An all-sputtered photovoltaic ultraviolet photodetector based on co-doped CuCrO(2) and Al-doped ZnO heterojunction

Improvement of the photocatalytic activity of ZnO thin films doped with manganese

In the herein report, we synthesized ZnO thin films doped with manganese (Mn). We studied the impact of Mn doping loads (1 %, 3 %, 5 % wt.) on physicochemical properties of the compounds. Furthermore, we presented the photocatalytic efficiency in removal of methylene blue dye. The structural assay indicated ZnO conserve the wurtzite crystalline structure after dopant insertion. Furthermore, the crystalline size of catalysts was reduced after dopant incorporation. The SEM analysis showed a change in surface morphology after modification of ZnO thin films. Furthermore, Raman spectroscopy verified the Mn insertion inside the ZnO lattice. After the doping process, band gap was reduced by 16 %, in comparison to bare ZnO. After the photocatalytic test, the doped catalysts showed better performance than bare ZnO in removing MB. The best test showed a kinetics constant value of 2.9 × 10-3 min-1 after 120 min of visible irradiation. Finally, the Mn(5 %):ZnO thin film was suitable after five degradation cycles, and the degradation process efficiency was reduced by 32%.

Toward Industrial Production of a High-Performance Self-Powered Ultraviolet Photodetector Using Nanoporous Al-Doped ZnO Thin Films

Al-doped ZnO (AZO) thin films are effective n-type semiconductors for ultraviolet (UV) detection because of their low cost, high electron mobility, and high sensitivity to UV light, especially in the UVA spectrum. However, a reasonable compromise between performance (such as sensitivity, detectivity, and response time) and fabrication ease remains an obstacle to the practicability of AZO-based UV photodetectors. To address this issue, we propose an efficient strategy to achieve a large AZO photoactive area for outstanding performance, along with a facile sol-gel method. Consequently, the device exhibits a superb on/off ratio of >104, a high detectivity of 1.85 × 1012 Jones, and a fast response speed under 365 nm UVA illumination without external energy consumption. Hence, this study suggests a self-powered and high-performance nanoporous AZO-based UVA detector with an environmentally friendly scalable process that satisfies industrial production requirements for numerous practical UV-detection applications.

Investigating various metal contacts for p-type delafossite α-CuGaO2 to fabricate ultraviolet photodetector

Delafossite semiconductors have attracted substantial attention in the field of electro-optics owing to their unique properties and availability of p-type materials that are applicable for solar cells, photocatalysts, photodetectors (PDs) and p-type transparent conductive oxides (TCOs). The CuGaO₂ (CGO), as one of the most promising p-type delafossite materials, has appealing electrical and optical properties. In this work, we are able to synthesize CGO with different phases by adopting solid-state reaction route using sputtering followed by heat treatment at different temperatures. By examining the structural properties of CGO thin films, we found that the pure delafossite phase appears at the annealing temperature of 900 °C. While at lower temperatures, delafossite phase can be observed, but along with spinel phase. Furthermore, their structural and physical characterizations indicate an improvement of material-quality at temperatures higher than 600 °C. Thereafter, we fabricated a CGO-based ultraviolet-PD (UV-PD) with a metal-semiconductor-metal (MSM) configuration which exhibits a remarkable performance compared to the other CGO-based UV-PDs and have also investigated the effect of metal contacts on the device performance. We demonstrate that UV-PD with the employment of Cu as the electrical contact shows a Schottky behavior with a responsivity of 29 mA/W with a short response time of 1.8 and 5.9 s for rise and decay times, respectively. In contrast, the UV-PD with Ag electrode has shown an improved responsivity of about 85 mA/W with a slower rise/decay time of 12.2/12.8 s. Our work sheds light on the development of p-type delafossite semiconductor for possible optoelectronics application of the future.

Research advances in ZnO nanomaterials-based UV photode tectors: a review

Ultraviolet photodetectors (UV PDs) have always been the research focus of semiconductor optoelectronic devices due to their wide application fields and diverse compositions. As one of the best-known n-type metal oxides in third-generation semiconductor electronic devices, ZnO nanostructures and their assembly with other materials have received extensive research. In this paper, the research progress of different types of ZnO UV PDs is reviewed, and the effects of different nanostructures on ZnO UV PDs are summarized in detail. In addition, physical effects such as piezoelectric photoelectric effect, pyroelectric effect, and three ways of heterojunction, noble metal local surface plasmon resonance enhancement and formation of ternary metal oxides on the performance of ZnO UV PDs were also investigated. The applications of these PDs in UV sensing, wearable devices, and optical communication are displayed. Finally, the possible opportunities and challenges for the future development of ZnO UV PDs are prospected.

Photo-supercapacitors based on nanoscaled ZnO

In this study, zinc oxide (ZnO) powders in two different morphologies, nanowire (NW) and nanoflower (NF), have been synthesized by the hydrothermal method. The eligibility of the pristine ZnO nanopowders as a photo-active material has been revealed by designing P-SC devices via the facile drop-casting method on both glass and plastic substrates in large-area applications. The impact of physical properties and especially defect structures on photo-supercapacitor (P-SC) performance have been explored. Although the dark Coulombic efficiency (CE%) of both NW and NF-based P-SC were very close to each other, the CE% of NW P-SC increased 3 times, while the CE% of NF P-SC increased 1.7 times under the UV-light. This is because the charge carriers produced under light excitation, extend the discharge time, and as confirmed by electron paramagnetic resonance, photoluminescence, and transmission electron microscopy analyses, the performance of P-SCs made from NF powders was relatively low compared to those produced from NW due to the high core defects in NF powders. The energy density of 78.1 mWh kg⁻¹ obtained for NF-based P-SCs is very promising, and the capacitance retention value of almost 100% for 3000 cycles showed that the P-SCs produced from these materials were entirely stable. Compared to the literature, the P-SCs we propose in this study are essential for new generation energy storage systems, thanks to their ease of design, adaptability to mass production for large-area applications, and their ability to store more energy under illumination.

Doping-Dependent Optical Response of a Hybrid Transparent Conductive Oxide/Plasmonic Medium

Understanding the interaction between plasmonic nanoparticles and transparent conductive oxides is instrumental to the development of next-generation photovoltaic, optoelectronic, and energy-efficient solid-state lighting devices. We investigated the optical response of hybrid media composed of gold nanoparticles deposited on aluminum-doped zinc oxide thin films with varying doping concentration by spectroscopic ellipsometry. The dielectric functions of bare AZO were addressed first, revealing doping-induced effects such as the band gap shift and the appearance of free carriers. In the hybrid media, a blue-shift of the localized surface plasmon resonance of Au NPs as a function of increasing Al doping of the substrate was observed, ascribed to the occurrence of a charge transfer between the two materials and the doping-dependent variation of the polarizability of the substrate.

Fabrication of a UV Photodetector Based on n-TiO2/p-CuMnO2 Heterostructures

The heterojunction based on n-TiO2 nanolayer/p-CuMnO2 thin film was achieved using an efficient two-step synthesis process for the fabrication of a UV photodetector. The first step consisted of obtaining the TiO2 nanolayer, which was grown on titan foil by thermal oxidation (Ti-TiO2). The second step consisted of CuMnO2 thin film deposition onto the surface of Ti-TiO2 using the Doctor Blade method. Techniques such as X-ray diffraction, UV-VIS analysis, SEM, and AFM morphologies were used for the investigation of the structural and morphological characteristics of the as-synthesized heterostructures. The Mott–Schottky analysis was performed in order to prove the n-TiO2/p-CuMnO2 junction. The I-V measurements of the n-TiO2 nanolayer/p-CuMnO2 thin film heterostructure confirm its diode characteristics under dark state, UV and visible illumination conditions. The obtained heterojunction, which is based on two types of semiconductors with different energy band structures, improves the separating results of charges, which is very important for high-performance UV photodetectors.