Environment-friendly copper-based chalcogenide thin film solar cells: status and perspectives

Copper chalcogenides (CuCh) have attracted considerable attention due to their promising potential as environmental-friendly photoactive material for lightweight and flexible thin film solar cells. Further, CuCh can be fabricated from simple to complex chemical compositions and offer a remarkable charge carrier mobility and excellent absorption coefficient with a desirable bandgap (up to ∼1.0 eV). Currently, they have demonstrated maximum power conversion efficiencies of over 23% for single-junction, around 25% and 28% for monolithic 2-Terminal (2T) and mechanically-stacked 4-Terminal (4T) perovskite/CuCh tandem solar cells, respectively. This article presents an overview of CuCh-based materials, from binary- to quaternary-CuCh compounds for single- and multi-junction solar cells. Then, we discuss the development of fabrication methods and the approaches taken to improve the performance of CuCh-based thin film itself, including chemical doping, the development of complement layers, and their potential application in flexible and lightweight devices. Finally, these technologies' stability, scalability, and toxicity aspects are discussed to enhance their current marketability.

Metal-to-Semimetal Transition in Platinum Nanotubes: Dependence on Thickness

The temperature dependence of the electrical conductivity of Pt nanotubes (NTs) with different thicknesses synthesized by a wetting method using an Al₂O₃ membrane was studied. Pt NTs exhibited circular pores with an average diameter of ∼200 nm. From XRD, the prepared Pt NTs displayed a cubic crystal structure. Pt metal was identified based on the binding energy peak at 71 eV via XPS analysis. Pt NTs with thicknesses of 5 and 12 nm behaved like a semimetal, whereas Pt NTs with thicknesses of 25 and 29 nm showed normal metallic electrical conduction characteristics. This metal-to-semimetal transition was induced as the thickness and grain sizes of the Pt NTs were decreased. The critical metal-to-semimetal transition temperature of Pt NTs with average tube wall thicknesses of ∼5 nm was measured at ∼37 °C. However, the critical temperature could not be measured for NTs with a thickness of 12 nm. It is assumed that the critical temperature would be far below 0 °C. This transition behavior resulted from both a discontinuity in the density of states due to the quantum confinement effect and the increased energy barrier for conduction of electrons accompanied by the increased density of grain boundaries. These results presented here signify a vital step in the direction of realizing high-performance nanoelectronic devices.

Adsorption of Sr(II) ions and salicylic acid onto magnetic magnesium-zinc ferrites: isotherms and kinetic studies

Magnetic magnesium-zinc spinel ferrite Mg_1 - xZn_xFe₂O₄ (where x = 0.4, 0.6, and 0.8) was investigated as adsorbent for the efficient removal of Sr(II) ions and salicylic acid (SA) contaminants from aqueous medium. The characterization of ferrites was carried out using XRD, VSM, BET, SEM, and EDS. The surface charge of magnetic adsorbents was measured by the drift method. The determination of SA and Sr(II) ion concentrations in the solution phase was carried out by UFLC and complexometry, respectively. It was shown that varying of the Zn(II) content affected the adsorption capacities of magnesium-zinc ferrites. The increasing of zinc content from x(Zn²⁺) = 0.4 to x(Zn²⁺) = 0.6 increased the adsorption of Sr(II) ions from 50 to 65 mg/g, and then it was decreased to 36 mg/g for the sample with x(Zn) = 0.8. The Mg_0.4Zn_0.6Fe₂O₄ sample demonstrated the maximum adsorption capacity of 74 mg/g. The adsorption isotherm for Sr(II) was fitted by the Dubinin-Radushkevich, Langmuir, Freundlich, and Sips models. The adsorption kinetics of Sr(II) was analyzed by PFO, PSO, and Elovich models. The adsorption kinetics of SA was also investigated. It was demonstrated that the Mg_0.2Zn_0.8Fe₂O₄ sample exhibited 90% removal of salicylic acid from the water solutions. The results demonstrated that magnetic Mg-Zn ferrites with spinel structure are good sorbents for the removal of SA and Sr(II) ions from aqueous solution.