of chalcogen needed in the post-annealing process, we demonstrate significantly increased sulfur incorporation into pure sulfide CZTS films achieved by increasing the thiourea content of DMSO-based precursor solution. The increase of sulfur content was confirmed by thermogravimetric analyses (TGA). To understand how the elemental distribution across the CZTS layer is affected by extra thiourea, a systematic compositional study was carried out using X-ray photoelectron spectroscopy (XPS). XPS depth profiling reveals increased sulfur incorporation in the final CZTS films when more thiourea is added to the solution. The grain size was reduced slightly with increased sulfur content and the surface morphology was changed significantly. The effect on the surface of the CZTS film has been investigated using scanning electron microscopy (SEM), Raman spectroscopy, and XPS. External-quantum-efficiency (EQE) measurements with an electrolyte contact were used to investigate the optoelectronic properties of the deposited CZTS films.

Polyaniline/Cu2ZnSnS4 heterojunction based room temperature LPG sensor

Polyaniline/Cu2ZnSnS4 (PANI/CZTS) hetrojunction is fabricated by electrodepositing PANI on spray deposited CZTS film. The PANI/CZTS hetrojunction is characterized for its structural and surface morphological properties by X-ray diffractometer and scanning electron microscopy techniques. Forward biased PANI/CZTS heterojunction is used for detecting liquefied petroleum gas (LPG) at room temperature. The maximum LPG response of 79 % is observed for 780 ppm of LPG with 120 and 125 s response and recovery time periods, respectively with 92.6 % sensing stability.

Investigation of Annealing Conditions on Electrochemically Deposited CZTS Film on Flexible Molybdenum Foil

In this work, the electrodeposition of Cu2ZnSnS4 thin films on molybdenum thin foil was reported. In order to guarantee co-deposition of elements with different standard electrochemical potential, an aqueous electrolyte added with ligand agents was used. I addition, deposition parameters were carefully chosen, in order to ensure good quality and suitable composition of the films. The deposited films were sulfurized in controlled atmosphere at 580°C, scrutinizing the influence of the annealing conditions on the features of the films. Structure, morphology and composition were investigated by XRD SEM, EDS and Raman spectroscopy. Results reveal the growth of good quality films, with a uniform morphology and chemical composition suitable for solar cell application.

The effect of dextrin addition during Cu2ZnSnS4 thin film preparation by photochemical deposition

AbstractCu2ZnSnS4 (CZTS) thin films were prepared by annealing films of Cu2S, ZnS, and SnS2 precursors deposited on a soda‐lime glass substrate by photochemical deposition (PCD) from an aqueous solution containing CuSO4, ZnSO4, SnSO4, and Na2S2O3. This paper discusses the effect of adding dextrin as a titrant during the PCD preparation of CZTS thin films. We investigated the effects of dextrin addition on the surface morphology of the resulting films. The surfaces of films prepared with added dextrin were composed of uniformly sized grains. The results also demonstrate that the surface morphology of photochemically deposited CZTS films can be smooth if the proper additives are employed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Spray deposited copper zinc tin sulphide (Cu2ZnSnS4) film as a counter electrode in dye sensitized solar cells.

Stoichiometric thin films of Cu2ZnSnS4 (CZTS) were deposited by the spray technique on a FTO coated glass substrate, with post-annealing in a H2S environment to improve the film properties. CZTS films were used as a counter electrode (CE) in Dye-Sensitized Solar Cells (DSCs) with N719 dye and an iodine electrolyte. The DSC of 0.25 cm(2) area using a CE of CZTS film annealed in a H2S environment under AM 1.5G illumination (100 mW cm(-2)) exhibited a short circuit current density (JSC) = 18.63 mA cm(-2), an open circuit voltage (VOC) = 0.65 V and a fill factor (FF) = 0.53, resulting in an overall power conversion efficiency (PCE) = 6.4%. While the DSC using as deposited CZTS film as a CE showed the PCE = 3.7% with JSC = 13.38 mA cm(-2), VOC = 0.57 V and FF = 0.48. Thus, the spray deposited CZTS films can play an important role as a CE in the large area DSC fabrication.

Growth of Highly (112) Oriented Cu2ZnSnS4 Thin Film on Sapphire Substrate by Radio Frequency Magnetron Sputtering

ABSTRACTFor structural investigation, highly (112) oriented tetragonal Cu2ZnSnS4 (CZTS) thin films on hexagonal sapphire (0001) single crystal substrates were obtained by radio frequency (RF) magnetron sputtering. The influences of the deposition parameters, such as substrate temperature (Tsub) and working Ar pressure (PAr) on the chemical composition and structural properties of as deposited CZTS films were investigated. The film sputtered at 500°C has the only orientation of (112), also, it bears the best structural quality with pure CZTS phase and an estimated band gap of 1.51eV.

Synthesis and characterization of Cu 2ZnSnS 4 thin films grown by PLD: Solar cells

As-deposited and annealed Cu 2ZnSnS 4 (CZTS) thin films have been synthesized onto Mo coated glass substrates at different deposition times using pulsed laser deposition (PLD) technique. The effect of deposition time (film thickness) and annealing onto the structural, morphological, compositional and optical properties of CZTS thin films have been investigated. The polycrystalline CZTS thin films with tetragonal crystal structure have been observed from structural analysis. FESEM and AFM images show the smooth, uniform, homogeneous and densely packed grains and increase in the grain size after annealing. The internal quantitative analysis has been carried out by XPS study which confirms the stoichiometry of the films. The optical band gap of CZTS films grown by PLD is about 1.54 eV, which suggests that CZTS films can be useful as an absorber layer in thin film solar cells. Device performance for deposited CZTS films has been studied.