Zn Layer Research Articles

IZO or IOH Window Layers Combined with Zn(O,S) and CdS Buffers for Cu(In,Ga)Se2 Solar Cells

CdS and Zn(O,S) grown by chemical bath deposition are well‐established buffer materials for Cu(In,Ga)Se2 (CIGS) thin‐film solar cells and modules. Typically these buffers were combined with a ZnO:Al (AZO) or ZnO:B window layer and i‐ZnO or (Zn,Mg)O as high‐resistive interlayer. Nowadays, alternative transparent conductive oxide (TCO) materials with higher mobility as compared to AZO like indium zinc oxide (IZO) and hydrogen‐doped indium oxide (IOH) are under investigation. In the present contribution, we report on the performance of CIGS cells with solution‐grown Zn(O,S) or CdS buffer layers in combination with different stacking sequences including i‐ZnO, (Zn,Mg)O, IZO, and IOH. Devices with the commonly used AZO window layer are used as references. Efficiencies above 16% without anti‐reflective coating (ARC) are achieved for cells with Zn(O,S)/(Zn,Mg)O combined with IZO, IOH, and AZO whereas poor results are obvious with all Zn(O,S)/i‐ZnO combinations. Nevertheless, CdS‐buffered reference cells with the different TCO materials exhibit efficiencies in the range of 17–18% without ARC mainly due to higher open‐circuit voltages.

Deuterium Markers in CdS and Zn(O,S) Buffer Layers Deposited by Solution Growth for Cu(In,Ga)Se2 Thin‐Film Solar Cells

This contribution describes an easy and cheap approach to introduce deuterium (D) as an isotopic marker into the commonly used buffer layer materials CdS and Zn(O,S) for Cu(In,Ga)Se2 (CIGS) thin‐film solar cells. D was successfully incorporated during the growth of Zn(O,S) and CdS buffer layers by chemical bath deposition (CBD) with D2O. CIGS solar cells prepared with D‐containing buffers grown by CBD exhibit power conversion efficiencies above 16%, that is, the D content has no detrimental effect on the performance or other solar cell parameters of the devices. With depth profiles obtained by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) we clearly detect the intentionally incorporated D within the solution‐grown Zn(O,S) buffer. Assuming that D is present as OD, we compare the amount of OD within the Zn(O,S) layer with the amount of OH on the surface of the subsequent sputtered (Zn,Mg)O layer. Possible applications and future experiments of the method inserting isotopic markers such as D in functional layers of chalcopyrite‐type thin‐film solar cells and beyond are discussed.

Total Recovery of Gold Contained in Computer Printed Circuit Boards. Leaching Kinetics of Cu, Zn and Ni

In this study a thorough characterization of certain printed circuit boards has been carried out; it was found that they are made up of a polymer layer, a metal layer of Cu, Zn and Ni, and a gold substrate. A kinetic study of the acid dynamic leaching of copper, zinc and nickel has been carried out, finding out that these elements’ dissolution allows the gold substrate to be physically separated; then, the gold particles are separated from the polymer by filtration. The reaction orders were calculated vs. H2SO4 concentration, and the activation energy was calculated as well; reaction orders of n = 0.265, n = 0.247 and n = 0.245 were found for Cu, Zn and Ni respectively, while Ea = 86.3, Ea = 95.3 and Ea = 11.2 kJ/mol were found for Cu, Zn and Ni respectively. When the attack time is over, a shiny, solid product has been obtained; it was characterized by SEM-EDS and AAS, confirming that it is metallic gold, with a purity of 100 and 99.9% according to the respective technique.

Restraining the Band Fluctuation of CBD‐Zn(O,S) Layer: Modifying the Hetero‐Junction Interface for High Performance Cu2ZnSnSe4 Solar Cells With Cd‐Free Buffer Layer

Zn(O,S) film is a promising low‐cost and environment‐friendly Cd‐free buffer layer for chalcopyrite and kesterite thin film solar cells. However, the devices with Zn(O,S) buffer layer usually suffer from poor interface performance, resulting in a much lower efficiency, especially for kesterite solar cells. Here, the band fluctuation caused by ZnO secondary phase in Zn(O,S) layer is identified as the main reason deteriorating the device performance. By a concentrated ammonium etching and subsequent soft annealing treatment, the detrimental ZnO and Zn(OH)2 secondary phases are eliminated from the Zn(O,S) layer and the hetero‐junction performance is improved significantly. Consequently, the power conversion efficiency of the Zn(O,S)/CZTSe solar cells was improved from 1.17% to a favorable value of 7.2%. Temperature dependent J–V properties reveal a defect level assisted charge carrier transport mechanism across the Zn(O,S)/CZTSe interface. These encouraging results imply that Zn(O,S) buffer layer is a promising substitution for toxic CdS in future manufacturing of high performance thin film solar cells.

Mechanical and microstructural investigation of Zn/Sn multilayered composites fabricated by accumulative roll bonding (ARB) process

In the present research, Zn/Sn composites were produced for the first time by accumulative roll bonding (ARB) process up to seven cycles. The microstructure evolution was evaluated by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and the mechanical properties of Zn/Sn multilayered composites were measured by Vickers microhardness and tensile tests at different cycles of ARB process. It was observed that by increasing the ARB cycles, due to the differences in the mechanical behavior of the layers, Zn layers were necked at first, fractured and dispersed between Sn layers. After seven ARB cycles, a laminated composite with wavy interfaces and homogeneously distributed lenticular fragments of Zn was achieved. The XRD results showed that no new phase has been formed during the ARB process. Fracture surfaces of the samples after tensile tests were observed by SEM. Fracture surfaces revealed that fracture mode for the Zn layers was brittle at all cycles and fracture mode for the Sn layers was ductile at initial cycles and then changed to shear ductile fracture by increasing the ARB cycles.

Investigation of precursor sequence and post-annealing effects on the properties of Cu2SnZnSe4 thin films deposited by the elemental thermal evaporation

Cu2ZnSnSe4 (CZTSe) thin films were deposited onto soda lime glass substrates by thermal evaporation using the pure elemental sources. The influence of the sequential deposition order of Zn and Sn precursor layers for different evaporation cycles were investigated. In situ annealing at 400 °C under Se evaporation was applied to promote conversion of precursor layers to quaternary compound structure and additionally, subsequent post-annealing processes under nitrogen atmosphere at 450 °C was carried out to improve the crystalline behavior. The analyses concluded that the substrate temperature kept at 400 °C during selenization was not adequate to form homogenous CZTSe structure and as a result of post-annealing treatment, the polycrystalline quaternary CZTSe film structure was obtained. Structural analysis showed that in comparison with the initial Sn precursor layer, the growth process starting with Zn was found to be the preferable method to form better crystalline CZTSe structure. Furthermore, the stacking layer order and annealing processes showed the important effect on the stoichiometry and surface morphology of the films. The optical band gap energies were around 1.10 eV and also from Tauc plots, 1.40 eV was observed due to the admixture of secondary phases. The room temperature resistivity values and hole carrier densities were obtained around 10−2 Ω cm and 1019 cm−3, respectively. The mobility values of the samples were found in between 0.51 and 0.75 cm2 V−1 s−1.

One-stage pulsed laser deposition of conductive zinc oxysulfide layers

Zinc oxysulfide – Zn(O,S) is one of the prospective materials for substitution of conventional CdS buffer layer in complete optoelectronic devices due to its optimal bandgap and low toxicity. In this work Zn(O,S) thin films have been prepared by one-step pulsed laser deposition technique. The films with a thickness of 650nm were deposited onto the FTO/glass substrates at different substrate temperatures from room temperature to 400°C. Zn(O,S) layers were characterized by means of scanning electron microscopy, energy dispersive spectroscopy, Raman, X-ray diffraction, UV–vis spectroscopy and Van der Pauw technique. It was found, that obtained Zn(O,S) layers are mainly polycrystalline, highly uniform, transparent, electrically conductive and demonstrate good adhesion to the FTO/glass substrates. In addition, we show that elemental composition of PLD Zn(O,S) films depends on the substrate temperature. For the first time high quality single phase conductive Zn(O,S) layers were prepared by one stage PLD in high vacuum at relatively low temperature 200°C without any post treatment. The properties of prepared Zn(O,S) films suggest that these films can be applied as buffer layer in optoelectronic devices.

Development and characteristics of accumulative roll bonded Mg-Zn/Ce/Al hybrid composite

Accumulative roll bonding (ARB) process have been used develop Mg-2%Zn/Ce/Al hybrid composite and microstructure, mechanical and corrosion properties were investigated. The electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) revealed that the grains are significantly reduced and reaches up to 1 μm in Mg-2%Zn layer and 1.8 μm in Al layer having high angle misorientation of grain boundaries after subjected to 5-passes of the ARB process. The Al17Mg12, AlMg4Zn11 and Al11Ce3 intermetallic phases were observed through the XRD analysis. Mechanical properties of the hybrid composite improved with increase in the number of ARB passes which is attributed to work hardening, grain refinement and uniform distribution of Ce particles. Presence of Ce in the hybrid composite restricts the phenomenon of dynamic recrystallization and prevents the grain growth during ARB process. The corrosion rate of Mg-Zn/Ce/Al hybrid composite (0.72 mm/y) improved about 3.3 times as compared to that of Mg-2%Zn alloy (2.37 mm/y).

Enhancing mechanical stability and uniformity of 2-D continuous ZIF-8 membranes by Zn(II)-doped polydopamine modification

Zeolitic imidazolate framework-8 (ZIF-8) with regular pore size (~ 0.34nm) is widely attempted for gas separation membranes based on size sieving. However, the prospect is subjected to fabricating the continuous ZIF-8 membranes with high mechanical stability and uniformity. In response, an adhesive layer of Zn(II)-doped polydopamine (Zn-PDA) is pre-coated on the stainless steel nets in this work to improve ZIF-8 nucleation and growth. Zn-PDA layer shows high tolerance to ultrasonic agitation and heated methanol (system for ZIF-8 synthesis), little dissolution within 24h, which supplies a high stable surface for ZIF-8 growth. Furthermore, the Zn(II) doped in PDA layer is opportunely serving as the even-distributed ZIF-8 nucleation starting sites, verified with the EDX and FE-SEM images for the aggregated Zn(II) clusters and the nascent ZIF-8 crystals. Therefore, an indented and hinged boundary is constructed between ZIF-8 and substrate to enhance the mechanical stability. The FE-SEM images after ultrasonic agitation show that the continuous ZIF-8 membranes prepared on Zn-PDA layers can tolerate the deformation to a certain extent. Finally, the prepared ZIF-8 membranes behave excellently with αH2/CO2 = 9.9, αH2/CO = 17.2, αH2/CH4 = 26.0, and permeation rate JH2 = 3980 GPU. This work supplied a useful approach to enhance mechanical stability and uniformity of defect-free ZIF-8 membranes.

Application of EIS and SECM Studies for Investigation of Anticorrosion Properties of Epoxy Coatings Containing Zinc Oxide Nanoparticles on Mild Steel in 3.5% NaCl Solution

The effect of corrosion protection performance of epoxy coatings containing ZnO nanoparticle on mild steel in 3.5% NaCl solution was analyzed using scanning electrochemical microscopy and electrochemical impedance spectroscopy (EIS). Line profile and topographic image analysis were measured by applying −0.70 and +0.60 V as the tip potential for the cathodic and anodic reactions, respectively. The tip current at −0.70 V for the epoxy-coated sample with ZnO nanoparticles decreased rapidly, which is due to cathodic reduction in dissolved oxygen. The EIS measurements were taken in 3.5% NaCl after wet and dry cyclic corrosion test. The increase in the film resistance (R f) and charge transfer resistance (R ct) values was confirmed by the addition of ZnO nanoparticles in the epoxy coating. SEM/EDX analysis showed that complex oxide layer of zinc was enriched in corrosion products at a scratched area of the coated steel after corrosion testing. FIB-TEM analysis confirmed the presence of the nanoscale complex oxide layer of Zn in the rust of the steel that had a beneficial effect on the corrosion resistance of coated steel by forming protective corrosion products in the wet/dry cyclic test.

Investigation on the contact interface of Au/Zn on CdZnTe (111) B surface

In recent years, the quality and yield of CdZnTe material has steadily increased and now one of the limiting factors in performance of device is due to the quality of the metal contacts. A better understanding of the interface in metal-semiconductor contact can improve the performance of the detector. In this paper, Zn has been introduced as the intermediate layer between Au and CdZnTe (111) B surface. The structure and the chemical properties of Au/Zn-CdZnTe contact interface have been investigated by focused ion beam (FIB) cross section imaging, high resolution transmission electron microscopy (HRTEM) imaging and x-ray photoelectron spectroscopy (XPS) depth profiling. The results indicated that the Zn transition layer would be prone to combine with the dangling bonds of Te atoms on CdZnTe (111) B surface and help to avoid the emergence of the heterogeneous Te oxide (TeO2/CdTeO3) interface layer between the Au film and CdZnTe, contributing to form the impedanceless contact. Moreover, the electronic response of the Au/Zn-CdZnTe interface by using the circular transmission line model (CTLM) demonstrated that the introduction of Zn layer substantially decreased the specific contact resistivity (ρc), presenting a better ohmic performance.

Development and properties evaluation of Mg–6% Zn/Al multilayered composites processed by accumulative roll bonding

Abstract

Microstructural Evolution of 11Al-3Mg-Zn Ternary Alloy-Coated Steels During Austenitization Heat Treatment

This study details the microstructural evolution of a commercial hot-dip 11Al-3Mg-Zn-coated steel during austenitization. After 5 minutes of austenitization at 1173 K (900 °C), the ternary alloy coating transformed to consist of a nearly pure Zn as the major layer, a Fe-Al alloy layer at the interface, and a thin oxide overlay. The Fe-Al alloy layer effectively acted as the inhibition layer to prevent Fe from diffusing and reacting with Zn, which in turn retained the molten Zn layer and the integrity of the surface oxide layer. Moreover, the potential difference between the 11Al-3Mg-Zn coating and the steel substrate remained similar after austenitization, signifying the resulting coating kept its sacrificial protection capability.

Dissimilar spot welding of aluminium alloy and hot dip galvanised steel by metal flow: application of friction anchor welding to aluminium alloy and Zn-coated steel

Lap joints of an upper Al alloy (1.0 mm-thick A5052) and lower hot dip galvanized steel (1.2 mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding’. As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.

Heat dissipative Pb-free bonding technology using Al-rich Zn/Al/Zn clad solder

Al-rich Zn/Al/Zn clad solder were developed as Pb-free solder for a die-attachment. The Zn/Al/Zn clad solder was produced by clad rolling of Zn and Al strips in order to prevent Al from oxidation and improve wettability. The Zn/Al/Zn clad solder was melted at 382°C after solid-state interdiffusion of the Zn and Al layers. Bonding was successfully achieved with bonding pressure of a few kilopascals. Thermal cycle life of Invar-to-Cu substrate joint using the Zn/Al/Zn clad solder was longer than that of Pb-Sn-Ag solder. No Kirkendall voids were observed in the vicinity of the bonded interface after ageing at 250 °C for 1000 h.

Tunable optical and structural properties of Zn(S,O) thin films as Cd-free buffer layer in solar cells

Zn(S,O) thin films were grown by three step process: (1) the deposition of Zn layer on glass substrates by vacuum thermal evaporation, (2) the oxidation of the as-deposited Zn layer in air atmosphere and (3) the sulfurization of the oxidized samples in N2 atmosphere. The samples were analyzed for their microstructural, morphological and optical properties. XRD analysis revealed that the films were polycrystalline with a highly c-axis orientation. EDX measurements suggested that the sulfur content of the films could be inflected by the sulfurization temperature. The optical constants of the films were calculated from the analysis of the transmittance and reflectance data. The band gap energy varied from 3.27 to 3.08eV depending on the sulfur content. The surface morphological studies revealed that the films had an average roughness between 13.1 and 16.9nm. Zn(S,O) thin films exhibited n-type electrical conductivity.

Temperature-dependent growth of ZnO structures by thermal oxidation of Zn coatings electrodeposited on steel substrates and their photocatalytic activities

Abstract In this work, zinc oxide (ZnO) nanostructures were successfully synthesized by thermal oxidation of zinc (Zn) coated steel substrates. Zn coatings were electrodeposited on the mild carbon steel sheet in the sulfate bath by DC current. The zinc coated samples were oxidized in air at distinct annealing temperatures between 400 °C and 800 °C. The phase structure and surface morphology of the ZnO films were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of these ZnO layers was examined by means of decomposition of methylene blue (MB) aqueous solutions under UV lamp irradiation for various duration. The findings illustrated that annealing temperatures had a big effect on the morphology and structure of the ZnO layers. The annealed layers showed significantly enhanced photoactivity activity than the pure Zn layer under UV-irradiation. The sample with ZnO nanostructures oxidized at 800 °C exhibited a better photocatalytic degradation of MB than the other samples. This paper can provide an important contribution to the development of efficient photocatalysts for the solution of the environmental pollution problems.

Effect of a Zn interlayer on dissimilar FSSW of Al and Cu

The present paper focuses on the role played by a Zn interlayer in the improvement of the mechanical behavior of Al-Cu Friction Stir Spot Welds. An unusual configuration of lap joint with Cu at the top surface as well as rather thick plates was considered. The effects of the tool plunge depth exceeding or not the top plate thickness and of various Zn layer thicknesses on the microstructure and mechanical properties of the joint were investigated. Zn at once hampers the formation of the deleterious Al4Cu9 compound while favoring the τ′ phase precipitation. Over the range considered in this study, the Zn layer thickness presents no obvious effect on the shear lap tensile properties. At last, various ways of welding improvement are proposed.

Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite

Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 μm in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength (~1.82 times) and elongation (~1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process.

Surface ‐Area Enhanced Dealuminated Layered Double Hydroxides for Adsorption of Organic Compounds

AbstractRemoval of isomorphously substituted Al from the layer of Zn−Al LDHs by treating with organic acids like para‐toluenesulfonic acid, phenoldisulfonic acid followed by Ammonium hexafluro silicate under microwave irradiation result in increased surface area, generating materials which are highly mesoporous. The dealuminated Zn−Al LDHs were characterized by BET surface area, XRDand 27Al– NMR. Adsorption data of as‐synthesized and dealuminated Zn−Al LDHs for various polar and nonpolar organic compounds at different time intervals were evaluated. Adsorption data were fitted with the models such as fractional power, pseudo‐first order and Elovich models. The Elovich model provided high degree of correlation. Modified Zn‐Al LDH adsorbent showed increased adsorption of organic compounds compared to as‐synthesized Zn−Al LDH because of high surface area. Reusability of used adsorbent showed almost same adsorption capacity as the fresh adsorbent.