CuO–ZnO nanocomposite films with efficient interfacial charge transfer characteristics for optoelectronic applications

Enhancing Photoelectric Response of Self-powered UV and Visible Detectors Using CuO/ZnO NRs Heterojunctions

Understanding the development and performance of UV photodetectors is crucial, given their extensive applications in both military and civilian sectors. The evolution of self-powered photodetectors, especially those based on heterojunction nanostructures, has demonstrated significant potential for enhancing both device efficiency and functionality. By exploring the effects of material composition and structural design, can optimize these devices for improved photoelectric response and energy efficiency. In this study, we prepared the CuO/ZnO NRs heterojunction photodetector on an ITO substrate to enhance photoelectric response of UV detectors. The fabrication process utilized the hydrothermal method and the spin coating technique. The effect of CuO concentration on the optical response of the photodetector under UV radiation at wavelengths of 405 nm and 385 nm was investigated. The samples were characterized using FESSEM, XRD, EDX, and UV-Vis spectra. The device is further distinguished by its standard I-V curves and photocurrent-time curves, which demonstrate the device's behavior under various light conditions. The prepared thin films are polycrystalline, with CuO layers displaying monoclinic phases and ZnO layers exhibiting a hexagonal wurtzite phase. All samples have the potential to exhibit photovoltaic properties and self-powered capabilities. Furthermore, the I-V curve confirms that the photocurrent mechanism of these junctions adheres to the recombination standard, in addition to demonstrating correction behavior. A sample with a CuO concentration of 0.1 M shows the highest photosensitivity, reaching 340,700%, and a photocurrent gain (Iph/Idark) of 3,408 when exposed to light irradiation at 405 nm. Additionally, it exhibits a rapid response time of 0.8 s.

Charge Steering in Heterojunction Photocatalysis: General Principles, Design, Construction, and Challenges

Steering charge kinetics is a key to optimizing quantum efficiency. Advancing the design of photocatalysts (ranging from single semiconductor to multicomponent semiconductor junctions) that promise improved photocatalytic performance for converting solar to chemical energy, entails mastery of increasingly more complicated processes. Indeed, charge kinetics become more complex as both charge generation and charge consumption may occur simultaneously on different components, generally with charges being transferred from one component to another. Capturing detailed charge dynamics information in each heterojunction would provide numerous significant benefits for applications and has been needed for a long time. Here, the steering of charge kinetics by modulating charge energy states in the design of semiconductor-metal-interface-based heterogeneous photocatalysts is focused. These phenomena can be delineated by separating heterojunctions into classes exhibiting either Schottky/ohmic or plasmonic effects. General principles for the design and construction of heterojunction photocatalysts, including recent advances in the interfacing of semiconductors with graphene, carbon quantum dots, and graphitic carbon nitride are presented. Their limitations and possible future outlook are brought forward to further instruct the field in designing highly efficient photocatalysts.

Synthesis and comparative study of the structural and optical properties of binary ZnO-based composites for environmental applications

The development of photoactive systems to solve serious environmental problems is a key objective of researchers and remains a real challenge. Herein, n-p heterojunction ZnO-based composites were developed to achieve better photocatalytic performance in methylene blue (MB) degradation under natural solar irradiation. The hydrothermal technique was used to synthesize zinc oxide (ZnO)/metal oxide (MO) composites, with a molar ratio of 1 : 1 (MO = Mn₃O₄; Fe₃O₄; CuO; NiO). Various characterization techniques were used for the analysis of the structural, morphological and optical properties. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) Diffuse Reflectance Spectroscopy analysis (DRS), and Diffuse Reflectance Spectroscopy analysis (DRS) validated the presence of two phases for each sample, excluding any impurities. Indeed, the ZnO structure was not affected by the coupling with MO, confirming that MO was well dispersed on the surface of the ZnO crystalline lattice for each composite. Eventually, the photocatalytic performance evaluation test of the synthesized photocatalysts was carried out on aqueous MB solution. According to the results, the ZnO/Fe₃O₄ nano-catalyst showed the best photodegradation efficiency. This result suggests that the formation of Fe₃O₄/ZnO as a p/n heterojunction reduces the recombination of photo-generated electron/hole pairs and broadens the solar spectral response range, resulting in significant photocatalytic efficiency. Meanwhile, the possible mechanism for degradation of the MB was discussed.

Composite formation in CdSe:Cu2Se nanocrystal films, charge transport characteristics and heterojunction performance

The use of nanocrystals as materials for potential technological applications depends on tailoring their properties through intentional doping with external impurities. We have used a new technique to synthesize nanocrystal thin films of CdSe:Cu₂Se containing different weight percentages (wt%) of Cu₂Se. The films were deposited on glass substrates at room temperature by co-evaporation of CdSe and Cu₂Se powder in nitrogen gas at a pressure larger than that required for conventional thin film deposition. The films consisted of nanograins of CdSe doped with Cu₂Se (i.e., nanograins of Cd_1−xCu_2(x)Se where x is the atom% of Cu₂Se doped into CdSe) for lower wt% of Cu₂Se, and nanocomposites of Cd_1−xCu_2(x)Se and Cu₂Se for higher wt% of Cu₂Se. An energy band diagram built using the Anderson model was used for discussing the heterojunction characteristics of the junction between nanograins of Cd_1−xCu_2(x)Se and Cu₂Se. To investigate the usefulness of the nanocrystal thin films of CdSe:Cu₂Se for practical applications, the I–V characteristics of p–p and p–n hetero-junctions formed by the films respectively with nanostructured films of similarly deposited Cu₂Se and CdSe films were studied.

The use of nanocrystals as materials for potential technological applications depends on tailoring their properties through intentional doping with external impurities.