Search Results (538)

Graphene oxide (GO) and reduced graphene oxide (rGO) are widely studied two-dimensional carbon nanomaterials for optoelectronic devices. Because the oxygen content and degree of reduction govern the electronic structure of GO-derived films, controlling the reduction process is essential for tailoring their properties. Laser-induced reduction provides a tunable, contact-free route to transparent and conductive graphene-based layers. In this work, 80 nm spray-coated GO layers were reduced using a KrF excimer laser (248 nm, 20 ns) at a fluence of 20 mJ cm⁻², while systematically varying the number of laser pulses (LP) from 1 to 1000. We tuned the degree of GO reduction by stepwise increasing the number of LP and followed the resulting changes in surface composition using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. The surface composition evolves non-monotonically with the number of laser pulses, revealing a multi-step reduction mechanism. At low laser doses, epoxide groups are preferentially removed or converted, generating a more disordered distribution of hydroxyl-containing sites on the GO sheets. At intermediate laser doses, oxygen-containing groups are depleted, and sp² conjugation is restored. After extended irradiation in air, however, oxygenated surface species partially re-form. Conductivity measurements show that the sheet resistance reaches a minimum at approximately 300 LP, consistent with efficient chemical reduction and recovery of the conjugated carbon network. These results provide molecular-level guidelines for optimizing laser-induced GO reduction toward graphene-based transparent conductive layers. Full article

In the present work, graphene-modified zinc oxide (ZnO-rGO) and fluorine-doped tin oxide (FTO) thin films were successfully fabricated using a simple, low-cost pulsed spray pyrolysis technique. The structural, morphological, optical, electrical, and surface electronic properties of the deposited films were systematically characterized. X-ray diffraction (XRD) analysis confirmed the formation of polycrystalline ZnO- and SnO₂-based phases with crystallite sizes in the nanometer range. The crystallographic parameters, microstrain, and dislocation density of the deposited films were found to be influenced by the incorporation of reduced graphene oxide (rGO) and fluorine dopants. Scanning electron microscopy (SEM) revealed compact and homogeneous surface morphologies with good film coverage and well-defined nanocrystalline features. Optical characterization demonstrated the wide-bandgap semiconducting behavior of the deposited films, with optical bandgap energies ranging from 3.262 to 3.312 eV for the ZnO-rGO films and from 3.91 to 4.01 eV for the FTO films. Kelvin probe measurements yielded work-function values in the range of approximately 5.0–5.2 eV, indicating favorable surface electronic characteristics suitable for optoelectronic applications. Furthermore, fluorine incorporation enhanced the dielectric response of the SnO₂ films, particularly in the low-frequency region owing to increased interfacial polarization effects. The obtained results demonstrate that pulsed spray pyrolysis provides a simple, cost-effective, and efficient route for fabricating ZnO-rGO and FTO thin films with desirable structural, optical, electrical, and surface electronic properties. These findings highlight the considerable potential of the developed materials for transparent electrodes and a wide range of optoelectronic applications. Full article

Spray pyrolysis is a popular method for the low-cost synthesis of oxides and other compounds in thin-film form. Here, we discuss several nuances of using this method for ternary and quaternary compounds. Specifically, we outline how precursor solubility and thermal decomposition, as well as desorption of intermediate species from the sample surface govern the spray pyrolysis growth process. We demonstrate how the stoichiometry transfer from solution to film can be affected in selected test cases. We present real-time optical growth measurements of the behaviour of individual Cu, Cr, Zn, and Sn precursors, as well as post-growth analysis of film composition by X-ray photoelectron spectroscopy for ternary transparent conducting oxides (TCOs; p-type: Cu_xCrO₂, SnTiO_x; and n-type: a-ZnSnO₃). We illustrate how several steps of spray pyrolysis affect the stoichiometry transfer from the solution to the ternary thin film. Using binary Cu₂O as a test case, we also show how the choice of instrument geometry and nozzle type can affect film homogeneity. All materials discussed have been chosen to highlight potential difficulties of the spray pyrolysis process of ternary, quaternary, or even more complex oxides, and the mechanisms should be considered for other materials as well. We therefore also provide an extensive overview of suitable precursor salts with similar expected properties as used in this experimental work to guide future ternary oxide studies. Full article

Flexible organic solar cells (FOSCs) are a promising green energy technology due to their mechanical flexibility, light weight, low cost, and compatibility with large-area solution processing. Although the power conversion efficiency (PCE) of rigid organic solar cells has exceeded 20%, a significant performance gap remains for flexible devices, primarily constrained by the limitations of two key components: the flexible substrate and the transparent electrode. This review systematically summarizes recent research progress on flexible substrates, including ultrathin glass, polymer substrates, stretchable substrates, and bio-based substrates, and flexible transparent electrodes, including ITO, conductive polymers, carbon-based nanomaterials, ultrathin metal films, metal grids, and metal nanowire networks. Building on this, the review explores strategies for the synergistic design of substrates and electrodes, analyzing critical pathways for their co-optimization across four dimensions: interface engineering, mechanical compatibility, optical coupling, and process integration. Examining representative case studies from the literature, optimal substrate–electrode pairings for different application scenarios are summarized. Finally, the review outlines a future perspective on the evolution from compatibility toward functional integration, offering a systematic framework for the development of next-generation flexible photovoltaic devices that are efficient, stable, and adaptable to diverse application requirements. Full article

Cadmium sulfide has been widely used as a conventional n-type window/buffer layer or heterojunction partner in several p-type thin-film solar cells, including CdTe/CdSeTe-, chalcopyrite-, kesterite-, antimony chalcogenide-, tin sulfide- and iron pyrite-based devices. Its success is related to its ability to form suitable heterojunctions, partially passivate absorber surfaces and provide favorable electronic selectivity. However, the parasitic absorption associated with the relatively narrow band gap of CdS, the toxicity and waste-management issues related to cadmium-containing auxiliary layers and the need for improved band alignment have motivated extensive research on CdS-free window and buffer layers. This review summarizes the main efforts devoted to replacing CdS in thin-film solar cells based on absorbers such as CdTe/CdSeTe, CIS, CIGS, CZTS, CZTSe, CZTSSe, Sb₂S₃, Sb₂Se₃, Sb₂(S,Se)₃, SnS and FeS₂. The most investigated alternative materials, including Zn(O,S), ZnS, In₂S₃, ZnMgO, ZnSnO, TiO₂, SnO₂ and SnS₂, are discussed with emphasis on their optical properties, band alignment, interface quality, deposition methods and impact on device performance. The analysis highlights that CdS replacement cannot be treated as a universal material substitution problem. Instead, each absorber and device architecture requires a specific front-interface design, where chemical compatibility, conduction band offset, defect passivation, optical transparency and process-induced interfacial modifications play a decisive role. CdS-free approaches are relatively mature for CdTe/CdSeTe- and CIGS-based solar cells, whereas kesterite absorbers, antimony chalcogenides and SnS still require further interface engineering. In FeS₂, by contrast, buffer-layer substitution remains secondary to the control of intrinsic surface and bulk electronic defects. This review provides a concise comparison of the most relevant CdS-free front/window materials and identifies key challenges for the future design of sustainable thin-film solar cells. Full article

In the present paper, we studied the interaction of microwave radiation with conductive indium tin oxide (ITO) coatings deposited on a borosilicate glass. The experiments were carried out with the ITO films, the thickness of which varied in the range from 85 to 607 nm. The transmittance and reflectivity of the ITO film/K108 glass structures were measured in the frequency region from 3 to 23 GHz. Theoretical modeling of the spectra was performed by means of the transfer matrix method. It was shown that for a given thickness of the glass substrate, the transmission and reflection spectra of the ITO film/K108 glass structures were fully determined by only one parameter of the ITO film, namely, its DC sheet resistivity. The considered model predicts an increase in maximum microwave shielding effectiveness up to 45.6 dB with a decrease in DC sheet resistivity to 1 Ohm/sq. ITO coatings with DC sheet resistivities down to 2.3 Ohm/sq have been experimentally investigated. The model microwave transmittance and reflectivity spectra were in good agreement with the experimental ones. In particular, the coefficient of determination for the transmittance spectra was rather high: R² > 0.93. It was experimentally demonstrated that applying antireflective coatings on both sides of the ITO film/K108 glass microwave shielding filter significantly improved its transparency in the operating optical range. A filter has been created that provides microwave shielding effectiveness of 38.7 dB with an average transmission coefficient of 0.81 in the visible range. Full article

Monitoring ultraviolet (UV) radiation dose distribution is crucial in many fields, like medicine and materials science, but traditional point-of-care methods limit the ability to fully assess the spatial extent of the irradiated surface. This paper presents the characterisation of a two-dimensional (2D) dosimetry system based on Pluronic F-127 hydrogel matrix doped with 2,3,5-triphenyltetrazolium chloride (TTC) with respect to exposition to UVA radiation. The hydrogel matrix (25% w/w) provides both high transparency and mechanical stability, while TTC (0.1% w/w) functions as a colour precursor that undergoes irreversible reduction to form water-insoluble red formazan upon UVA exposure. The insolubility of TTC formazan ensures that the resulting colour changes remain spatially stable within the dosimeter. The study included sample preparation in flat PMMA containers and analysis of the effect of radiation field uniformity in a UVP CL-1000 exposure chamber. It was supported by application of Kodak X-Omat 100 NIF UV Film dosimetry. The actual dose distribution in the chamber was shown to be significantly heterogeneous (CV coefficient of variation of approximately 18%), which emphasises the need for 2D dosimeters for precise validation of irradiation devices. The use of flatbed scanning and dedicated image analysis software allowed obtaining precise 2D dose distribution maps. The dosimeter was characterised in the dose range of 0–5000 mJ/cm², showing a reproducible response (R² = 0.9967). A resolution test was conducted to assess the precision of geometric representation. In the final stage of the study, the suitability of the developed dosimetry system was verified under conditions simulating heterogeneous UV radiation dose distribution using patterns printed with Computer-to-Film (CtF) technology. The results showed that optical effects in printed films significantly affect UV transmission, limiting accurate dose recording for black coverage above approximately 40–50%. The results obtained confirm that the TTC-Pluronic F-127 system is an effective, simple and low-cost tool for 2D monitoring of UVA radiation, with potential applications in cosmetology, dermatology, and material ageing tests. Full article

Copper (Cu) thin films and meshes on polyethylene terephthalate (PET) substrates are promising flexible transparent conductive electrodes (TCEs), yet their practical use is limited by insufficient interfacial adhesion and poor oxidative stability on inert polymer substrates. This work addresses these issues via a synergistic strategy of interfacial layer engineering and maskless laser lithography-based aperiodic mesh patterning, systematically comparing ceramic (Al₂O₃) and metallic (NiCr) interfacial layers for PET-supported Cu films and fabricating Linear/Sinusoidal aperiodic Cu meshes with tailored performance. Magnetron sputtering shows that Ar plasma-activated NiCr interfacial layers form a gradient-alloyed interface with Cu via interdiffusion, achieving 5B-level adhesion, mitigating bending-induced stress concentration, and enhancing damp-heat resistance (85 °C/85% RH) by suppressing oxidation—outperforming brittle Al₂O₃ layers. Patterning the optimized Cu/NiCr/PET structure into micrometer-scale meshes yields a Linear design with superior optoelectronic performance (~10.8 Ω/sq sheet resistance, >87% transmittance at 550 nm) and a Sinusoidal design with enhanced bending robustness via stress delocalization. Microstructural and elemental analyses clarify the NiCr layer’s interfacial toughening and anti-oxidation mechanisms. Practical validation in flexible transparent heaters demonstrates rapid thermal response and >20 h continuous operational stability. This study provides a scalable design strategy for high-performance PET-supported Cu meshes, offering insights for interface and structural optimization of flexible metallic TCEs for next-generation optoelectronics. Full article

Flexible transparent conductive films (TCFs) and their applications have attracted extensive interest. Silver nanowires (AgNWs) have been explored to replace conventional indium tin oxide (ITO) due to their high optical transmittance and superior electrical conductivity. Nevertheless, AgNWs tend to oxidize under ambient conditions, which weakens the conductive network and limits long-term performance. Spraying reduced graphene oxide (rGO) can stabilize the conductive network and inhibit oxidation, thereby enhancing the overall properties of the films. In this work, rGO/AgNW/PET TCFs were prepared using a spray-coating approach. The transmittance of the rGO/AgNW/PET TCFs was measured at 77% at 550 nm, accompanied by a sheet resistance of 6.8 Ω/sq. The films achieved the surface temperature of 95 °C at 6 V with stable operation while also achieving an electromagnetic interference shielding effectiveness of 27 dB. This structural design improves both performance and stability, offering great potential for flexible TCFs in advanced optoelectronic applications. Full article

Sodium-ion-based polymer electrolytes have emerged as an essential technology for the next generation of solid-state batteries, offering the possibility of greater safety and mechanical flexibility. This work aimed to prepare eco-friendly ormolytes based on a biohybrid host matrix, which were doped, for the first time, with a wide range of NaTFSI concentrations. The matrix consists of short poly(ε-caprolactone) segments covalently bonded to siliceous domains via urethane linkages. The samples obtained were thin and transparent films. They were characterized by means of thermogravimetric analysis (TGA) and X-ray diffraction (XRD), and the films exhibited an amorphous character over the entire composition range. Ionic conductivity measurements were performed, and at room temperature for n = 10, the ionic conductivity was 2.44 × 10⁻³ mS.cm⁻¹. The highest ionic conductivity value of 1.78 × 10⁻² mS.cm⁻¹ (n = 10) was obtained at 62.0 °C. To access the cation/urethane interactions, Fourier transform infrared (FT-IR) spectroscopy was employed, and it was noted that the global profile was slightly altered with the incorporation of salt, in which more interactions were observed for the more concentrated samples. Thus, the proposed material may be promising in the development of more sustainable and environmentally friendly electrochemical devices with Na ions. Full article

Multijunction solar cells employing a GaInP/GaAs/Ge triple-junction configuration are the dominant technology for space photovoltaic applications. The choice of an efficient electrode is crucial in solar cells, as it enables effective charge carrier collection and transport while allowing maximum light to reach the active layer. Indium tin oxide (ITO)/graphene hybrid electrodes have emerged as smart transparent conductors offering significant advantages over conventional brittle ITO films. Graphene electrodes were prepared by cold-wall chemical vapor deposition and ITO electrodes were commercially obtained and used as a base for hybrid ITO/graphene electrodes. Raman spectroscopy confirmed the successful integration and characteristic G and 2D bands on the ITO surface. Nanoscale current mapping via Tunneling Atomic Force Microscopy (TUNA-AFM) verified continuous conductive pathways throughout the film with ~60% increase in nanoscale tunneling current at graphene/ITO interfaces, indicating improved local charge transport pathways. These results demonstrate the suitability of ITO/graphene hybrid electrodes a promising material for multijunction solar cells and other aerospace technologies. Full article

Carbon nanotube (CNT) materials exhibit ultrahigh electrical and thermal conductivity. Upon electrical excitation, CNT-based transparent conductive films (TCFs) can emit far-infrared radiation (FIR) and provide certain physiotherapeutic efficacy, making them ideal candidates for thermotherapy applications. This work systematically tests and analyzes the fundamental physical properties and physiotherapeutic performance of CNT flexible thin-film heaters (TFHs) for potential use in health physiotherapy. Two types of TFHs with different electrode connection modes were fabricated via the prepared TCFs. Experimental characterizations were conducted on their response time, electrothermal performance, and heat transfer characteristics. The results showed that the temperature rise per unit input power for TFH1 was 16.71 °C/W, while that of TFH2 was 4.29 °C/W at the same voltage of 10 V. In addition, the variation trends of maximum temperature with power density were highly consistent for the two films. This demonstrates that TFHs fabricated using the same TCFs exhibit excellent and high electrothermal conversion efficiency as well as outstanding comprehensive electrothermal performance. In addition, smaller L/W ratio leads to lower resistance of TFHs, resulting in a stronger thermal effect under identical applied voltage. After the temperature stabilized, the surface temperature of the TFHs decreased by approximately 5 °C when attached to the human arm, confirming that the heat generated by the TFHs under electrical excitation could be effectively absorbed by the human body. The TFHs emitted rapid FIR upon electrification, and the peak wavelength ranged from 8 to 12 µm, which fell within the range of 6–14 µm that was easily absorbable by the human body. The heat can be rapidly absorbed by the skin and distributed throughout the body via blood circulation, yielding favorable physiotherapeutic efficacy. This study provides key physical parameters for the application of TFHs in wearable medical devices and physiotherapy equipment. Full article

Mine rescue operations are frequently conducted in hazardous underground environments characterized by damaged infrastructure, unstable communications, heat stress, and hypoxia risk, all of which threaten the safety of rescue personnel. To address these challenges, this study proposes a prototype-oriented mine-rescue monitoring framework that combines a Wi-Fi/optical-fiber communication architecture with flexible wearable sensing modules for physiological monitoring. The communication design employs Wi-Fi for local wireless data aggregation and optical fiber for reliable long-distance backhaul to the surface command side. For wearable monitoring, two flexible sensing modules were developed: a temperature sensor based on a polyaniline/graphene–polyvinyl butyral composite film and a PPG-oriented flexible optoelectronic module based on an ITO/Ag/ITO multilayer transparent electrode structure. Experimental results show that the temperature sensor exhibits a clear temperature-dependent resistance response within the tested range, while the optoelectronic module demonstrates low sheet resistance and acceptable electrical continuity under repeated bending. These results provide preliminary support for combining hybrid underground communication architecture with flexible wearable sensing components in mine-rescue scenarios. However, the present work remains at the stage of architecture design and component-level validation, and full end-to-end system verification under simulated or field rescue conditions will be the focus of future studies. Full article

Zinc oxide (ZnO) is currently one of the most significant wide-bandgap semiconductor materials, attracting extensive research across diverse fields including materials science, chemistry, physics, medicine, electronics, and power engineering. Its exceptional properties, such as high optical transparency, high electron mobility, chemical stability, and compatibility with low-cost fabrication techniques, have established ZnO as a versatile material with immense application potential. A critical application for ZnO is its role as a transparent conducting oxide (TCO) in modern optoelectronic and photovoltaic devices, as well as in sensors, transparent electronics, and spintronics. To meet the requirements of these advanced applications, precise control over the structural, optical, and electrical properties of ZnO thin films is essential. This is effectively achieved through the selection of specific synthesis methods and intentional modification techniques, such as doping. This review provides a comprehensive overview of the synthesis and modification of ZnO thin films, with a particular focus on how various dopants influence their fundamental characteristics. The work discusses a range of deposition techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), sol–gel methods, spray pyrolysis, and other solution-based approaches. The novelty of this review lies in its comparative analysis of different doping strategies combined with various thin-film deposition techniques, highlighting how specific synthesis routes influence dopant incorporation and ultimately determine functional properties. Furthermore, recent advances in tailoring ZnO thin films are summarized, alongside the identification of key challenges and future research directions. Ultimately, this work aims to provide researchers with a systematic perspective on the synthesis–structure–property relationships in doped ZnO thin films to support the development of optimized materials for next-generation electronic and optoelectronic devices. This review, thus, serves as a comprehensive reference for researchers and engineers seeking to optimize the functionality of ZnO-based thin films for emerging technological applications. Full article

In this study, a non-typical luminescent organosilicone was synthesized through a click reaction and used as a cross-linker to cure hydroxyl-terminated dimethylsilicone oil at room temperature via the sol–gel process, followed by application as a coating on a glass surface. This organosilicone film functions effectively as a luminescent down-shifting (LDS) material. Additionally, the presence of methyl groups and voids in the structure imparts a low refractive index, allowing it to serve as an anti-reflective (AR) layer. Optical and structural analyses on organosilicone-coated glass samples were conducted, and the dual-functional layer was applied to the glass cover of a perovskite solar panel to evaluate its performance. The coating not only enhanced light transmission as an AR layer but also converted UV light into blue light, which was absorbed by the solar cell. The results indicated improved solar panel performance, particularly in short-circuit current (Isc), external quantum efficiency (EQE) in the UV wavelength range, and overall efficiency. Overall, this material is a promising candidate for solar panel applications owing to maximized UV absorption for LDS, preserved transparency of the top cover glass, and room-temperature gelation, which facilitates repair of the dual-functional coating. Full article