On the identification of Sb2Se3 using Raman scattering

Robust evidences are presented that show that the Raman mode close to 250 cm-1 in Sb2Se3 thin films does not belong to this binary compound. A study of the Raman spectrum power dependency revealed the formation of Sb2O3 for high values of power excitation when these measurements are done in normal atmospheric conditions. In order to complement this study, Sb2Se3 thin films were annealed to mimic the thermal conditions of Raman measurements and characterized by X-ray diffraction technique. These measurements showed that the compound Sb2Se3 can be replaced by Sb2O3 under those conditions and a heat-assisted chemical process explains these findings. Furthermore, it is shown what the Raman conditions that are needed for correct measurements to be performed.publishe

Implementation of molecular modeling to investigate ion transportation in proton exchange membranes comprising graphene oxide and polyacrylate nanocomposites

Proton exchange membranes (PEMs) play a critical role in various energy conversion devices, such as fuel cells. Developing advanced PEMs with improved hydronium ion transportation and chemical stability is essential for enhancing the performance and durability of these devices. In this research project, we focus on the development and molecular modeling study of a novel composite material based on poly(acrylic acid) and graphene oxide for application as a high-performance proton exchange membrane. The need for better PEMs has led us to explore the potential of combining poly(acrylic acid) and graphene oxide, as both materials offer unique advantages in terms of proton conductivity and mechanical strength. Our goal is to investigate how these two components interact and synergize to enhance the overall performance of the PEM, particularly in challenging operating conditions. To achieve this, classical all-atom Molecular Dynamics (MD) simulations using Gromacs software were employed. The simulations allowed us to study the formation mechanism of the poly(acrylic acid) and graphene oxide composite material and its application in facilitating hydronium ion transportation within the PEM. Our simulation results revealed fascinating insights into the composite material's behavior. Notably, we observed the emergence of new interactions between poly(acrylate) oligomers and graphene oxide layers, evident from the analysis of interaction energy values. These interactions contribute to the material's enhanced transport properties, making it promising for PEM applications. Moreover, we assessed the mobility of hydronium ions in the graphene oxide and polyacrylate nanocomposite-based PEM and found it comparable to the mobility in traditional poly(acrylate)-based PEMs. This indicates that the introduction of graphene oxide provide compatible proton transport efficiency and renders the composite suitable for practical application in PEM devices. In conclusion, our study demonstrates the potential of the poly(acrylic acid) and graphene oxide composite as a high-performance proton exchange membrane

Phase selective growth of Cu12Sb4S13 and Cu3SbS4 thin films by chalcogenization of simultaneous sputtered metal precursors

In this work, it is presented a procedure to grow single phase Cu12Sb4S13 and Cu3SbS4 thin films consisting on the annealing of simultaneously sputtered metal precursors fllowed by a annealing treatment in a sulphur atmosphere. The selection of the ternary phase which is intended to grow is performed by adjusting the sulfur evaporation temperature in chalcogenization process. It is shown that for a sulphur evaporation temperature of 140 ◦C the predominant phase is Cu12Sb4S13 and for 180 ◦C the predominant phase is Cu3SbS4. In order to ensure precursor composition homogeneity, the Cu-Sb metallic precursors are deposited simultaneously by rf magnetron sputtering using adjustable segmented targets. The morphological characterization of the films was made by scanning electron microscopy and the composition was analysed by energy dispersive spectroscopy. The structural analysis and phase identification were performed by X-ray diffraction and Raman scattering. The optical properties were studied through spectrophotometry on films deposited directly on bare glass.publishe

Growth of Sb2Se3 thin films by selenization of RF sputtered binary precursors

In this work we present a method to grow Sb2Se3 thin films with a potential use as absorber layers in solar cell structures. The films were grown on several substrates: soda-lime glass, Mo coated soda-lime glass and Si . The Sb-Se precursor’s films were deposited by RF magnetron sputtering and then selenized under a H2Se gas flow. Different selenization temperatures were tested and analysed. Compositional and morphological analyses were performed by Energy Dispersive Spectroscopy and Scanning Electron Microscopy, respectively. Phase identification and structural characterization were done by X-ray Diffraction and Raman scattering spectroscopy showing that Sb2Se3 is the dominant phase with an orthorhombic crystalline structure. Traces of rhombohedral and amorphous Se secondary phases were also observed supported by their Se-rich compositions. Visible-NIR reflectance measurements allowed to extract a direct bandgap with a value close to 1.06 eV. Photoluminescence spectroscopy shows an emission with a broad band at 0.85 eV for samples selenized at lower temperatures and an intense peak at 0.75 eV for the sample selenized at higher temperatures. Electrical characterization shows low free hole concentrations and mobilities. At low temperatures, the nearest neighbour hopping is the dominant mechanism for the electronic transport for the analysed samples. Both electrical and optical properties are influenced by the type of defects present on samples. A discussion is made on the properties that need to be improved in order that these films can be integrated into thin film solar cells.publishe