A quantitative and analytical investigation on the conduction mechanism in p-type cuprous oxide (Cu2O) thin films is performed based on analysis of the relative dominance of trap-limited and grain-boundary-limited conduction. It is found that carrier transport in as-deposited Cu2O is governed by grain-boundary-limited conduction (GLC), while after high-temperature annealing, GLC becomes insignificant and trap-limited conduction (TLC) dominates. This suggests that the very low Hall mobility of as-deposited Cu2O is due to significant GLC, and the Hall mobility enhancement by high-temperature annealing is determined by TLC. Evaluation of the grain size and the energy barrier height at the grain boundary shows an increase in the grain size and a considerable decrease in the energy barrier height after high-temperature annealing, which is considered to be the cause of the significant reduction in the GLC effect. Additionally, the density of copper vacancies was extracted; this quantitatively shows that an increase in annealing temperature leads to a reduction in copper vacancies.

Controlling the electronic and photoexcited properties of cuprous oxide (Cu2O) through slight modifications of the synthesis method can impact a wide range of emerging technologies. Herein, we consider copper vacancies in Cu2O as a prototype of a p-type oxide semiconductor for studying the impact of crystal and electronic structure on carbon dioxide photoreduction. Oriented films of copper vacancy modulated Cu2O consisting of nano twin structures are electrodeposited by changing the potential in an aqueous alkaline copper(II)-lactate solution. The copper vacancies introduce tail states inside the band gap, improving the hole concentration and facilitating the charge separation and transfer in the Cu2O photocathode. This study gives an in-depth view of how a cation-deficient structure regulates and promotes photoelectrochemical activity toward CO2 reduction.

Absorbent materials are being developed to replace semiconductor materials such as p-type silicon, GaAs, CdTe, and quaternary compounds such as CIGS (copper indium gallium selenide). Cu2O is a potential candidate because it is non-toxic, inexpensive, an abundant compound in the Earth’s crust, and has good optical properties, such as a high absorption coefficient. In this work, Cu2O was obtained simply by reducing Benedict’s solution with glucose in an alkaline medium (pH 10.2 ± 0.2) at 65°C. The samples were synthesized by varying glucose content from 1 g to 7 g. The results showed a phase proportion variation between 95.56% and 99.50% of the Cu2O phase. It was found that the changes in crystallite size, microstrains, particle size, and morphology are due to reaction times, which were influenced by the use of different glucose amounts. The use of a higher glucose amount in the synthesis favors a faster reaction, forming smaller crystallites with more microstrains. Lower glucose amount leads to a slower reaction giving the crystallites more time to grow, which relaxes the microstrains. When increasing glucose content, the obtained morphologies changed from cubes, irregular cubes, prismatic spheres, cauliflower-like, to spherical shapes. The XPS spectra confirmed only the presence of chemical species such as Cu(I) and Cu(II), and chemical defects, such as oxygen vacancies (Vo), were detected in the samples. All samples presented a broad absorption range from 200 nm to 570 nm indistinctly of the morphology. The band gap showed an insignificant change from 2.04 eV to 2.09 eV when glucose was increased from 1 g to 7 g. The in-situ phase transformation study was analyzed from 25°C to 700°C. The results indicated a phase transition from Cu2O to Cu and CuO when the temperature was above 280°C.

Cuprous oxide (Cu2O) is a typical p-type oxide semiconductor with a bandgap of approximately 2.0 eV. Due to its suitable band position, it has become a promising photocathode material in the field of photoelectrochemical (PEC) water reduction. However, it faces critical challenges such as low charge separation efficiency and poor photocorrosion stability. Herein, we report a novel strategy combining physical magnetron sputtering and chemical electrodeposition to construct a Cu/Cu2O/TiO2 composite photocathode with a sandwich structure on FTO conductive glass. In this architecture, the metallic Cu interlayer serves a triple role: enhancing the substrate conductivity, providing nucleation sites to induce the preferential growth of Cu2O along the highly active (111) crystal plane, and simultaneously generating hot electrons via the surface plasmon resonance (SPR) effect to promote carrier generation. The dense TiO2 overlayer not only acts as a protective layer against photocorrosion but also forms a p-n heterojunction with Cu2O, establishing a built-in electric field that facilitates efficient spatial charge separation. The resulting Cu/Cu2O/TiO2 photoelectrode achieves a photocurrent density of -7.2 mA·cm-2 at 0 V vs. RHE, which is 1.57 and 1.33 times higher than those of pure Cu2O and Cu/Cu2O, respectively. Through band gradient modulation, this approach reduces charge transfer resistance and prolongs carrier lifetime, confirming the synergistic effects of the Cu SPR layer and

Cu 2 O thin film is a p-type oxide semiconductor which has a high absorption system, eco-friendly, resource-friendly material. So it can be used in various fields of optoelectronic devices such as solar cell absorption layers, water splitting device and photocathode materials of photovoltaic cells. The electrochemical deposition process of the Cu 2 O thin film that can be used as an optoelectronic device has advantages such as large-area deposition, precursor recycling function, low-cost process, and low-temperature deposition. This has industrial and economic competitiveness, which has a great advantage over conventional vacuum processing equipment. However, Cu 2 O thin films grown by using an electrochemical deposition method based on normal pressure and low temperature have lower conductivity than thin films grown by using a vacuum process. The efficiency of the device is inevitably lower than that of thin films based on vacuum process equipment because the electrons and holes cannot be effectively separated. In order to solve the conductivity problem of the thin film, various methods such as optimizing the deposition method and applying a post-deposition treatment process were conducted. The research team improved the mobility of the thin film in the (111) direction by dramatically inducing the preferential growth of the Cu 2 O thin film by adding Sb, which acts as a metal surfactant that can control the growth behavior. The charge separation was effectively confirmed by

The chemical and electronic properties of copper combined with its large natural abundance lend this material to impact a wide range of technological applications, including heterogeneous catalysis. The reactivity of copper in its Cu 1+ oxidation state makes this specific configuration relevant in various chemical reactions, but the facile redox properties of copper make the isolation of individual states for fundamental studies difficult. Here, in this study, we review three Cu 2 O model systems used to study the interaction of Cu 1+ with small molecules making use of surface science techniques: Cu 2 O/Cu(111), thin polycrystalline Cu 2 O films on Cu foil, and bulk Cu 2 O crystals. Advantages and disadvantages of each system are discussed and exemplified through case studies of chemical adsorption and reactivity studies.