K A Jagadish

This study investigates copper oxide thin films, deposited by reactive DC magnetron sputtering at room temperature, for use as absorber layers in thin‐film solar cells. Films are synthesized under varying oxygen flow rates (16–33%). Structural analysis (X‐ray diffraction, Raman) reveals a phase transition from mixed Cu ₄ O ₃ CuO to phase‐pure monoclinic CuO at 23% oxygen, correlating with enhanced crystallinity. Atomic force microscope shows oxygen flow‐influenced film morphology, correlating with crystallite growth. Optical properties vary with oxygen flow: lower flows improve absorption, while higher flows increase transmittance, indicating reduced defect density. The optical bandgap ranges from 1.73 to 1.98 eV in line with phase changes. X‐ray photoelectron spectroscopy further confirms the presence of Cu ₄ O ₃ at low oxygen flows and CuO at high oxygen flows, validating the observed phase evolution. Hall measurements demonstrate that oxygen flow significantly tunes the electrical properties, with optimal values observed at 23–28% oxygen. Using these parameters, SCAPS‐1D simulations of TiO ₂ /CuO solar cells predict a 22.8% power conversion efficiency and 89.3% fill factor for a 5 μm CuO layer with a 1.73 eV bandgap. Overall, the findings demonstrate the precise control over CuO thin film properties through oxygen flow tuning, underscoring their considerable potential for high‐efficiency solar energy applications.

This study investigates the AC electrical properties of Cu₂O/TiO₂ heterojunctions deposited via reactive DC magnetron sputtering, with a focus on the role of interfacial dynamics and post-deposition annealing. Mott–Schottky analysis revealed built-in potentials ranging from 0.45 V to 1.92 V, with carrier concentrations between 1.43 × 10¹⁶ and 9.93 × 10¹⁶ cm⁻³, influenced by the annealing temperature. The depletion width was estimated to be roughly 395 nm in the 150 °C annealed samples, and the TiO₂ layer was more depleted across all samples. Dielectric constant (ε′) values decreased from approximately 85 to about 10 as frequency increased from 1 kHz to 1 MHz, while tangent loss also diminished significantly, indicating reduced dipolar and space-charge polarization. The imaginary part of the dielectric constant (ε″) confirmed strong interfacial polarization at low frequencies. AC conductivity rose with frequency, supporting a thermally activated hopping conduction mechanism. Impedance spectroscopy, modelled with an R(CR)(QR)(CR) circuit, exhibited multiple relaxation behaviors, and incorporating a constant phase element (CPE) accounted for non-ideal dielectric effects caused by surface inhomogeneity. Rapid thermal annealing resulted in a decrease in series resistance, from 844 Ω at room temperature to 802 Ω at 150 °C. Annealing at 150 °C produced optimal outcomes, reducing interface losses and enhancing charge transport. These findings underscore the tunability and potential of Cu₂O/TiO₂ heterostructures for optoelectronic applications such as photodetectors and solar cells.

In this study, we present a comprehensive investigation into the impact of combined oxygen and argon flow rates on the physical properties of Cr₂O₃ thin films produced via reactive DC magnetron sputtering. Additionally, we explore the influence of oxygen flow rate on various aspects, including structural, morphological, optical, chemical, and electrical characteristics of the sputtered Cr₂O₃ thin films. Our analysis, based on XRD results, reveals the polycrystalline nature of the films. Surface morphology was examined through scanning electron microscopy. Optical analysis indicates a band gap ranging from 2.70 eV to 2.99 eV for the films. X-ray photoelectron spectroscopy analysis shows the splitting of Cr 2p core spectra into Cr 2p_3/2 and Cr 2p_1/2 domains within the range of 573 eV to 585 eV, alongside the presence of satellite peaks. Moreover, extracted electrical properties reveal the p-type conductivity of the deposited Cr₂O₃ thin film under various oxygen flow rates. Furthermore, we fabricate and characterize an ITO/p-Cr₂O₃/Al Schottky diode to provide additional insights into p-Cr₂O₃/Al Schottky diodes. Overall, this study contributes valuable insights and enhances our understanding of Cr₂O₃ thin film properties, particularly in the context of semiconductor devices like Schottky diodes.