Papers by Keyword: CZTS

Abstract: Doping CZTS (copper-zinc-tin-sulfide) by replacing zinc with cadmium atoms is a crucial process for improving its electrical and optical properties. The primary goal is to modify the bandgap and increase the electrical conductivity of the material to enhance its efficiency in solar cell applications. This substitution induces a phase transition in the crystal structure from kesterite (favorable for zinc) to stannite (stable for cadmium). Experimental results showed that the pure sample (x = 0) was unstable, with a large dispersion in the conductivity measurements. Adding cadmium at a low ratio (x = 0.01225) improved the stability of the measurements while the conductivity decreased to ~10 S/m due to distortion stress in the crystal lattice. Increasing the ratio to x = 0.0269 resulted in a dramatic jump in the conductivity (~56 S/m) which is an indication of the onset of the phase transition. A computer code based on the K-Means algorithm was used to analyze the dispersion of measurements and isolated the most statistically reliable group.

Abstract: Industrial dyes contained a wide range of organic compounds that could affect the environment and high dimensional challenges to humans. In recent years, the environmentally safe and inexpensive quaternary copper-based chalcogenide Cu₂ZnSnS₄ (CZTS) has emerged as a material for photovoltaics and photocatalysis. CZTS nanoparticles were prepared in this investigation using the hydrothermal route at 210 °C for 24 h without the addition of a surfactant or capping agents. Rhodamine B (RhB), a carcinogenic dye, was degraded using the synthesized material through a photocatalytic process. The structural, morphological, optical, and photocatalytic characteristics of CZTS nanoparticles were examined using X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), and UV-vis spectroscopy. The average particle size of CZTS is found to be 31 nm with crystalline nature have been characterized by XRD. The results demonstrate that the synthesized sample has mixed morphological structures such as clew-like and flower-like structures and a bandgap of 1.50 eV. CZTS nanoparticles were used as photocatalysts under direct sunlight for Rhodamine B degradation, with the fastest degradation efficiency of 72% at 50 minutes. The results show that surfactant-free hydrothermally synthesized CZTS nanoparticles are a very promising material for the degradation of RhB dye due to the rapid degradation rate and high degradation efficiency.

Abstract: Among the second-generation solar cells, thin-film solar cells based on CIGS, CZTS and CdTe are well known due to their higher efficiencies, low cost and simple fabrication techniques. In this proposed work, we are committed to developing CZTS and ZnS thin films for second-generation thin-film photovoltaics. CZTS and ZnS have energy band gap of 1.4-1.5 eV and 3.6 eV, while their light absorption coefficients are 10⁴ cm^-1 and 3.3×10⁴ cm^-1 respectively. In thin film solar cells, absorber layer consists of photovoltaic material that should have optimal bandgap close to 1.34 eV. Moreover, a wide band gap window layer acts as p-n junction with absorber layer. In this work, we are reporting the synthesis of CZTS and ZnS thin films via wet chemistry route using spin coating method. Deposition of thin films on SLG substrate were carried out at specific process parameters such as spinning speed, concentration of precursors and annealing temperature to get the optimized thin film suitable for photovoltaic applications. Surface morphology and elemental compositional analysis investigated through SEM and EDX spectroscopy respectively. Electrical and optical properties were examined via Hall effect measurements and UV-VIS NIR spectrophotometry respectively. In addition micro-chemical and functional group analysis were conducted by FRIT spectroscopy. Keywords: Thin film PV, wet-chemistry, CZTS, ZnS

Abstract: Semiconductor alloy films of Cu₂ZnSn_1-xGe_xS₄ (CZTGS) were prepared by deposition and sintering of mixed nanoparticle suspensions composed of Cu₂ZnSnS₄ (CZTS) and Cu₂ZnGeS₄ (CZGS) nanoparticles with 1-dodecanethiol surfactant. Colloidal CZTS and CZGS nanoparticles were synthesized via the liquid-phase route and used without post-processing treatment. The CZTGS films are crystallized in the form of kesterite structures and form an alloy of CZTS and CZGS without an apparent phase separation. The Sn/Ge ratios in the alloy films were finely controlled by tuning a mixing ratio between CZTS and CZGS nanoparticles. The bandgap energy of the CZTGS film systematically increased from 1.6 to 2.1 eV as the Ge-substitution for Sn in the films proceeded, which indicates the potential of the fabrication method in the manufacture of bandgap-tuned multinary semiconductor thin films.

Abstract: This paper reports the preliminary study on the synthesis of Ni doped CZTS (Cu₂ZnSnS₄:Ni) particle 5 at.% of Cu by solution method and dispersion of the obtained particles by beads mill method at various dispersing agents (SDS, CTAB, and Tween80). The phase transformation of the obtained particles was analyzed from the XRD spectra and XRF elemental analysis. The phase transformation and amount of Ni-doped to particles was predicted employing commercially available analytical software tool Match! Version 2.x. Moreover, the dispersion characteristics were investigated includes size, size distribution, and zeta potential of bare particles in comparison to various dispersing agents. This characteristic related to the future application of CZTS as an absorber in a thin-film based PV. The XRD analysis showed that the obtained particle contained crystal structure of copper sulfate pentahydrate (75.9 %), Ni(HN₂S₂)₂ (12.5 %), and Cu₂ZnSnS₄ (11.6%). The XRF elemental analysis showed that amount of Ni-doped was 6.8 at.%; it was higher than the initial design amount of Ni doping. The dispersion of suspended particles was the majority (90%) with an average size of 3.06 µm and only 10 % with size 255 nm. Beads-milling of particles without dispersing agents did not disintegrate agglomerated particles. It is highlighted dispersion only using magnetic stirred with SDS dispersing agent provides the best suspension with a majority (60%) in 166 nm and only 30 % with average size 3.06 µm with relatively high zeta potential (-17 mV). It was concluded that the presence of a multi-phase crystal needs to be resolved either by proper calcination at a higher temperature than 400°C or further heating at a higher temperature during film preparation. High-energy centrifugation of zirconia beads mill caused desorption of adsorbed steric stabilization of dispersing agent under investigation. Further investigation on the coating process to facilitated laboratory fabrication of thin-film absorber with SDS as a dispersing agent is necessary to carry out concerning the properties of the thin-film.

Abstract: Copper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps – which are well-known to be beneficial for CIGS solar cell processing – are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al₂O₃ surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.

Abstract: The total energy, the electronic properties, phase transitions, and elastic properties of Cu₂ZnSnS₄ (CZTS) in the three structures are investigated by first-principles calculations based on density functional theory. Results show that the total energies of stannite (ST) and primitive-mixed CuAu (PMCA) structures are higher than that of kesterite-type (KS), and the KS is the ground state structure. Relationships between enthalpy and pressure of the KS, ST and PMCA structure of CZTS are also investigated at 0 K, since the pressure can have profound impacts on the electronic structure, possible phase transitions and structure stability. And results also show that KS structure is always the most stable; ST is the second; and the PMCA structure is the most unstable; phase transitions of three structures could not occur in high pressure. The high ratios of shear modulus to bulk modulus (G/B) indicate that CZTS compounds in three types have ductile behaviors. The Poisson ratios for the three structures are from 0.27 to 0.31, which again proves that all structures of CZTS have better plasticity. The results can increase more hints about further research directions, and these effects can play an important role in future experimental preparation technology and theoretical work of CZTS materials.

Abstract: Chalcopyrite ternary and kesterite quaternary thin films, such as Cu (In,Ga)(S,Se)₂ and Cu₂ZnSn (S,Se)₄ generically referred to as CIGSSe and CZTSSe, respectively, have become the subject of considerable interest and study for semiconductor devices in recent years [1,2]. These materials are of particular interest for use as an absorber layer in photovoltaic devices. In thin film solar cells, the p-type CIGSSe or CZTSSe layer is combined with an n-type semiconductor thin film such as CdS buffer layer to form the p-n heterojunction of the device. The synthesis process of the CIGSSe or CZTSSe absorber layer requires temperatures ranging between 400 and 600 °C to form the photoactive chalcopyrite or kesterite phases [3,4]. During the synthesis process, the formation of trace amounts of binary/ternary compositions (i.e., undesirable secondary or impurity phases consisting of selenides, oxides, carbonates, etc.) may occur. These trace amounts of impurity phases may form at the nascent absorber surfaces, which could negatively affects the photovoltaic conversion efficiencies of solar cells [5-7]. Therefore, prior to the deposition of the CdS buffer layer, there is a need to clean the CIGSSe or CZTSSe surfaces to remove any possible traces of such impurities.

Abstract: CZTS thin films were fabricated through sulfurization of sputtered alloy precursors. The properties of CZTS films obtained at sulfurization time of less than 2 hours and at H₂S concentrations of higher than 15% were investigated. Sulfurization time of 30 min, 60 min and 90 min and H₂S concentrations of 20%, 40% and 60% have been chosen for the sulfurization process. It has been found that Cu poor and slightly Zn rich CZTS films can be obtained at all of those sulfurization time and H₂S concentrations. Changing the sulfurization time or H₂S concentrations wont change the compositions of sulfurized films. Minor SnS coexist with the dominate CZTS although the films are Zn rich and the distributions of Sn and S along the depth of the films are uniform. The films sulfurized at H₂S concentration of 20% have the biggest grain size of exceeding 2 μm and obvious columnar CZTS grains can be observed across the whole cross-section.

Abstract: CZTS thin film, a potential candidate for application as absorber layer in thin film solar cells, has drawn much attention in these years due to its excellent photoelectric performance and nontoxic components. It provides a brief description of the development of CZTS thin film for solar cells, and surveys several methods of depositing CZTS films, then introduces the crystal structure of CZTS which is a problem for composition ratio affecting the properties of CZTS thin films. Here we also outline the development and the structure of solar cells based on CZTS thin films.