CZTS Research Articles

Comparison of electrical and photovoltaic parameters of the hetero-junction solar cells based on CZTS and CIGS ultrathin films

ABSTRACT Copper-Zinc-Tin-Sulphide (CZTS)/n-Si and Copper-Indium-Gallium-Selenide (CIGS)/n-Si hetero-junction solar cells have been manufactured using Pulse Laser Deposition (PLD) technique. Properties of both CZTS&CIGS ultrathin films have been produced in comparable thicknesses, analysed and compared to each other. CIGS ultrathin film has smaller main crystalline size but absorbs more light compared to CZTS. characteristics of CZTS/n-Si and CIGS/n-Si hetero-junctions have been obtained in the darkness and under light conditions. The ideality factor, barrier height, serial resistances of these hetero-junctions have been calculated by the traditional and Cheung-Cheung methods for the darkness. Although the serial resistance of CZTS hetero-junction has been found to be very low compared to CIGS hetero-junction, the efficiency and photocurrent of CZTS solar cell have been higher compared to those of CIGS solar cell. The photoelectric outputs of CZTS/n-Si and CIGS/n-Si cells have been studied using SCAPS-1D programme. We have found/concluded difference in characteristics between CZTS/n-Si and CIGS/n-Si structures.

Enhancement in efficiency of CZTS solar cell by using CZTSe BSF layer

Copper Zinc Tin Sulphide (CZTS) thin film solar cell achieved a great attention of researchers due to its optimum direct energy gap, higher absorption coefficient and good electronic properties. In this work, the CZTS/CdS based solar cell structure with and without back surface field (BSF) layer has been investigated numerically by usingSCAPS-1D. Firstly, a basic experimentally reported structure (FTO/ZnO/CdS/CZTS/Mo) without BSF layer is considered and replicated. Then, byinserting p-CZTSe material as BSF layer in between the absorber and back contact, a new device structure (FTO/ZnO/CdS/CZTS/CZTSe/Mo) has been proposed. The performance of both structures; with and without BSF layer, have been analyzed with respect to different layer parameters like: thickness, carrier concentration, and defect densities (Nt). A negative effect on cell performance has been observed with working temperature. From these analyses the optimum conversion efficiency of CZTS based PV cell without BSF layer has been found to be around 8.55% using CZTS absorber. The cell with CZTSe BSF layer (FTO/ZnO/CdS/CZTS/CZTSe/Mo) gives an overall conversion efficiency of 22.03%. The efficiency of both cells improved by replacing back contact metal with higher work function. This study gives the highest efficiency of about 29.86% for FTO/ZnO/CdS/CZTS/CZTSe/Pt structure. These simulation results could be an important guideline to a researcher for fabricating cost effective, non-toxic, and highly efficient CZTS solar cells.

Photocatalytic activities of hydrothermal synthesized copper zinc tin sulfide nanostructures

Photocatalytic activities of hydrothermal synthesized copper zinc tin sulfide nanostructures

Remarkable performance optimization of inverted p-i-n architecture perovskite solar cell with CZTS as hole transport material

Hole transport material (HTM) is a major component of perovskite solar cells (PSCs). PEDOT: PSS, an organic HTM, is widely used in inverted (p-i-n) PSCs. While PEDOT: PSS is unstable, expensive and it's acidic nature could deteriorate the absorber. Copper zinc tin sulphide (CZTS), an inorganic semiconductor can be used as HTM due to its properties such as low cost, ease of synthesis and high hole mobility. In this work, device simulation of inverted (p-i-n) PSC was performed with CZTS as HTM to exploit its maximum capability. Remarkable power conversion efficiency (PCE) of 25.43% was achieved after optimizing the performance. Device performance was strongly affected by thickness and electron affinity of HTM as well as diffusion length of carriers. PCE of real fabricated device was also found to be 9.72%. This work demonstrates CZTS is a promising candidate to replace PEDOT: PSS from both experimental and theoretical perspectives.

Kesterite Thin‐Film Solar Cell: Role of Grain Boundaries and Defects in Copper–Zinc–Tin–Sulfide and Copper–Zinc–Tin–Selenide

Kesterite materials, such as copper–zinc–tin–sulfide (CZTS) solar cell, have received considerable attention for low‐cost and high‐efficiency solar cells. However, the material suffers from poor quality of thin film during deposition, which, in turn, creates multiple grain boundaries along the layer. Consequently, a higher density of defects is randomly formed throughout the layer. Herein, the impact of different loss mechanisms on solar cell performance is analyzed. Numerical investigation on the influence of different loss mechanisms such as radiative recombination and recombination through traps and defects on the performance of the device is presented. A remarkable efficiency decrement of 10% in the devices is found due to the presence of defects and grain boundaries.

Boosting the Efficiency of CZTS/Si Tandem Solar Cells Using In2O3 Layer in CZTS Top Cell

AbstractWhile single‐junction solar cells may be capable of attaining AM1.5 theoretical efficiency of 33.16%, infinite multijunction (MJ, Tandem) solar cells will have a limiting efficiency of 86.8%. Tandem solar cells based on crystalline silicon (c‐Si) bottom cells are therefore attracting great interest. An interesting candidate for the top cell absorber is represented by copper zinc tin sulfide Cu2ZnSnS4 (CZTS). In this work, the CZTS/Si tandem solar cell is optimized by using indium oxide / Cadmium sulfide (In2O3/CdS) hybrid buffer. This present work reports CZTS/Si solar cell with an open‐circuit voltage VOC of over 0.942 V and a JSC of 34.7 mA cm−² by adding In2O3 layer in the CZTS top cell. The added In2O3 layer has a thickness of 0.022 µm and is n‐doped with a concentration of 1e20 cm−3. Compared with a CZTS/Si in which the hybrid buffer is of CdS, the efficiency is increased from 13.5% to 28.4%. These hybrid In2O3/CdS buffers provide a promising way to reduce the VOC deficit and further boost the efficiency of CZTS/Si solar cells.

Copper Zinc Tin Sulfide Anode Materials for Lithium-Ion Batteries at Low Temperature

Developing novel materials is crucial to overcoming the performance degradation of lithium-ion batteries (LIBs) for low-temperature applications. In this work, we demonstrate a novel copper zinc tin sulfide (Cu2ZnSnS4, CZTS) thin film with nanowalls structure as the anode material in thin-film LIBs for low-temperature applications. The quaternary CZTS synthesized by a simple hydrothermal method shows a higher reversible capacity of 475 mAh g–1 after 200 cycles at −10 °C with the EC/DEC/DMC-based electrolyte in comparison with the graphite electrode (110 mAh g–1 after 100 cycles at −10 °C). The effects of temperature and electrolyte systems including EC/DEC- and EC/DEC/DMC-based electrolytes on the cycling performance are studied. The faster Li-ion transport in the electrolyte–electrode interface of the CZTS anode material is obtained in the EC/DEC/DMC-based electrolyte at −10 °C. In addition, the depth-profiling XPS results of the CZTS anode reveal that a solid electrolyte interphase (SEI) layer with less carbon content is formed in the EC/DEC/DMC-based electrolyte likely associated with the interfacial stability at low temperature. The enhanced cycling performance of CZTS could be attributed to its improved interfacial stability and Li+ diffusion, along with the formation of an interconnected active material architecture at low temperature.

Suitable Top Cell Partners for Copper Indium Gallium Selenide‐Based Tandem Solar Cells to Achieve >30% Efficiency

A four‐terminal tandem structure based on the copper indium gallium selenide (CIGS) solar cell is a viable approach to achieve high efficiency. For this purpose, a dual‐junction configuration, consisting of the experimental CIGS cell with a record efficiency of 23.35% as the bottom cell and wide bandgap thin‐film solar absorbers as the top cell, is evaluated by modeling. Herein, the effects of luminescence efficiency, optical absorption, bandgap, thickness, and light trapping of the top cell on the designed tandem performance are investigated. The results show that the optimum bandgap and the thickness of the absorber layer for the top cell are between 1.7 and 2 eV and 0.5 μm, respectively. Light trapping for less than 1 μm‐thick top cell has a strong impact on cell performance. The analytical model for the tandem solar cell is provided to recognize the suitable materials as the partner for the CIGS cell. The analysis shows that the gallium arsenide (GaAs), copper zinc tin sulfide (CZTS), cadmium telluride (CdTe), and copper gallium selenide (CGS) thin‐film solar cells can be considered suitable top cells to achieve a tandem cell with more than 30% efficiency. The Al0.31Ga0.69As/CIGS tandem solar cells with 35.9% efficiency are also proposed.

Electrical, Optical, and Reliability Analysis of QD-Embedded Kesterite Solar Cell

Quantum engineering in kesterite solar cells reveals a blending advancement keeping in mind that copper–zinc–tin–sulfide (CZTS)-based material requires high-research implementation as a replacement for CIGS materials. In this article, a quantum-dot-embedded kesterite solar cell is proposed, in which CZTS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Se}1-_{x}$ </tex-math></inline-formula> and CZTS are taken as dot and barrier, respectively, with different sulfur (S) and selenium (Se) content. Focus is given on the incorporation of quantum dots (QDs) and a detailed investigation is carried out through optical and electrical performance, which shows the uniqueness of this study. Quantum efficiency of the solar cell with separate internal and external absorption is also investigated. Different issues on carrier propagation, recombination, and collection are emphasized to highlight the effect of carrier quantization in material. The reliability analysis of the solar cell is also a new scope to investigate the trap-assisted recombination. The detail analysis and remarkable efficiency may bring a new path for next-generation solar cells.

Solution‐Processed Semitransparent CZTS Thin‐Film Solar Cells via Cation Substitution and Rapid Thermal Annealing

Semitransparent solar cells are able to capitalize on land scarcity in urban environments by co‐opting windows and glass structures as power generators, thereby expanding the capacity of photovoltaics to meet energy needs. To be successful, devices must be efficient, possess good visual transparency, long‐term stability, and low cost. Copper zinc tin sulfide is a promising thin‐film material that consists of earth‐abundant elements. For optical transparency, the usual molybdenum back contact is replaced with a transparent conducting oxide (TCO). However, due to subsequent high‐temperature annealing, the TCO degrades, losing conductivity, or forms a poor interface with CZTS. Lower temperatures mitigate this issue but hinder grain growth in CZTS films. Herein, cadmium substitution and silver and sodium doping are used to aid grain growth and improve film quality at lower annealing temperatures. Thin molybdenum is sputtered on TCO to help improve the interface transition postannealing by conversion to MoS2. Rapid thermal processing is used to minimize high‐temperature exposure time to preserve the TCO. With these methods, a semitransparent device with a front illumination efficiency of 2.96% is demonstrated.

Phase evolution during annealing of low-temperature co-evaporated precursors for CZTSe solar cell absorbers

Systematic investigations into the phase evolution during reactive annealing of copper–zinc–tin–selenide (CZTSe) precursors for the fabrication of kesterite solar cell absorber layers have been paramount in understanding and suppressing the formation of secondary phases that deteriorate device performance. In this study, the phase evolution during annealing of low-temperature co-evaporated CZTSe precursors is investigated. A detailed analysis of films selenized at different temperatures is used to reveal the possible reaction pathway of CZTSe formation. Utilizing a combination of x-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy, it is shown that CZTSe formation starts by Cu out-diffusion to the surface and Cu–Se phase formation at a temperature of 350 °C. An intimate mixing of binaries and ternaries during low-temperature selenization is observed. On the contrary, only binaries are observed at high-temperature selenization. This suggests that the CZTSe formation pathway involves reaction schemes where (i) a competition between binary and ternary phases dominates at low-temperature and (ii) binary reactions dominate the process at high temperatures. However, the number of binary phases decreases with increasing selenization temperature until they become undetectable by XRD and Raman spectroscopy at a temperature of 540 °C (selenization time 10 min). Utilizing the presented selenization conditions, prototype solar cells with an efficiency of up to 7.5%, an open-circuit voltage of 407 mV, and a fill factor of 59%, could be demonstrated. The temperature-dependent current density–voltage characteristics indicate that the performance of the prototype devices is limited by bulk Schottky–Read–Hall recombination.

Electronics of Anion Hot Injection-Synthesized Te-Functionalized Kesterite Nanomaterial.

Metal chalcogenides such as copper zinc tin sulfide (CZTS) have been intensively studied as potential photovoltaic cell materials, but their viability have been marred by crystal defects and low open circuit potential (Voc) deficit, which affected their energy conversion efficiency. Strategies to improve on the properties of this material such as alloying with other elements have been explored and have yielded promising results. Here, we report the synthesis of CZTS and the partial substitution of S with Te via anion hot injection synthesis method to form a solid solution of a novel kesterite nanomaterial, namely, copper zinc tin sulfide telluride (CZTSTe). Particle-size analyzed via small angle X-ray scattering spectroscopy (SAXS) confirmed that CZTS and CZTSTe materials are nanostructured. Crystal planes values of 112, 200, 220 and 312 corresponding to the kesterite phase with tetragonal modification were revealed by the X-ray diffraction (XRD) spectroscopic analysis of CZTS and CZTSTe. The Raman spectroscopy confirmed the shifts at 281 cm−1 and 347 cm−1 for CZTS, and 124 cm−1, 149 cm−1 and 318 cm−1 for CZTSTe. High degradation rate and the production of hot electrons are very detrimental to the lifespan of photovoltaic cell (PVC) devices, and thus it is important to have PVC absorber layer materials that are thermally stable. Thermogravimetric analysis (TGA) analysis indicated a 10% improvement in the thermal stability of CZTSTe compared to CZTS at 650 °C. With improved electrical conductivity, low charge transfer resistance (Rct) and absorption in the visible region with a low bandgap energy (Eg) of 1.54 eV, the novel CZTSTe nanomaterials displayed favorable properties for photovoltaics application.

A Review of CZTS Thin Film Solar Cell Technology

Copper Zinc Tin Sulfide (CZTS) solar cells have recently attracted attention as a potential low-cost earth abundant replacement for CIGS cells. This is due to their constituent’s Zn and Sn are non-toxic and earth-abundant compare to the elements of In and Ga in CIGS. Thus, aiming to analyse solar cells free from the environmental contaminant, CZTS is viewed as a potential candidate as the absorber for the next generation thin film solar cells. However, the conversion efficiency of CZTS based solar cells reported which is relatively low (highest conversion efficiency recorded is 12.5%) from the theoretical conversion efficiency limit of 32.2%. This is due to the low fill factor (FF), open circuit voltage (Voc) and current density (Jsc). In this study analysis of the different CZTS based solar cells and its synthesis methods will be reviewed. The effect of the compositional change and various structure in the CZTS, different buffer layers with their interfaces are thoroughly studied. The challenges regarding improving the conversion efficiency of CZTS solar cells and their future in the thin film solar cell application are discussed.

Deposition of CZTS|ZnO Hetero-Junction Using SILAR and Spray Pyrolysis

Copper zinc tin sulphide (CZTS) thin films have been deposited on glass substrate at 323 ± 5 K using sequential ionic layer adsorption reaction (SILAR). The number of SILAR cycles required for optimum crystalline quality CZTS thin films was optimized. The as-deposited CZTS thin films showed kesterite crystalline structure with preferential orientation along (103) plane. Structural, optical, electrical, and morphological properties of the films changed when the as-prepared films were subjected to annealing in a vacuum chamber maintained at 3 × 10–4 Torr at temperatures of 473, 573, and 673 K. Film resistivity was found to decrease exponentially as the annealing temperature was increased. We have achieved a resistivity of 4.4 × 10–4 Ω m for the as-prepared thin film, which is lowest among SILAR-grown films at temperature lower than 373 K without any post-deposition processing. A superstrate-type p–n junction was fabricated by growing nano-structured zinc oxide (ZnO) on top of the glass|CZTS structure using chemical spray pyrolysis technique. The photosensitivity of the p–n junction was reversed when the structure was subjected to vacuum annealing at 673 K.

Element-specific investigations of ultrafast dynamics in photoexcited Cu2ZnSnS4 nanoparticles in solution

Ultrafast, light-induced dynamics in copper–zinc–tin–sulfide (CZTS) photovoltaic nanoparticles are investigated through a combination of optical and x-ray transient absorption spectroscopy. Laser-pump, x-ray-probe spectroscopy on a colloidal CZTS nanoparticle ink yields element-specificity, which reveals a rapid photo-induced shift of electron density away from Cu-sites, affecting the molecular orbital occupation and structure of CZTS. We observe the formation of a stable charge-separated and thermally excited structure, which persists for nanoseconds and involves an increased charge density at the Zn sites. Combined with density functional theory calculations, the results provide new insight into the structural and electronic dynamics of CZTS absorbers for solar cells.

Modeling and performance optimization of two‐terminal Cu 2 ZnSnS 4 –silicon tandem solar cells

A dual-junction Cu2ZnSnS4–Silicon (CZTS–Si)-based tandem configuration is modeled and analyzed for its viability as a solar cell. The top and bottom modules in the tandem structure are validated by comparison with experiment. Initially, the designed tandem structure yields very low efficiency of 3.18%, and the various loss mechanisms are identified and investigated. The current mismatch between top and bottom cells and parasitic absorption (photon losses) are suggested to be the major causes limiting the short circuit current and hence the efficiency of the device. We optimize the material parameters within experimentally achievable limits in order to obtain current matching, and the optimized thicknesses of copper zinc tin sulfide (CZTS) and silicon (Si) absorbers are found to be 150 nm and 250 μm, respectively. The simulation results revealed that the photon losses are reduced, and overall absorption in the longer wavelength region has enhanced with the replacement of cadmium sulfide (CdS) by zinc sulfide (ZnS) buffer and careful optimization of the front layers of the device. The maximum predicted efficiency of tandem structure is >20% by minimizing the recombination centers within the experimentally obtainable ranges and improving the carrier separation process.

Polyethersulfone membranes modified with CZTS nanoparticles for protein and dye separation: Improvement of antifouling and self-cleaning performance

In this study, a novel polyethersulphone (PES) nanocomposite membrane incorporated with copper zinc tin sulfide (Cu2ZnSnS4) nanoparticles (CZTS NPs) was prepared through the phase inversion method. First, the samples containing different copper and zinc ratios in CZTS stoichiometry were prepared and characterized. The effect of copper and zinc ratio changes were examined on the photocatalytic properties of both NPs and nanocomposite membranes. The photocatalytic effect was tested and BR18 dye was degraded at 88.0% efficiency when exposed to visible light for 180 min in the presence of CZTS1.0 NPs catalyst. The results also exhibited that CZTS NPs blended membrane showed good self-cleaning performance. Second, we investigated the antioxidant, DNA cleavage, and biofilm inhibition activities of CZTS NPs. The antimicrobial activities of CZTS NPs were tested against seven microbial strains. The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and chelating activities were found as 81.80 ± 1.75% and 72.19 ± 4.63%, respectively. CZTS NPs exhibited double-strand DNA cleavage activity at 500 mg/L. They showed significant biofilm inhibition as 92.15 ± 5.67% against Staphylococcus aureus. CZTS NPs displayed moderate antimicrobial effects against tested microorganisms. Third, CZTS NPs were blended in polyethersulphone (PES) membrane and the morphology as well as performance of the fabricated nanocomposite membranes were systematically investigated by SEM-EDX, porosity, water contact angle, antifouling, and rejection measurements. The water flux of resulting nanocomposite membranes was markedly enhanced due to the introducing of CZTS NPs. Meanwhile, the nanocomposite membranes demonstrated remarkable antifouling properties (flux recovery ratio ∼94%) in contrast with the bare PES (flux recovery ratio ∼51%) when BSA was filtrated. The high retention of BSA (100%) as well as high permeation flux (73.8 ± 9.8 L/m2/h) of the CZTS2.00 wt% membrane demonstrated that the constructed nanocomposite membrane possessed the characteristics of a promising membrane for purification of proteins.

A Critical Review of Cu2SnS3 (CTS) Thin Films Solar Cells

To increase energy demand, reliability, and increasing efficiency, thin-film solar cells get the main focus. Various types of solar cell like (Cu(In,Ga)Se2 (CIGS), Cadmium telluride (CdTe) and copper zinc tin sulfide (CZTS) based absorber compound now eliminated by CTS (Cu2SnS3) for different reason like toxicity, shortage and structural complexity. Focus on CTS is increasing because it is nontoxic and it is environmentally friendly. CTS-based solar cell's power conversation efficiency increases and 30% theoretical efficiency indicates it's developing sign. For analyzing the synthesis property, X-ray diffraction (XRD), Raman, Energy Dispersive X-ray (EDX), X-ray fluorescence (XRF) techniques are used. For the synthesis of thin-film solar cells like CTS, different physical methods are used among all sputtering methods. The electron beam evaporation vacuum evaporation method has exposed better efficiency and high product quality and reliability. Additionally, the composition, variation of thickness, structural defects, and elemental composition make the absorber layer's quality affect the performance. This paper has discussed the annealing treatment of CTS-based solar cell synthesis, and it's essential to improve the thin film properties of thin films. This paper describes the reason for efficiency reduction also the scope for future research.

SiOxNy back-contact barriers for CZTSe thin-film solar cells.

The formation of molybdenum diselenide (MoSe2) is widely observed at the back-contact interface for copper zinc tin selenide (CZTSe) thin-film solar cells. Depending on individual selenium (Se) supply and thermal conditions for forming CZTSe absorbers on molybdenum (Mo) substrates, the thickness of MoSe2 can vary from a few hundreds of nanometers up to ≈ 1 μm, which is comparable to the commonly adopted thickness of 1 ~ 1.5 μm for CZTSe absorbers. In this study, for controlling the thickness of interfacial MoSe2, thin diffusion barrier layers of silicon oxynitride (SiOxNy) are deposited onto Mo layers prior to the growth of CZTSe absorbers in the fabrication process. As a result, a reduction in the thicknesses of MoSe2 layers is achieved. In terms of energy conversion efficiency (η), CZTSe solar cells grown on Mo/SiOxNy back contacts suffer a deterioration as the SiOxNy layers get thicker. CZTSe solar cells grown on Mo/SiOxNy/Mo back contacts preserve their efficiencies at ≈ 11% with thin 10 nm SiOxNy layers.

Doping-Induced Charge Localization Suppresses Electron-Hole Recombination in Copper Zinc Tin Sulfide: Quantum Dynamics Combined with Deep Neural Networks Analysis.

Nonradiative electron-hole recombination constitutes a major route for charge and energy losses in copper zinc tin sulfide (CZTS) solar cells. Using a combination of nonadiabatic (NA) molecular dynamics and deep neural networks (DNN), we demonstrated that electron-hole recombination is notably retarded by doping with Ag and Ag+Cd. The replacement of lighter Cu and/or Zn with heavier Ag and/or Cd reduces the NA coupling by separating electron and hole wave functions. Such replacement suppresses atomic motions and makes the phonon modes move to low-frequency region, which reduces NA coupling further but inhibits decoherence. The small magnitudes of NA coupling beat the long coherence time, delaying the electron-hole recombination from the Ag+Cd-codoping to the Ag doping system compared with pristine CZTS. The NA couplings predicted by the DNN algorithm lead to the time scales in agreement with the direct simulations. The study provides a robust strategy to design high-performance CZTS solar cells.