Dr. Mohamed Yassine ZAKI
Scientific Researcher
Laboratory of Complex Heterostructures and Multifunctional Materials
yassine[DOT]zaki[AT]infim[DOT]roResume
Dr. Mohamed Yassine ZAKI, Assistant researcher (since 2021), born in 1989, graduated the Faculty of Sciences – Specialization Metallurgy: Surface and Industrial Water Treatment at University of Ibn Tofail (UIT) (2012), Kenitra, Morocco, has a MSc degree in Functional Materials at University of Cadi Ayyad (UCA) (2015), Marrakech, Morocco, and a PhD degree in Physics and Applications obtained at University of Ibn Tofail, Kenitra, Morocco (2020). Work experience: National Institute of Materials Physics (NIMP) (2021 – to date); Eugen Ionescu doctoral scholarship (2019) at NIMP, financed by Agence Universitaire de Francophonie (AUF); Electrochemistry Practical Works Assistant (2018) – Faculty of Sciences (UIT), Kenitra, Morocco. Main areas of interest/expertise: materials characterization (ellipsometry, XRD, conventional UV-Vis, SEM-EDS, infrared spectroscopy, mechanical testing); preparation of chalcogenide semiconductor thin films by physical and chemical deposition methods (magnetron sputtering, electrodeposition). Publications (last updated November 2022): 11 articles published in Web of Science® (WoS) journals with impact factor (e.g. Sci. Rep., Appl. Surf. Sci. ACS Omega. Opt. Mater.; J. Alloy. Compd.; Mater. Sci. Semicond. Process.) Hirsch index (WoS): 5; Citations (without self-citations): 60. Coordinated projects: Post-Doctoral National Project (PD 41/2022) - Improving the efficiency of CZTSSe-based solar cells by CdS replacement and layer engineering (Project leader). Professional profile web-links: Brainmap: https://www.brainmap.ro/mohamed-yassine-zaki; ORCID ID: https://orcid.org/0000-0002-8606-1140; WoS ResearcherID: https://www.webofscience.com/wos/author/record/GZG-1856-2022.
Projects
1. Efficiency enhancement of thin films solar cells via CdS replacement and CZTSSe layer engineering (EECSC-23)
Project Type: PD, Start Date: 2022-04-01 End Date: 2024-03-31
Publications
1. Synthesis of WS2 Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space
Authors:
Sava, F; Simandan, ID; Buruiana, AT; Bocirnea, AE; El Khouja, O; Tite, T; Zaki, MY; Mihai, C; Velea, A
Published: MAR 2024, SURFACES, 7, DOI: 10.3390/surfaces7010008
In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications.
2. Recent Progress and Challenges in Controlling Secondary Phases in Kesterite CZT(S/Se) Thin Films: A Critical Review
Authors:
Zaki, MY; Velea, A
Published: APR 2024, ENERGIES, 17, 1600, DOI: 10.3390/en17071600
Kesterite-based copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) thin films have attracted considerable attention as promising materials for sustainable and cost-effective thin-film solar cells. However, the successful integration of these materials into photovoltaic devices is hindered by the coexistence of secondary phases, which can significantly affect device performance and stability. This review article provides a comprehensive overview of recent progress and challenges in controlling secondary phases in kesterite CZTS and CZTSe thin films. Drawing from relevant studies, we discuss state-of-the-art strategies and techniques employed to mitigate the formation of secondary phases. These include a range of deposition methods, such as electrodeposition, sol-gel, spray pyrolysis, evaporation, pulsed laser deposition, and sputtering, each presenting distinct benefits in enhancing phase purity. This study highlights the importance of employing various characterization techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, for the precise identification of secondary phases in CZTS and CZTSe thin films. Furthermore, the review discusses innovative strategies and techniques aimed at mitigating the occurrence of secondary phases, including process optimization, compositional tuning, and post-deposition treatments. These approaches offer promising avenues for enhancing the purity and performance of kesterite-based thin-film solar cells. Challenges and open questions in this field are addressed, and potential future research directions are proposed. By comprehensively analyzing recent advancements, this review contributes to a deeper understanding of secondary phase-related issues in kesterite CZT(S/Se) thin films, paving the way for enhanced performance and commercial viability of thin-film solar cell technologies.
3. Synthesis of Wrinkled MoS2 Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space
Authors:
Mihai, C; Simandan, ID; Sava, F; Buruiana, AT; Bocirnea, AE; Tite, T; Zaki, MY; Velea, A
Published: MAY 2024, SUSTAINABILITY, 16, 3819, DOI: 10.3390/su16093819
Considering the increasing need for sustainable and economical energy storage solutions, the integration of layered materials such as MoS2 into these systems represents an important step toward enhancing energy sustainability and efficiency. Exploring environmentally responsible fabrication techniques, this study assesses wrinkled MoS2 thin films synthesized from distinct Mo and MoS2 targets, followed by sulfurization conducted in a graphite box. We utilized magnetron sputtering to deposit precursor Mo and MoS2 films on Si substrates, achieving thicknesses below 20 nm. This novel approach decreases sulfur by up to tenfold during sulfurization due to the confined space technique, contributing also to avoiding the formation of toxic gases such as SO2 or the necessity of using H2S, aligning with sustainable materials development. Thinner MoS2 layers were obtained post-sulfurization from the MoS2 precursors, as shown by X-ray reflectometry. Raman spectroscopy and grazing X-ray diffraction analyses confirmed the amorphous nature of the as-deposited films. Post-sulfurization, both types of films exhibited crystalline hexagonal MoS2 phases, with the sulfurized Mo showing a polycrystalline nature with a (100) orientation and sulfurized MoS2 displaying a (00L) preferred orientation. The X-ray photoelectron spectroscopy results supported a Mo:S ratio of 1:2 on the surface of the films obtained using the MoS2 precursor films, confirming the stoichiometry obtained by means of energy dispersive X-ray spectroscopy. Scanning electron microscopy and atomic force microscopy images revealed micrometer-sized clusters potentially formed during rapid cooling post-sulfurization, with an increased average roughness. These results open the way for the further exploration of wrinkled MoS2 thin films in advanced energy storage technologies.
4. Anticorrosion Protection of New Composite Coating for Cobalt-Based Alloy in Hydrochloric Acid Solution Obtained by Electrodeposition Methods
Authors:
Branzoi, F; Mihai, AM; Zaki, MY; Xu, JY
Published: JAN 2024, COATINGS, 14, 106, DOI: 10.3390/coatings14010106
In this work, electrochemical deposition techniques (galvanostatic and potentiostatic) were used to obtain coatings of a new composite polymer, 3-methylpyrrole-sodium dodecyl sulfate/poly 2-methythiophene (P3MPY-SDS/P2MT), on cobalt-based alloy samples for anti-corrosion safety. The use of sodium dodecyl sulfate as a dopant ion in electrosynthesis can have a relevant effect on the anticorrosive property of the composite polymer layer by blocking the entry of corrosive ions. The cobalt alloy specimen had an important impact on the electrochemical performance of the composite coating and this together with the presence of the polymeric layer was achieved by simultaneously constitution of a complex oxides film and polymeric layers. The polymeric coatings were analyzed using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and cyclic voltammetry (CV) methods. The corrosion protection of the P3MPY-SDS/P2MT-covered cobalt-based alloy was explored using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization procedures in a 1 M HCl solution. The corrosion speed of the P3MPY-SDS/P2MT-covered cobalt-based alloy was observed to be similar to 10 times less than an uncovered specimen, and the effectiveness of the composite layers of this coating is greater than 91%. This superior efficaciousness was obtained by the electropolymerization of P3MPY-SDS/P2MT at current densities of 1 mA/cm(2) and 0.5 mA/cm(2), applied potentials of 0.9 V and 1.0 V, and a molar ratio of 5:1. Corrosion test results indicate that the P3MPY-SDS/P2MT coatings provide a good result: protection against the corrosion of a cobalt-based alloy in aggressive solutions.
5. The Inhibition Action of Some Brij-Type Nonionic Surfactants on the Corrosion of OLC 45 in Various Aggressive Environments
Authors:
Branzoi, F; Baran, A; Mihai, MA; Zaki, MY
Published: MAR 2024, MATERIALS, 17, 1378, DOI: 10.3390/ma17061378
The corrosion protection property of three Brij-type surfactants, namely, Brij 35, Brij 56 and Brij 58P, was considered on OLC 45 carbon steel in a 0.5 M H2SO4 medium. The efficacy for these organic compounds was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods, scanning electron microscopy (SEM) procedures, and Fourier transform infrared (FT-IR) spectroscopy. We hypothesized that these surfactants hinder the corrosion for OLC 45 samples through a protecting mechanism owing to the adsorption of organic molecules that form an inhibitive film or through the formation of complex oxides. These surfactants exhibited an appreciable protective effect against OLC 45 corrosion, operating as mixed inhibitors, as could be demonstrated by their influence on the electrochemical characteristics of the metallic substrates. The adsorption of surfactants over the substrates zone conformed to the representation of the Langmuir isotherm. The effect of temperature on the electrochemical comportment of the OLC 45 specimens in H2SO4 without and with Brij at 800 ppm was examined in the temperature interval of 293 to 333 K. The negative estimate of thermodynamic attributed as Gibbs free energy of adsorption presented the spontaneity of the adsorption activity. The investigation with FT-IR and SEM established the adsorption of Brij and the constitution of the corrosive components on the OLC 45 surface. Electrochemical determinations of these surfactants indicated its anticorrosion inhibition performance and the highest inhibition of 96% was reached when the Brij 35 concentration was at 800 or 1000 ppm, while for Brij 56 and Brij 58P, the highest inhibition was obtained when their concentrations were 500, 800, or 1000 ppm.
6. First Sharp Diffraction Peak features of the intermediate phase glasses and amorphous thin films in the non-stoichiometric (GeS4)x(AsS3)1-x system
Authors:
Ciobanu, M; Galca, AC; Sava, F; Zaki, MY; Velea, A; Tsiulyanu, D
Published: MAY 31 2023, THIN SOLID FILMS, 773, 139828, DOI: 10.1016/j.tsf.2023.139828
Grazing incidence X-ray scattering (GIXRS) patterns of thin solid films based on non-stoichiometric chalcogenide glasses (ChG) from the pseudo - binary system (GeS4)x(AsS3)1-x were studied with a focus on the First Sharp Diffraction Peak (FSDP), assigned to the middle range order (MRO) of the glassy material. The films were grown using explosive thermal evaporation in vacuum (10-4 Pa) of pulverized ChG, prepared from previously synthesized bulk glasses, onto mono-crystalline silicon substrates. Scanning Electron Microscopy (SEM) and EnergyDispersive X-ray (EDX) spectroscopy were used to examine the morphology and elemental composition of the films, which were found to have similar composition to the bulk glasses. However, it was revealed that the molecular structure of the grown amorphous films differs from that of the initial ChG bulk material, as indicated by changes in the composition-dependent position and width of the FSDP. Additionally, the intensities of the FSDP in the films were higher compared to those of the bulk samples, suggesting that the molecular-like structure of ChGs is more pronounced in the form of thin films grown from the vapor phase.
7. From non-stoichiometric CTSe to single phase and stoichiometric CZTSe films by annealing under Sn plus Se atmosphere
Authors:
Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Bocirnea, AE; Stavarache, I; Velea, A; Galca, AC; Pintilie, L
Published: NOV 1 2023, CERAMICS INTERNATIONAL, 49, DOI: 10.1016/j.ceramint.2023.08.056
One of the new materials for next-generation thin film solar cells is Cu2ZnSnSe4 (CZTSe). However, achieving a single-phase CZTSe compound remains a challenge. This study describes the development of Cu2ZnSnSe4 thin films through the sequential deposition of stacked films of non-stoichiometric Cu2SnSe3 (CTSe) and ZnSe by magnetron sputtering. The structural, morphological, and electrical properties as well as the surface chemistry of the films were investigated and compared depending on the growth sequence of the thin films. By using Raman spectroscopy and grazing incidence X-ray diffraction, the tetragonal CZTSe structure was confirmed. Scanning electron microscopy and energy-dispersive spectroscopy measurements of the morphological and compositional properties indicated large grains and dense surfaces with an elemental composition close to the desired stoichiometry in SLG\SnSe2\Cu\ZnSe and SLG\SnSe2\Cu2Se\ZnSe stacks. To ascertain the surface chemistry and unique characteristics of the produced films, additional X-ray photoemission spectroscopy experiments were carried out. The optimal band gap values for the absorber layers were found using conventional spectroscopy, and they ranged from 0.88 to 1.47 eV. According to the electrical measurements, all the films were p-type and have high carrier concentrations between 1016 and 1020 cm-3. Our findings demonstrate that employing a sequential deposition approach and annealing in different atmospheres can yield CZTSe absorber layers with desirable properties, overcoming the challenge of non-stoichiometric CTSe precursors.
8. Understanding the Effects of Post-Deposition Sequential Annealing on the Physical and Chemical Properties of Cu2ZnSnSe4 Thin Films
Authors:
Catana, DS; Zaki, MY; Simandan, ID; Buruiana, AT; Sava, F; Velea, A
Published: DEC 2023, SURFACES, 6, DOI: 10.3390/surfaces6040031
Cu2ZnSnSe4 thin films have been synthesized by employing two magnetron-sputtering depositions, interlaced with two sequential post-deposition heat treatments in low vacuum, Sn+Se and Se-rich atmospheres at 550 degrees C. By employing successive structural analysis methods, namely Grazing Incidence X-Ray Diffraction (GIXRD) and Raman Spectroscopy, secondary phases such as ZnSe coexisting with the main kesterite phase have been identified. SEM peered into the surface morphology of the samples, detecting structural defects and grain profiles, while EDS experiments showed off-stoichiometric elemental composition. The optical bandgaps in our samples were calculated by a widely used extrapolation method from recorded transmission spectra, holding values from 1.42 to 2.01 eV. Understanding the processes behind the appearance of secondary phases and occurring structural defects accompanied by finding ways to mitigate their impact on the solar cells' properties is the prime goal of the research beforehand.
9. Cu2SnSe3 phase formation from different metallic and binary chalcogenides stacks using magnetron sputtering
Authors:
Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Mihai, C; Velea, A; Galca, AC
Published: JAN 2023, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 153, 107195, DOI: 10.1016/j.mssp.2022.107195
Cu2SnSe3 (CTSe) is a polyvalent material that can be used as an absorber layer for thin film solar cells or as a starting layer for the synthesis of CZTSe or CZTSSe compounds. Obtaining CTSe single phase films with opti-mized properties for thin film solar cells is a difficult task. A systematic study using both metallic and binary chalcogenides precursors for the formation of the CTSe phase was not performed. The films consisting of four different stacks (Sn\Cu, SnSe2\Cu, Sn\Cu2Se, and SnSe2\Cu2Se) were prepared by magnetron sputtering on soda lime glass (SLG) and molybdenum (Mo) coated SLG substrates, followed by annealing at 550 degrees C under Sn + Se atmosphere. X-ray diffraction and Raman spectroscopy results indicated the formation of a single CTSe phase in most of the stacks deposited on both substrates. Scanning electron microscopy images showed compact surfaces with large grains in the films deposited on Mo substrate, while the films on SLG have more voids on their sur-faces. The elemental analysis measured by energy dispersive spectroscopy revealed stoichiometric films on Mo, and copper and tin rich compositions on SLG substrates. The band gap values inferred by conventional spec-troscopy are between 0.81 and 1.95 eV. It was found that the SnSe2\Cu and Sn\Cu2Se stacks are preferred for the formation of a single CTSe phase, with dense surface morphology, a stoichiometric composition, and an optimal absorber layer band gap. This study opens the way to comprehend the formation reactions during the seleni-zation of metallic and binary chalcogenides precursors towards the optimization of kesterite absorber for photovoltaic device fabrication.
10. ZnS stacking order influence on the formation of Zn-poor and Zn-rich Cu2ZnSnS4 phase
Authors:
Zaki, MY; El Khouja, O; Nouneh, K; Touhami, ME; Matei, E; Azmi, S; Rusu, MI; Grigorescu, CEA; Briche, S; Boutamart, M; Badica, P; Burdusel, M; Secu, M; Pintilie, L; Galca, AC
Published: MAY 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 33, DOI: 10.1007/s10854-022-08160-6
This paper reports the synthesis and characterization of Cu2ZnSnS4 (CZTS) absorber films, prepared by a two-step electrodeposition of a ZnS (zinc sulfide) binary and a CZT (copper, zinc and tin) ternary precursors on Mo/Ti/Si substrates. The as-electrodeposited ZnS/CZT and CZT/ZnS stacks were thermally treated in a tubular furnace in sulfur environment at 550 degrees C. The role of the ZnS buffer layer is to provide a zinc and sulfur reservoir, needed to complete the formation of kesterite phase. X-ray diffraction and Raman analyses revealed the formation of the CZTS phase. The surface morphology and chemical composition of the films were studied using a scanning electron microscope. The bandgap values inferred from diffuse reflectance data, are discussed with respect to the stoichiometry which is considerably affected by the order of the stacks. Room-temperature photoluminescence of the CZT/ZnS sample showed a board PL band of 1.51 eV. It was found that the film with a ZnS layer on top is preferred for the formation of a Zn-rich single CZTS phase.
11. ZnS stacking order influence on the formation of Zn-poor and Zn-rich Cu2ZnSnS4 phase
Authors:
Zaki, MY; El Khouja, O; Nouneh, K; Touhami, ME; Matei, E; Azmi, S; Rusu, MI; Grigorescu, CEA; Briche, S; Boutamart, M; Badica, P; Burdusel, M; Secu, M; Pintilie, L; Galca, AC
Published: APR 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, DOI: 10.1007/s10854-022-08160-6
This paper reports the synthesis and characterization of Cu2ZnSnS4 (CZTS) absorber films, prepared by a two-step electrodeposition of a ZnS (zinc sulfide) binary and a CZT (copper, zinc and tin) ternary precursors on Mo/Ti/Si substrates. The as-electrodeposited ZnS/CZT and CZT/ZnS stacks were thermally treated in a tubular furnace in sulfur environment at 550 degrees C. The role of the ZnS buffer layer is to provide a zinc and sulfur reservoir, needed to complete the formation of kesterite phase. X-ray diffraction and Raman analyses revealed the formation of the CZTS phase. The surface morphology and chemical composition of the films were studied using a scanning electron microscope. The bandgap values inferred from diffuse reflectance data, are discussed with respect to the stoichiometry which is considerably affected by the order of the stacks. Room-temperature photoluminescence of the CZT/ZnS sample showed a board PL band of 1.51 eV. It was found that the film with a ZnS layer on top is preferred for the formation of a Zn-rich single CZTS phase.
12. A Two-Step Magnetron Sputtering Approach for the Synthesis of Cu2ZnSnS4 Films from Cu2SnS3\ZnS Stacks
Authors:
Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Stavarache, I; Bocirnea, AE; Mihai, C; Velea, A; Galca, AC
Published: JUN 2022, ACS OMEGA, DOI: 10.1021/acsomega.2c02475
Cu2ZnSnS4 (CZTS) is regarded as one of the emerging materials for next-generation thin film solar cells. However, its synthesis is complex, and obtaining a single-phase CZTS thin film is difficult. This work reports the elaboration of Cu2ZnSnS4 thin films by a sequential magnetron sputtering deposition of Cu2SnS3 (CTS) and ZnS as stacked films. Initially, the CTS films were prepared on a soda lime glass substrate by annealing Cu and SnS2 stacked layers. Second, ZnS was deposited by magnetron sputtering on the CTS films. The CTS\ZnS stacks were then annealed in Sn + S or S atmospheres. The tetragonal CZTS structure was obtained and confirmed by grazing incidence X-ray diffraction and Raman spectroscopy. The morphological and compositional characteristics, measured by scanning electron microscopy and energy-dispersive spectroscopy, revealed large grains and dense surfaces with the elemental composition close to the intended stoichiometry. Additional X-ray photoemission spectroscopy measurements were performed to determine the surface chemistry and particularities of the obtained films. The optical properties, determined using conventional spectroscopy, showed optimal absorber layer band gap values ranging between 1.38 and 1.50 eV. The electrical measurements showed that all the films are p-type with high carrier concentrations in the range of 10(15) to 10(20) cm(-3). This new synthesis route for CZTS opens the way to obtain high-quality films by an industry-compatible method.
13. Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3
Authors:
Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Mihai, C; Velea, A; Galca, AC
Published: MAY 13 2022, SCIENTIFIC REPORTS, 12, 7958, DOI: 10.1038/s41598-022-12045-3
Cu2SnS3 (CTS) is emerging as a promising absorber for the next generation thin film solar cells (TFSC) due to its excellent optical and electronic properties, earth-abundance and eco-friendly elemental composition. In addition, CTS can be used as precursor films for the Cu2ZnSnS4 (CZTS) synthesis. The optical properties of CTS are influenced by stoichiometry, crystalline structure, secondary phases and crystallite size. Routes for obtaining CTS films with optimized properties for TFSC are still being sought. Here, the CTS thin films synthesized by magnetron sputtering on soda lime glass (SLG) using Cu and SnS2 targets in two different stacks, were studied. The SLG\Cu\SnS2 and SLG\SnS2\Cu stacks were annealed in S and Sn + S atmospheres, at various temperatures. Both stacks show a polymorphic structure, and higher annealing temperatures favor the monoclinic CTS phase formation. Morphology is influenced by the stacking order since a SnS2 top layer generates several voids on the surface due to the evaporation of SnS, while a Cu top layer provides uniform and void-free surfaces. The films in the copper-capped stack annealed under Sn + S atmosphere have the best structural, morphological, compositional and optical properties, with tunable band gaps between 1.18 and 1.37 eV. Remarkably, secondary phases are present only in a very low percent (< 3.5%) in samples annealed at higher temperatures. This new synthesis strategy opens the way for obtaining CTS thin films for solar cell applications, that can be used also as intermediary stage for CZTS synthesis.
14. Enhanced photoelectrochemical activity of WO3-decorated native titania films by mild laser treatment
Authors:
Spataru, T; Mihai, MA; Preda, L; Marcu, M; Radu, MM; Becherescu, ND; Velea, A; Zaki, MY; Udrea, R; Satulu, V; Spataru, N
Published: SEP 15 2022, APPLIED SURFACE SCIENCE, 596, 153682, DOI: 10.1016/j.apsusc.2022.153682
The effectiveness of the electrochemical WO3-modification as a method for improving the photoactivity of native air-formed TiO2 layers was assessed. The way in which a mild laser treatment influences the photo-electrochemical performances of the thus obtained WO3/TiO2 systems was also investigated. At laser-treated electrodes (L-WO3/TiO2), the melting-solidification process induced by the treatment led to a smaller size of the deposited WO3 particles and to their better dispersion on the surface. The treatment also enhanced the surface oxygen deficiency and ensured better relative absorptivity of the oxygenated species on the surface. These features, together with the intrinsic narrower bandgap of the WO3/TiO2 composites, the higher donor density and the lower flat band potential of L-WO3/TiO2 enabled faster kinetic of the oxygen photoanodic evolution. Importantly, the same process exhibited a cathodic shift of its onset potential. The laser treatment also strongly enhanced the photoelectrocatalytic performances for UV-assisted methanol anodic oxidation.
15. Structural, morphological and optical properties of Cu-Fe-Sn-S thin films prepared by electrodeposition at fixed applied potential
Authors:
El Khouja, O; Galca, AC; Nouneh, K; Zaki, MY; Touhami, ME; Taibi, M; Matei, E; Negrila, CC; Enculescu, M; Pintilie, L
Published: MAR 1 2021, THIN SOLID FILMS, 721, DOI: 10.1016/j.tsf.2021.138547
Cu-Fe-Sn-S films were obtained on indium tin oxide / glass substrates by a low-cost electrodeposition using an aqueous solution of CuSO4, FeSO4, SnSO4, and Na2S2O3 at room temperature followed by high-temperature sulfurization (500 degrees C) in argon flow. A range of cathodic potentials have been used for electrodeposition, those being chosen after a preliminary cyclic voltammetry study. The coatings were characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray Photoelectron Spectroscopy and conventional spectroscopy (diffuse reflectance and specular transmission). The results are discussed with respect to the used applied potential.
16. Synthesis and Characterization of Cu2ZnSnS4 Thin Films Obtained by Combined Magnetron Sputtering and Pulsed Laser Deposition
Authors:
Zaki, MY; Sava, F; Buruiana, AT; Simandan, ID; Becherescu, N; Galca, AC; Mihai, C; Velea, A
Published: SEP 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11092403
Cu2ZnSnS4 (CZTS) is a complex quaternary material, and obtaining a single-phase CZTS with no secondary phases is known to be challenging and dependent on the production technique. This work involves the synthesis and characterization of CZTS absorber layers for solar cells. Thin films were deposited on Si and glass substrates by a combined magnetron sputtering (MS) and pulsed laser deposition (PLD) hybrid system, followed by annealing without and with sulfur powder at 500 degrees C under argon (Ar) flow. Three different Cu2S, SnS2, and ZnS targets were used each time, employing a different target for PLD and the two others for MS. The effect of the different target arrangements and the role of annealing and/or sulfurization treatment were investigated. The characterization of the absorber films was performed by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), Raman spectroscopy, scanning electron microscopy, and regular transmission spectroscopy. The film with ZnS deposited by PLD and SnS2 and Cu2S by MS was found to be the best for obtaining a single CZTS phase, with uniform surface morphology, a nearly stoichiometric composition, and an optimal band gap of 1.40 eV. These results show that a new method that combines the advantages of both MS and PLD techniques was successfully used to obtain single-phase Cu2ZnSnS4 films for solar cell applications.
17. Secondary phases and their influence on optical and electrical properties of electrodeposited Cu2FeSnS4 films
Authors:
El Khouja, O; Galca, AC; Zaki, MY; Talbi, A; Ahmoum, H; Nouneh, K; Touhami, ME; Taibi, M; Matei, E; Enculescu, M; Pintilie, L
Published: NOV 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, DOI: 10.1007/s00339-021-05038-y
Cu-Fe-Sn-S have been electrodeposited on indium tin oxide coated glass (ITO/glass) substrates, varying only the deposition time, followed by sulfurization in argon atmosphere at a temperature of 500 degrees C. X-ray diffraction patterns confirmed the formation of polycrystalline CFTS and other secondary phases. The Raman spectroscopy results confirm the formation of stannite phase, by the existence of the most intense peak at 330 cm(-1) corresponding to A-symmetry vibrational mode, while the SnS2 surface phase reduces upon increasing deposition time. The inferred bandgaps by specular transmission are in 1.4-1.7 eV range, influenced by the detected orthorhombic Cu4SnS4 and rhodostannite secondary phases. The electrical measurements confirm the p-type nature of the films, while density of free carriers is relatively high (similar to 10(19) cm(-3)), leading to extremely low resistivity in the Omega cm range.
18. Towards phase pure kesterite Cu2ZnSnS4 absorber layers growth via single step free sulfurization electrodeposition under a fix applied potential on Mo substrate
Authors:
Azmi, S; Moujib, A; Layachi, OA; Matei, E; Galca, AC; Zaki, MY; Secu, M; Rusu, MI; Grigorescu, CEA; Khoumri, EM
Published: NOV 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 842, DOI: 10.1016/j.jallcom.2020.155821
This work presents a new synthesis and characterization of Kesterite Cu2ZnSnS4 films by one step electrodeposition with free sulfurization annealing treatment at different applied potentials. This study highlights the effect of applied potential and annealing treatment on the properties of CZTS deposited films. X-ray Diffraction and Raman spectroscopy were employed to assess the structure and composition of the films elaborated at -1V, -1.1V, and -1.2V vs Saturated Calomel Electrode (SCE). The morphological and optical properties were studied using Scanning Electron microscopy and photoluminescence spectroscopy (PL), respectively. The structural properties are improved by annealing treatment, while -1.1V vs SCE was found to be the optimum applied potential to prepare the Kesterite CZTS thin film with a bandgap around 1.5 eV. (C) 2020 Elsevier B.V. All rights reserved.
19. Influence of boric acid concentration on the properties of electrodeposited CZTS absorber layers
Authors:
Zaki, MY; Nouneh, K; Touhami, ME; Matei, E; Badica, P; Burdusel, M; Negrila, CC; Baibarac, M; Pintilie, L; Galca, AC
Published: MAY 2020, PHYSICA SCRIPTA, 95, DOI: 10.1088/1402-4896/ab6afd
This work involves the synthesis and characterization of Cu2ZnSnS4 (CZTS) layers. The films were prepared on Mo/glass substrates by single-step electrodeposition method followed by sulfurization at 500 degrees C under argon flow. The effect of boric acid concentration on the crystallographic structure, compositional and morphological properties of CZTS films was investigated, with the objective to understand the growth behavior and to enhance the film properties. Cyclic Voltammetry was used in order to estimate the adequate deposition potential for the CZT alloy. The x-ray diffraction analysis showed the formation of the kesterite phase in all the samples. The Raman and x-ray photoelectron spectroscopy studies confirmed the existence of the CZTS phase. The scanning electron microscopy was employed to inspect the films structure. The results indicated that increasing the concentration of boric acid affects the physico-chemical properties of the films.
20. Effect of mixing complexing agents on the properties of electrodeposited CZTS thin films
Authors:
Zaki, MY; Nouneh, K; Touhami, ME; Belakhmima, RA; Galca, AC; Pintilie, L; Enculescu, M; Baibarac, M; Taibi, M
Published: SEP 2018, OPTICAL MATERIALS, 83, 256, DOI: 10.1016/j.optmat.2018.06.030
This work involves the synthesis and characterization of Cu2ZnSnS4 (CZTS) layers. The films were prepared on ITO/glass substrate by ecofriendly and simple single-step electrodeposition method followed by sulfurization and annealing at 500 degrees C under Argon flow. By using two different complexing agents, the electrodeposition process can give better results. Therefore, the effect of combining the trisodium citrate - TC to multiple cornplexing agents (cetyl trimethyl ammonium bromide - CTAB, ethylene diamine tetra acetic acid - EDTA, Boric Acid - BA, Glutamic Acid - GA and Tartaric Acid - TA) is investigated. The characterization of the absorber films was done by X-ray diffraction (XRD) analysis, Raman spectroscopy, Scanning Electron Microscopy and Diffuse Reflectivity. The combination of TC and CTAB is suggested to be the best pair of complexing agents within the combinations used in this work.
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