Quaternary Cu2ZnSnS4 Research Articles

Phase transformation of solution-based p-type Cu2ZnSnS4thin film: applicable for solar cell

In this present work, quaternary Cu2ZnSnS4 thin films were deposited on commercial glass substrates at room temperature by a novel solution growth dip coating technique. The influence of annealing temperature of the films at 300 °C in a hot air furnace without the presence of any inert gas, on structural, optical, and electrical properties was investigated and discussed. The structural analyses were analyzed by X-ray diffraction and Raman spectroscopy, whereas optical and electrical properties were analyzed by means of ultra violet infrared (UV-ViS/IR). The results analyzed showed that there exists a phase formation from orthorhombic to kesterite crystal structure with an increase in optical bandgap and an optical conductivity, with an increase in annealing temperature. The electrical conductivity was observed of the order of 10−6 ohm cm−1. Copyright © 2015 John Wiley & Sons, Ltd.

Quaternary semiconductor Cu2ZnSnS4 loaded with MoS2 as a co-catalyst for enhanced photo-catalytic activity

Quaternary Cu2ZnSnS4 (CZTS) loaded with 1% MoS2 shows excellent photo-catalytic activity for water oxidation, leading to efficient H2 generation (AQY 22.67%), as well as in the degradation of an organic pollutant.

Muonium states in Cu2ZnSnS4 solar cell material

We investigated bulk and thin-film samples of the quaternary p-type semiconductor Cu2ZnSnS4 (CZTS) by μSR, in order to characterize the existing muonium signals. We find that the majority of the implanted muons form a diamagnetic state broadened by an interaction with the Cu nuclear moments, which we interpret as Mu+ bound to sulphur. A paramagnetic fraction is also present at low temperatures and the ratio between the two muon charge states, Mu+ and Mu0, varies between 20 and 40% prior to the onset of muon diffusion, which occurs at around 150 K. The fraction of Mu0 is found to be sensitive to the defect content of the sample. The paramagnetic fraction has two different contributions and their origin is discussed and related with the muon role as a probe for charge carriers in the material.

A facile and scalable route to nano-crystallized kesterite Cu2ZnSnS4 fibers via electrospinning/sulfurization

In this work, we report facile route to quaternary kesterite Cu2ZnSnS4 (CZTS) microfibers through electrospinning method. Precursor fibers are electrospun from the solution composed of Cu(CH3COO)2, Zn(CH3COO)2, and SnCl4 as the solutes, ethylene glycol methyl ether as the solvent, and polyvinylpyrrolidone (PVP) as the plasticizer. CZTS fibers are obtained after annealing at 773K for 40min in a sulfur ambient. Characterization including scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra, confirm the formation of single-phased, well-crystallized CZTS fibers, with a band gap of about 1.48eV estimated from the optical absorption curve. In addition, the fiber growth mechanism is proposed to explain the spontaneous reaction and crystallization of CZTS, as confirmed by the thermodynamic calculations.

Cu2ZnSnS4 alloys synthesized from Cu2SnS3@ZnS nanoparticles via a facile hydrothermal approach

A facile and low-cost approach was developed to prepare high quality quaternary Cu2ZnSnS4(CZTS) alloys through the thermal treating of the core–shell Cu2SnS3@ZnS nanoparticles. The synthesis process of the core–shell structure involves a simple two-step hydrothermal route that starts from the well-dispersed ternary Cu2SnS3 core with the introduction of poly(vinylpyrrolidone) (PVP) in the reaction solution, and ended by the coated binary ZnS shell upon the adsorption of citrate groups onto the preformed cores. X-ray diffraction, Raman spectrum and UV–vis absorption spectrum confirmed the single-phase formation and the proper bandgap of 1.51eV for the CZTS alloys. This effective hydrothermal method can be readily applied for industrial production.

The synthesis of Cu2ZnSnS4 nanocrystals prepared by a facile calcination route in the atmosphere

In the present work, a novel and facile calcination route was developed for the synthesis of quaternary Cu2ZnSnS4 nanocrystals in the atmosphere for the first time. The as-synthesized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and UV–vis–IR spectrophotometer. The results showed that the as-synthesized nanocrystals had a kesterite structure, stoichiometric composition, irregularly spherical shape with size of around 10nm. Meanwhile, optical measurement showed that the nanocrystals had direct band gap energy of 1.4eV, which was near optimal value for efficient solar energy conversion in a single band gap device.

Fabrication of Cu<sub>2</sub>ZnSnS<sub>4</sub> Thin Films by Sputtering from a Single Quaternary Chalcogenide Compound

Cu2ZnSnS4thin films were fabricated by one-step RF magnetron sputtering of a single quaternary Cu2ZnSnS4(CZTS) chalcogenide target on Mo/soda lime glass substrate, followed by post sulfurization using S vapor obtained from elemental S powders. The films were thermally annealed in Ar atmosphere to improve the crytallinity. The sulfurization temperature was fixed at 550°C. Both as-deposited and post-sulfured samples are close to the stoichiometric composition, meanwhile without any second phase was detected by XRD. As-deposited film has a compact columnar grain characteristic. Although crystallinity was improved with increasing annealing time, this characteristic disappeared after post-sulfured.

Electronic and optical properties of substitutional V, Cr and Ir impurities in Cu2ZnSnS4

The substitution of cation atoms by V, Cr and Ir in the natural and synthetic quaternary Cu2ZnSnS4 semiconductor is analyzed using first-principles methods. In most of the substitutions, the electronic structure of these modified CZTS is characterized for intermediate bands with different occupation and position within of the energy band gap. A study of the symmetry and composition of these intermediate bands is carried out for all substitutions.These bands permit additional photon absorption and emission channels depending on their occupation. The optical properties are obtained and analyzed. The absorption coefficients are split into contributions from the different absorption channels and from the inter- and intra-atomic components. The sub bandgap transitions are significant in many cases because the anion states contribute to the valence, conduction and intermediates bands. These properties could therefore be used for novel optoelectronic devices.

Cu2ZnSn(S,Se)4 solar cells from inks of heterogeneous Cu–Zn–Sn–S nanocrystals

The solution-based synthesis of quaternary Cu2ZnSnS4 (CZTS) nanocrystals and further processing into a homogeneous photovoltaic absorber film prove challenging due to the stability of binary and ternary chalcogenide compounds comprised of Cu, Zn, and Sn cations. In this contribution, CZTS nanocrystals are synthesized according to a previously reported synthesis recipe yielding devices with reported efficiencies as high as 7.2%. The particles are separated by size into two populations exhibiting size-correlated composition variations. This observation highlights the challenges in synthesizing quaternary CZTS nanoparticles with interparticle composition uniformity. Films of particles from each population are sintered in a selenium atmosphere and found to exhibit a notable degree of phase segregation in the final film, while a mixture of particles from both populations converts into a relatively homogeneous film upon selenization. Devices fabricated from the two particle populations separately as well as the mixture of particles exhibit varying degrees of performance, with the mixed particle cells achieving total area efficiencies as high as 7.9%. A modified synthesis recipe producing CZTS particles with narrower composition variations is shown to produce devices with improved efficiencies up to 8.4%. Preliminary conclusions regarding the effect of nanocrystal heterogeneity on film sintering and device performance are presented.

Size and shape controlled hydrothermal synthesis of kesterite Cu2ZnSnS4 nanocrystals

Quaternary kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) have been synthesized using a simple, size and shape tunable, and low-cost hydrothermal technique without using toxic chemicals.

Electrochemical Deposition of CZTS Thin Films on Flexible Substrate

In this work, we report some preliminary results concerning the fabrication of quaternary semiconductor Cu2ZnSnS4 (CZTS) thin films on a flexible substrate through the simultaneous electrodeposition of elements having different standard electrochemical potentials. CZTS thin films were obtained by potentiostatic deposition from aqueous baths at room temperature and under N2 atmosphere, varying bath composition. Chemical composition and structure of the electrodeposited films were evaluated by EDS, SEM, RAMAN and XRD. Preliminary results on the photoelectrochemical behaviour of the films will be also presented.

Thermo-physical properties of Cu2ZnSnS4 single crystal

The thermo-physical properties of quaternary compound Cu2ZnSnS4 (CZTS) have been evaluated from high-quality single crystals grown by the solution method. The Debye temperature, one of the important properties, was determined from the measured heat capacity value below 7K using the Debye function. The experimental Debye temperature is 302K, which is a reference value for the thermo-physical understanding of CZTS. The present result can be used to stimulate future experimental and theoretical work.

Ionization energies of amphoteric-doped Cu2ZnSnS4: Photovoltaic application

The substitution of Cu, Sn or Zn in the quaternary Cu2ZnSnS4 semiconductor by impurities that introduce intermediate states in the energy bandgap could have important implications either for photovoltaic or spintronic applications. This allows more generation–recombination channels than for the host semiconductor. We explore and discuss this possibility by obtaining the ionization energies from total energy first-principles calculations. The three substitutions of Cu, Sn and Zn by impurities are analyzed. From these results we have found that several impurities have an amphoteric behavior with the donor and acceptor energies in the energy bandgap. In order to analyze the role of the ionization energies in both the radiative and non-radiative processes, the host energy bandgap and the acceptor and the donor energies have been obtained as a function of the inward and outward impurity-S displacements. We carried out the analysis for both the natural and synthetic CZTS. The results show that the ionization energies are similar, whereas the energy band gaps are different.

Mechanistic aspects of preheating effects of electrodeposited metallic precursors on structural and photovoltaic properties of Cu2ZnSnS4 thin films

Effects of 350°C preheating of electrochemically stacked Cu–Sn–Zn layers in an inert atmosphere on structural and morphological properties of quaternary kesterite Cu2ZnSnS4 (CZTS) films obtained by sulfurization of the metallic layers were investigated. When the CZTS film was fabricated without the 350°C preheating, the film contained a secondary Cu2SnS3 phase and other impurities. The CZTS film also showed poor adhesion to the bottom molybdenum (Mo) substrate with many crevices and voids in the film; a very thick MoS2 layer was formed at the top part of the Mo layer. These structural failures of the CZTS film were significantly reduced when the metallic precursor was preheated at 350°C before sulfurization for 20min: the CZTS film thus-obtained exhibited no secondary phases, good adhesion to the bottom Mo layer, flat and densely packed surface morphology, no appreciable crevices or voids, and formation of a relatively thin MoS2 layer. Based on results of studies on structural transformations during 350°C preheating and successive sulfurization, such differences in properties of resulting CZTS films are attributed to differences in formation pathways. Moreover, since 350°C preheating for a longer duration was found to be detrimental for the properties of resulting CZTS films, there should be an optimum duration of preheating to achieve a good CZTS film for solar cell application. As expected from these properties, the solar cell with an Al:ZnO/CdS/CZTS/Mo structure derived from the metallic precursor preheated at 350°C for 20min showed the best conversion efficiency of 5.6%.

Re-Crystallization of CZTS Solar Cell Materials Prepared by Galvanostat Electro-Deposition

Quaternary Cu2ZnSnS4 (CZTS) films were successfully obtained on Mo/(soda lime glass) substrates by one-step electro-deposition. The process was more efficient than other electro-deposit processes. Electrolytic aqueous was prepared using CuSO4, ZnSO4, SnSO4 and Na2S2O3 mixing solution. A galvanostat was applied for the deposition using a double-electrode scheme. The as-deposited CZTS was re-crystallized and then treated with sulfurization. Kesterite-type CZTS with nano-particle sizes ~17 nm on Mo/SLG were identified by x-ray diffraction (XRD). Different CZTS granules with sizes of 0.5 ~ 5 um were aggregated on surface morphologies as analyzed by scanning electron microscopy (SEM). The CZTS crystallinity was improved through the re-crystallization process. The absorption coefficients are over 1x104 cm-1 in the visible range. The spectrum of square absorption coefficient versus photon energy spectra depicts that the obtained CZTS has a band gap energy of ~1.25 eV. The optical band gap depicts that the obtained CZTS is suitable for thin film solar cell application.

Correlation between intrinsic defects and electrical properties in the high-quality Cu2ZnSnS4 single crystal

Temperature dependent Hall effect measurements from 20 to 300 K have been performed on the quaternary compounds Cu2ZnSnS4 (CZTS) single crystals. The conductivity mechanisms can be described by a two-path system using Mott variable range hopping and typical thermal activation conduction. The center level of the acceptor band is 132 meV above the valence band maximum and is of width 40 meV. A correlation between the activation energy and acceptor concentration in CZTS is observed.

Directly electrospinning growth of single crystal Cu2ZnSnS4 nanowires film for high performance thin film solar cell

Quaternary kesterite-type Cu2ZnSnS4 nanowires can be used as absorbing materials for thin film solar cells. The structural, morphological, compositional, and optical properties of the CZTS nanowires have been studied using X-ray diffraction (XRD), UV–vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorption techniques respectively. The Cu2ZnSnS4 nanowires, fabricated by electrospinning process and sintered at 600 °C in Argon atmosphere, the cells exhibits a power conversion efficiency of 6.18% under AM 1.5 solar irradiation in the thin film solar cells. This study suggests that the optimized Cu2ZnSnS4 composite nanowire is a promising absorbing material for high performance solar cells.

Synthesis of Cu2ZnSnS4 thin films by dip-coating method without sulphurization

Quaternary Cu2ZnSnS4 (CZTS) thin films, a promising absorber material for solar cells has been successfully deposited on glass substrates by cost effective simple dip-coating method without using either polluting chemicals or expensive vacuum facilities. X-ray diffraction pattern reveals the formation of CZTS films with tetragonal type kesterite structure. The Raman spectra of the prepared films exhibited resonance peaks corresponding to the CZTS phase. The scanning electron microscopic image shows the formation of films with smooth surface. The surface topography studied using atomic force microscope gives an rms roughness of 1.6 nm. The Hall effect studies indicate that the prepared films are p-type with a carrier concentration of 4.77 × 1020 cm−3. The energy dispersive X-ray analysis result indicate the presence of Cu, Zn, Sn and S in the film. The absorption coefficient was found to be the order of 104 cm−1 and the band gap has been found to be 1.5 eV.

Cellulose acetate assisted synthesis and characterization of kesterite quaternary semiconductor Cu2ZnSnS4 mesoporous fibers by an electrospinning process

Quaternary kesterite-type Cu2ZnSnS4 (CZTS) mesoporous fibers for low-cost thin film solar cells were successfully synthesized by a relatively simple electrospinning process. Semiconductor CZTS mesoporous fibers were obtained from CA/CZTS precursor after annealing treatment at 450 °C for 3 h. CZTS mesoporous fibers were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The optical properties of the CZTS mesoporous fibers were also recorded by UV-vis absorption spectroscopy. The results showed that the synthesized CZTS mesoporous fibers had a single phase, good crystallinity and a stoichiometric composition. Moreover, the prepared mesoporous fibers had a size ranging from 200–500 nm and a band gap of 1.46 eV, which demonstrates that they are suitable for use in a thin film solar cell light absorption material.

Hierarchical porous Cu2ZnSnS4 films for high-capacity reversible lithium storage applications

Sulphide-based materials have attracted much attention as high performance electrode candidates for lithium batteries. However, a serious irreversible capacity decay after the first cycle of such materials inhibits their widespread applications in rechargeable batteries. In this work, a highly porous (3D) quaternary Cu2ZnSnS4 (CZTS) film was synthesized through a facile solution pyrolysis method. An initial discharge capacity of 1154 mA h g−1 and a stabilised value of about 680 mA h g−1 after 40 cycles at a current rate of 100 mA g−1 were achieved. Such significantly improved capacity and stability (especially for the first several cycles) indicate the great advantages of this 3D nanostructured CZTS electrode for advanced secondary lithium batteries.