One-Step Electrodeposition of CuZnSn Metal Alloy Precursor Film Followed by the Synthesis of Cu2ZnSnS4 and Cu2ZnSnSe4 Light Absorber Films and Heterojunction Devices (original) (raw)
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Progress in Photovoltaics: Research and Applications, 2015
The impacts of preheating of an electrodeposited Cu/Sn/Zn (CTZ) stack precursor on structural changes of the CTZ precursor and the impact on structural and electric properties of the finally obtained Cu 2 ZnSnS 4 (CZTS) films are discussed in detail. We found that preheating for relatively long durations improved the qualities of CZTS films: these films were composed of large grains and had compact and flat surface morphologies. The best solar cell with efficiency of 8.1% was obtained on the basis of a CZTS film derived from the CTZ precursor preheated for 200 min. The external quantum efficiency response of the cell indicated efficient utilization of photons with relatively long wavelength regions because of its good structural and electronic properties. On the other hand, a short circuit current density-temperature property of one of the best cells in this study suggested that the CZTS film had deep acceptor levels and/or an appreciable energy barrier to the Mo back contact. Moreover, an open circuit voltage-temperature property of the corresponding device showed activation energy of 1.18 eV, indicating preferential occurrence of CdS-CZTS interface recombination.
Journal of Applied Physics, 2016
Cu-based chalcogenides are promising materials for thin-film solar cells with more than 20% measured cell efficiency. Using first-principles calculations based on density functional theory, the optoelectronic properties of a group of Cu-based chalcogenides Cu2-II-IV-VI4 is studied. They are then screened with the aim of identifying potential absorber materials for photovoltaic applications. The spectroscopic limited maximum efficiency (SLME) introduced by Yu and Zunger is used as a metric for the screening. After constructing the current-voltage curve, the maximum spectroscopydependent power conversion efficiency is calculated from the maximum power output. The role of the nature of the band gap, direct or indirect, and also of the absorptivity of the studied materials on the maximum theoretical power conversion efficiency is studied. Our results show that Cu2II-GeSe4 with II=Cd and Hg, and Cu2-II-SnS4 with II=Cd and Zn have a higher theoretical efficiency compared to the materials currently used as absorber layer.
The surface analyses by X-ray photoelectron spectroscopy (XPS) of Cu 2 ZnSnS 4 polycrystalline of thin film growth using physical vapor deposition (PVD) starting from metallic precursor in atmosphere of S 2 , were studied. Binding energies at 161.5 eV, 486.1 eV, 932.4 eV and 1021.6 eV were found for S 2p 3/2 , Sn 3d 5/2 , Cu 2p 3/2 and Zn 2p 3/2 , respectively. SEM and EDAX analyses show the morphology and elemental composition of Kesterite CZTS with Sn looses giving a Cu poor and Zn rich structure. Keywords: X-ray photoelectron spectroscopy, Timing analysis, Cu 2 ZnSnS 4 , EDAX RESUMEN El análisis de superficie por (XPS) Espectroscopia Fotoelectrónica de Rayos-x de películas delgadas policristalinas del compuesto Cu 2 ZnSnS 4 fueron sintetizadas empleando la técnica (PVD) Physical Vapor Deposition, partiendo de los precursores metálicos en atmosfera de Azufre en un proceso de co-evaporación de tres etapas. Las energías de enlace a 161.5 eV, 486.1 eV, 932.4 eV y 1021.6 eV fueron enc...
Latvian Journal of Physics and Technical Sciences, 2021
The study focuses on the optical properties of the CZTS multicomponent semiconductor absorber with 3 % “production” impurities of Cd, Na, O within the framework of the density functional theory using the generalized gradient approximation and the SCAPS program, as well as investigates their influence on the performance and efficiency of CZTS-solar cells. The results showed that the introduction of Cd, Na, O impurities would lead to a decrease in the intensity of the absorption bands at 2.06 eV and 2.55 eV. The density of states CZTS: (Cd, Na, O) was determined from first principles, and it was revealed that impurities of Cd and O atoms would lead to a decrease in the band gap (to 0.9 eV and 0.79 eV), and an increase in Na impurity absorption (1.2 eV). It was also found that a decrease in the band gap led to a decrease in the open circuit voltage, and it was also shown that “industrial” impurities led to a decrease in the efficiency of energy conversion of solar cells to 2.34 %.
Photoelectrochemical Characterization of Nanocrystalline Thin-Film Cu 2 ZnSnS 4 Photocathodes
ACS Applied Materials & Interfaces, 2011
Supporting Information Experimental Details CZTS Nanocrystal Synthesis. Copper(II) acetylacetonate (Cu(acac) 2 , Aldrich, 99.99%), tin(IV) acetate (Sn(OAc) 4 , Aldrich), zinc acetate (Zn(OAc) 2 , Fisher), sulfur powder (S, Aldrich), trioctylphosphine oxide (TOPO, Aldrich, 99%), and oleylamine (OLA, Aldrich, 70%) were purchased and used as received. All reaction conditions were kept inert to prevent the formation of an oxide. For Reaction A (stoichiometric), 0.50 mmol Cu(acac) 2 , 0.25 mmol Zn(OAc) 2 , 0.25 mmol Sn(OAc) 4 , and 4 mL OLA were prepared in a 25 mL 3-neck round-bottom reaction flask and heated under vacuum to 150 °C for 15 minutes. The temperature was lowered to 125 °C and the mixture remained at this temperature under vacuum until injection. In a 20 mL scintillation vial, 1.0 mmol S powder and 1 mL OLA was sonicated until the S had dissolved. In a 50 mL 3-neck round-bottom reaction flask, 10 mmol TOPO was heated to 300 °C on an Ar Schlenk line. When the TOPO reaction temperature reached 300 °C, simultaneously the S and metal precursors were rapidly injected via two gas-tight Luer-Lock syringes. The reaction was quenched at 45 minutes by extracting the product solution from the reaction flask and adding minimal amounts of hexanes to prevent it from solidifying when cooled to room temperature. Methanol was added to the product, which was subsequently centrifuged to precipitate the particles from solution. The CZTS nanocrystals were washed 3x with hexanes and methanol, and then resuspended in hexanes. Reaction B was similar with adjustments to the precursor ratios, shown in Table S1. Materials Characterization. Low-magnification TEM images were obtained on a JEOL JEM 2000 at a working voltage of 160 kV. TEM samples were prepared by dip-casting CZTS nanocrystals dispersed in hexanes onto carbon-coated copper TEM grids (200 mesh, Structure Probe, Inc.). SEM imaging was performed using a JEOL JSM 6500F FE-SEM and a JEOL JSM 7000F FE-SEM that was equipped with EDAX Genesis energy dispersive spectroscopy detector. Images were acquired under a working voltage of 15 kV and working distance of 10 mm. XRD was performed on a Scintag X-2 Advanced Diffraction System equipped with Cu Kα radiation (λ=1.54 Å) using a dried powder sample of the CZTS nanocrystals. UV-vis spectra were collected for CZTS thin films using a dual beam Cary 500 UV-VIS-NIR spectrophotometer, with an FTO-coated glass substrate as the reference/blank. The thin films were prepared by dip-casting onto FTO-coated glass substrates. Absorption coefficients, α, were calculated by Abs/l, where l is the film thickness determined by SEM. Photoelectrochemical
Journal of Applied Physics, 2006
The application of Zn compounds as buffer layers was recently extended to wide-gap CuInS 2 ͑CIS͒ based thin-film solar cells. Using an alternative chemical deposition route for the buffer preparation aiming at the deposition of a single-layer, nominal ZnS buffer without the need for any toxic reactants such as hydrazine has helped us to achieve a similar efficiency as respective CdS-buffered reference devices. After identifying the deposited Zn compound, as ZnS / Zn͑S,O͒ bilayer buffer in former investigations ͓M. Bär et al., J. Appl. Phys. 99, 123503 ͑2006͔͒, this time the focus lies on potential diffusion/intermixing processes at the buffer/absorber interface possibly, clarifying the effect of the heat treatment, which drastically enhances the device performance of respective final solar cells. The interface formation was investigated by x-ray photoelectron and x-ray excited Auger electron spectroscopy. In addition, photoelectron spectroscopy ͑PES͒ measurements were also conducted using tunable monochromatized synchrotron radiation in order to gain depth-resolved information. The buffer side of the buffer/absorber heterointerface was investigated by means of the characterization of Zn͑S,O͒ / ZnS / CIS structures where the ZnS / Zn͑S,O͒ bilayer buffer was deposited successively by different deposition times. In order to make the ͑in terms of PES information depth͒ deeply buried absorber side of the buffer/absorber heterointerface accessible for characterization, in these cases the buffer layer was etched away by dilute HCl aq . We found indications that while ͑out-leached͒ Cu from the absorber layer forms together with the educts in the chemical bath a ͓Zn ͑1−Z͒ ,Cu 2Z ͔S-like interlayer between buffer and absorber, Zn is incorporated in the uppermost region of the absorber. Both effects are strongly enhanced by postannealing the Zn͑S,O͒ / ZnS / CIS samples. However, it was determined that the major fraction of the Cu and Zn can be found quite close to the heterointerface in the buffer and absorber layer, respectively. Due to this limited ͑in the range of one monolayer͒ spatial extent, these "diffusion" mechanisms were rather interpreted as a chemical bath deposition induced and heat-treatment promoted Cu-Zn ion exchange at the buffer/absorber interface. Possible impacts of this intermixing on the performance of the final solar cell devices will also be discussed.