Advanced Functional Nanostructured Films and Coatings for Energy Applications, 2nd Edition

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: 31 May 2026 | Viewed by 13547

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Institute for Polymers, Composites and Biomaterials (IPCB-CNR), National Research Council, Piazzale E. Fermi 1, 80055 Portici, Italy
Interests: functional materials; graphene; nanocomposites; polymer-embedded nanostructures
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Special Issue Information

Dear Colleagues,

At present, the topic of energy represents a real emergency for humankind, and therefore must be considered a priority in scientific research. The natural resources of energy are not inexhaustible, and the use of those more immediately accessible (i.e., fossil fuels) is not free of drawbacks such as environmental pollution. Energy is required in any industrial/domestic technology, and, consequently, finding a solution for these energy needs is a matter of universal relevance. Material science plays a key role in this process of renewing the type of energy resources we can exploit. The direct transformation of matter to energy, since it is based on a chemical reaction, inevitably produces byproducts, and therefore always has a high environmental impact. Conversely, the energy transduction (i.e., transformation from one form to another one) is based exclusively on physical phenomena, meaning it does not generate chemical byproducts and could be a technological solution worth studying. Advanced materials surely have a strategic role in this energy transition process. Physical phenomena always occur at interfaces between different solid phases. Interfaces have a key role because their extension only amplifies the physical phenomenon. Finally, surfaces, interfaces, coatings, and thin films will have a significant role in this energy transition. For these reasons, we propose a Special Issue highlighting the overlap among energy-related issues, surface science/technology, and nanostructuration

Dr. Gianfranco Carotenuto
Guest Editor

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Keywords

  • advanced energy materials
  • functional materials
  • nanocomposites
  • nanostructured materials
  • smart materials
  • polymeric coatings
  • hybrid coatings

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Related Special Issue

Published Papers (10 papers)

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Research

19 pages, 8216 KB  
Article
1 μm C-Doped GaN Thin Buffer on Sapphire with >3 kV Lateral Breakdown Voltage Grown by MOCVD
by Yitian Zhang, Xianfeng Ni, Qian Fan and Xing Gu
Coatings 2026, 16(5), 594; https://doi.org/10.3390/coatings16050594 (registering DOI) - 13 May 2026
Viewed by 116
Abstract
Sapphire-based GaN buffers face inherent challenges from the lattice mismatch between GaN and sapphire, which leads to high threading dislocation density and limits lateral breakdown voltage. In this work, we investigated the optimization of metal–organic chemical vapor deposition (MOCVD) growth parameters—specifically carbon doping [...] Read more.
Sapphire-based GaN buffers face inherent challenges from the lattice mismatch between GaN and sapphire, which leads to high threading dislocation density and limits lateral breakdown voltage. In this work, we investigated the optimization of metal–organic chemical vapor deposition (MOCVD) growth parameters—specifically carbon doping concentration, GaN buffer thickness, AlN nucleation layer thickness, growth pressure and V/III ratio—to enhance crystal quality and breakdown performance. A sapphire-based C-doped GaN buffer layer was successfully fabricated exhibiting a lateral breakdown voltage exceeding 3000 V across a 30 μm electrode gap corresponding to an average breakdown electric field of approximately 1.0 MV/cm, accompanied by low threading dislocation density, excellent surface roughness and low leakage currents. This study provides technical insights and practical growth guidelines for high-voltage sapphire-based GaN buffer layers, establishing the material basis for future high-voltage power device applications. Full article
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16 pages, 7426 KB  
Article
Mg Doping Gradient Engineering by MOCVD for Threshold Voltage Enhancement in Si-Based p-GaN E-Mode HEMTs
by Changyao Chen, Shuhan Zhang, Qian Fan, Xianfeng Ni and Xing Gu
Coatings 2026, 16(4), 476; https://doi.org/10.3390/coatings16040476 - 16 Apr 2026
Viewed by 480
Abstract
The threshold voltage (Vth) of p-GaN gate enhancement-mode (E-mode) high electron mobility transistors (HEMTs) on silicon substrates grown by metal–organic chemical vapor deposition (MOCVD) is often limited to 1.0–1.5 V. Apart from the low Mg acceptor activation rate, the non-uniform vertical Mg distribution [...] Read more.
The threshold voltage (Vth) of p-GaN gate enhancement-mode (E-mode) high electron mobility transistors (HEMTs) on silicon substrates grown by metal–organic chemical vapor deposition (MOCVD) is often limited to 1.0–1.5 V. Apart from the low Mg acceptor activation rate, the non-uniform vertical Mg distribution in thin p-GaN layers is also a key bottleneck limiting Vth. This work reveals that the vertical distribution (not only magnitude) of Mg doping fundamentally influences Vth by modulating the charge centroid and electric field coupling to the heterointerface. Through bis(cyclopentadienyl)magnesium (Cp2Mg) flow modulation, surfactant-assisted growth, and growth rate adjustment, the vertical Mg doping uniformity within the 80 nm p-GaN layer was improved while effectively suppressing Mg out-diffusion. A short-cycle gate-first self-aligned process was used to fabricate the devices, and the results showed that the improved Mg vertical distribution led to a significant Vth enhancement by 0.75 V. Technology Computer-Aided Design (TCAD) simulations further demonstrated that the uniform doping profile builds a stronger negative space charge field beneath the gate, raising the energy band and increasing Vth. This work not only presents practical strategies, but also establishes a direct physical link between vertical Mg doping distribution and Vth in Si-based E-mode HEMTs. Full article
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14 pages, 2094 KB  
Article
Grazing-Incidence SEM Characterization of MoS2 Nanosheet Coatings Prepared by Liquid-Phase Exfoliation
by Mariano Palomba, Francesca Nicolais, Filippo Giubileo, Antonio Di Bartolomeo, Gianfranco Carotenuto and Angela Longo
Coatings 2026, 16(3), 285; https://doi.org/10.3390/coatings16030285 - 27 Feb 2026
Viewed by 621
Abstract
Ultrathin two-dimensional (2D) coatings exhibit functional properties that are strongly defined by morphological features such as sheet edges, fracture sites, overlaps, folds, and local thickness variations, which are often difficult to resolve using conventional scanning electron microscopy (SEM) configurations. Here, we introduce a [...] Read more.
Ultrathin two-dimensional (2D) coatings exhibit functional properties that are strongly defined by morphological features such as sheet edges, fracture sites, overlaps, folds, and local thickness variations, which are often difficult to resolve using conventional scanning electron microscopy (SEM) configurations. Here, we introduce a grazing-incidence SEM approach based on controlled sample tilting close to 90° for enhancing surface sensitivity and morphological feature detectability in ultrathin coatings. The method is proved on colloidal MoS2 nanosheet coatings prepared by liquid-phase exfoliation. Optical absorption spectroscopy confirms the presence of mono- and few-layer MoS2 nanosheets in the dispersion, confirming the ultrathin nature of the deposited coating. Compared to standard 0° imaging, grazing-incidence SEM reveals clearer boundaries and discontinuities. Quantitative Sobel-based image analysis supports these observations, showing an increase in edge density from 5.9% to 7.6% and in average gradient magnitude from 0.151 to 0.172 a.u. under grazing incidence, indicating a higher amount of retrievable morphological information. The proposed approach relies only on standard stage tilting and provides a broadly applicable framework for the surface-sensitive morphological characterization of ultrathin 2D coatings and thin films. Full article
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16 pages, 2509 KB  
Article
Structural and Thermal Stability of TiN- and SiC-Based Multilayer Diffusion Barriers for Copper–Silicon Interfaces
by Symaiyl Keiinbay, Kair Kh. Nussupov, Assanali T. Sultanov, Ilya V. Zhirkov, Nurzhan B. Beisenkhanov and Alex A. Volinsky
Coatings 2026, 16(3), 276; https://doi.org/10.3390/coatings16030276 - 26 Feb 2026
Viewed by 903
Abstract
In this study, the diffusion barrier performance of TiN and SiC layers was investigated in Si/TiN/Cu, Si/TiN/SiC/Cu, and Si/SiC/TiN/Cu multilayer structures to address copper diffusion issues at silicon interfaces in microelectronics. Samples were annealed in argon at 500–800 °C for 30 min, and [...] Read more.
In this study, the diffusion barrier performance of TiN and SiC layers was investigated in Si/TiN/Cu, Si/TiN/SiC/Cu, and Si/SiC/TiN/Cu multilayer structures to address copper diffusion issues at silicon interfaces in microelectronics. Samples were annealed in argon at 500–800 °C for 30 min, and diffusion behavior was analyzed using X-ray diffraction (XRD) and sheet resistance measurements. The Cu3Si phase formed at 600 °C in the Si/TiN/Cu system, while no Cu3Si appeared in the Si/SiC/TiN/Cu system up to 700 °C, indicating improved stability. Complete copper diffusion occurred in all systems at 800 °C. Sheet resistance measurements corroborated the XRD findings, demonstrating that multilayer structures incorporating TiN and SiC significantly enhance thermal stability and suppress copper diffusion. Comparison of Si/SiC/TiN/Cu and Si/TiN/SiC/Cu stacks annealed at 700 °C revealed that the stability of TiN depends on layer sequence, with SiC effectively blocking Cu migration into TiN when placed adjacent to Cu. Structural and morphological properties of TiN films were also examined, confirming their suitability as diffusion barriers. Additionally, the feasibility of forming a low-resistivity TiSi2 layer through a single annealing step to create a TiSi2/TiN system was explored, highlighting potential applications in advanced device integration. Full article
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13 pages, 2511 KB  
Article
Enhancing the Mechanical Robustness of Aerosol-Based Brittle Pt/C Electrodes Through Thermal Annealing
by Nathan Heo, Won-Yong Jeong, Ji Hun Kim and Jae-Bum Pyo
Coatings 2025, 15(11), 1331; https://doi.org/10.3390/coatings15111331 - 15 Nov 2025
Viewed by 793
Abstract
Nanoporous Pt/C electrodes fabricated via aerosol coating offer excellent reactant delivery and electrochemical activity owing to their high porosity. However, the practical application prospects of such electrodes are limited by their poor mechanical properties. Herein, we quantitatively analyze the effects of thermal annealing [...] Read more.
Nanoporous Pt/C electrodes fabricated via aerosol coating offer excellent reactant delivery and electrochemical activity owing to their high porosity. However, the practical application prospects of such electrodes are limited by their poor mechanical properties. Herein, we quantitatively analyze the effects of thermal annealing (at 110, 150, 190, and 230 °C) on the mechanical stability and electrical properties of aerosol-based Pt/C electrodes. Post-annealing at an optimal temperature of 190 °C improved the tensile strength by 65.3%, increased their elongation from 0.82% to 1.78%, and decreased the electrical resistance while maintaining the secondary pore structure. Analyses of the electrode’s surface roughness, pore structure, and contact angle indicate that thermal reconstruction of the ionomer is crucial for stabilizing the electrode structure and controlling its surface properties. Finite element simulations using experimentally measured single-electrode properties enabled accurate prediction of the mechanical behavior of the membrane electrode assembly. These results provide design guidelines for balancing the process efficiency with the mechanical stability of aerosol-based Pt/C electrodes and can be used to improve their application prospects in aerosol-based fuel cell catalyst layers. Full article
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20 pages, 4461 KB  
Article
Mechanosynthesis of SbSI Targets for Pulsed Electron Deposition of Ferro-Photovoltaic Thin Films
by Michele Casappa, Elena Del Canale, Davide Delmonte, Francesco Pattini, Giulia Spaggiari, Anna Moliterni, Cinzia Giannini, Andrea Aroldi, Edgardo Ademar Saucedo Silva, Alejandro Navarro, Davide Calestani, Giovanna Trevisi, Marzio Rancan, Lidia Armelao, Matteo Bronzoni, Edmondo Gilioli and Stefano Rampino
Coatings 2025, 15(10), 1232; https://doi.org/10.3390/coatings15101232 - 21 Oct 2025
Viewed by 1019
Abstract
A solvent-free, solid-state mechanochemical method was developed to synthesize the chalcohalide compound SbSI at room temperature. Dry high-energy planetary ball milling of elemental antimony, sulfur, and iodine produced a pure, stoichiometric polycrystalline SbSI powder with an orthorhombic structure. This powder was then sintered [...] Read more.
A solvent-free, solid-state mechanochemical method was developed to synthesize the chalcohalide compound SbSI at room temperature. Dry high-energy planetary ball milling of elemental antimony, sulfur, and iodine produced a pure, stoichiometric polycrystalline SbSI powder with an orthorhombic structure. This powder was then sintered under mild thermal conditions to create dense targets. Amorphous SbSI thin films were subsequently deposited from these targets at room temperature using Pulsed Electron Deposition. The films maintained the correct stoichiometry and exhibited an optical bandgap of 1.89 eV. Post-deposition annealing at 90 °C in air successfully induced crystallization, demonstrating a viable, low-temperature, and eco-friendly route to produce polycrystalline SbSI thin films. This scalable approach has promising potential for optoelectronic and energy-harvesting applications. Full article
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10 pages, 1801 KB  
Article
Strong Radiative Cooling Coating Containing In Situ Grown TiO2/CNT Hybrids and Polyacrylic Acid Matrix
by Jiaziyi Wang, Yong Liu, Dapeng Liu, Yong Mu and Xilai Jia
Coatings 2025, 15(8), 921; https://doi.org/10.3390/coatings15080921 - 7 Aug 2025
Viewed by 1724
Abstract
Traditional forced-air cooling systems suffer from excessive energy consumption and noise pollution. This study proposes an innovative passive cooling strategy through developing aqueous radiative cooling coatings made from a combination of TiO2-decorated carbon nanotube (TiO2-CNT) hybrids and polyacrylic acid [...] Read more.
Traditional forced-air cooling systems suffer from excessive energy consumption and noise pollution. This study proposes an innovative passive cooling strategy through developing aqueous radiative cooling coatings made from a combination of TiO2-decorated carbon nanotube (TiO2-CNT) hybrids and polyacrylic acid (PAA), designed to simultaneously enhance the heat dissipation and improve the mechanical strength of the coating films. Based on CNTs’ exceptional thermal conductivity and record-high infrared emissivity, bead-like TiO2-CNT architectures have been prepared as the filler in PAA. The TiO2 nanoparticles were in situ grown on CNTs, forming a rough surface that can produce asperity contacts and enhance the strength of the TiO2-CNT/PAA composite. Moreover, this composite enhanced heat dissipation and achieved remarkable cooling efficiency at a small fraction of the filler (0.1 wt%). The optimized coating demonstrated a temperature reduction of 23.8 °C at an operation temperature of 180.7 °C, coupled with obvious mechanical reinforcement (tensile strength from 13.7 MPa of pure PAA to 17.1 MPa). This work achieves the combination of CNT and TiO2 nanoparticles for strong radiative cooling coating, important for energy-efficient thermal management. Full article
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15 pages, 1981 KB  
Article
Substrate-Dependent Characteristics of CuSbS2 Solar Absorber Layers Grown by Spray Pyrolysis
by Samaneh Shapouri, Elnaz Irani, Payam Rajabi Kalvani, Stefano Pasini, Gianluca Foti, Antonella Parisini and Alessio Bosio
Coatings 2025, 15(6), 683; https://doi.org/10.3390/coatings15060683 - 6 Jun 2025
Viewed by 1788
Abstract
Copper antimony sulfide (CuSbS2) is an affordable and eco-friendly solar absorber with an optimal bandgap and high absorption coefficient, and it stands out as a promising candidate for thin-film solar cells. This study investigates the effects of indium tin oxide (ITO), [...] Read more.
Copper antimony sulfide (CuSbS2) is an affordable and eco-friendly solar absorber with an optimal bandgap and high absorption coefficient, and it stands out as a promising candidate for thin-film solar cells. This study investigates the effects of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and glass substrates on the microstructural, morphological, and optical properties of CuSbS2 (CAS) layers synthesized via spray pyrolysis. X-ray Diffraction (XRD) and Raman spectroscopy analyses revealed that CAS phases formed on ITO and FTO substrates exhibited a phase composition without additional copper phases. However, the CAS layer on glass contained a copper sulfide (CuS) phase, which can be detrimental for solar cell applications. Furthermore, the influences of the substrate morphology and contact angle on the growth mechanisms of CAS layers was examined, highlighting the relationship between the substrate micromorphology and the resultant film characteristics. Advanced image processing techniques applied to Atomic Force Microscopy (AFM) images of the substrate surfaces facilitated a comprehensive comparison with the surface characteristics of the CAS films grown on those substrates. Field Emission Scanning Electron Microscopy (FESEM) indicated that CAS layers on ITO possessed larger grains than FTO, whereas those on FTO exhibited lower roughness with a more uniform grain distribution. Notably, the optical properties of the CAS layers correlated strongly with their microstructural and morphological characteristics. This work highlights the critical influence of substrate choice on the growth and characteristics of CAS layers through a comparative analysis. Full article
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10 pages, 2844 KB  
Article
Solvent Engineering and Molecular Doping Synergistically Boost CsPbIBr2 Solar Cell Efficiency
by Yani Lu, Jinping Ren and Jinke Kang
Coatings 2025, 15(4), 448; https://doi.org/10.3390/coatings15040448 - 10 Apr 2025
Cited by 1 | Viewed by 1213
Abstract
Perovskite solar cells have garnered significant attention due to their outstanding optoelectronic properties, ease of fabrication, and cost-effectiveness, making them a promising candidate for next-generation photovoltaic technologies. However, CsPbIBr2-based perovskites currently face critical challenges regarding their limited efficiency and relatively poor [...] Read more.
Perovskite solar cells have garnered significant attention due to their outstanding optoelectronic properties, ease of fabrication, and cost-effectiveness, making them a promising candidate for next-generation photovoltaic technologies. However, CsPbIBr2-based perovskites currently face critical challenges regarding their limited efficiency and relatively poor long-term stability, hindering their broader commercial applications. In this study, we systematically investigated the morphological effects induced by different solvents, including dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO), on the formation and characteristics of lead bromide (PbBr2) complexes. Further optimization was achieved through the innovative incorporation of trimesoyl chloride (TMC) doping into the perovskite precursor solution. The optimized precursor solution was subsequently processed using a spin-coating and annealing method, resulting in high-quality CsPbIBr2 perovskite thin films with improved morphological and optoelectronic properties. The experimental results demonstrated a remarkable enhancement in power conversion efficiency (PCE), with an increase from an initial value of 6.2% up to 10.2%. Furthermore, the optimized CsPbIBr2 solar cells exhibited excellent stability, maintaining over 80% of their initial efficiency after continuous aging for 250 h in ambient air conditions. This study presents an effective strategy for the controlled morphological and compositional engineering of wide-bandgap perovskite materials, providing a significant step forward in the advancement of perovskite photovoltaic technology. Full article
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12 pages, 2359 KB  
Article
Polyacetylene Prepared by Chemical Dehydration of Poly(Vinyl Alcohol)
by Gianfranco Carotenuto and Luigi Nicolais
Coatings 2024, 14(9), 1216; https://doi.org/10.3390/coatings14091216 - 20 Sep 2024
Cited by 1 | Viewed by 3273
Abstract
Recently, polyacetylene (PA) has been receiving renewed scientific attention due to its electrical properties, potentially useful for energy applications (e.g., fabrication of electrodes for rechargeable batteries and supercapacitors), and unique functional characteristics (e.g., gas trap, oxygen scavenger, EMI shielding, etc.). This chemical compound [...] Read more.
Recently, polyacetylene (PA) has been receiving renewed scientific attention due to its electrical properties, potentially useful for energy applications (e.g., fabrication of electrodes for rechargeable batteries and supercapacitors), and unique functional characteristics (e.g., gas trap, oxygen scavenger, EMI shielding, etc.). This chemical compound can be obtained in the form of polyacetylene–PVOH copolymers simply through the chemical dehydration of poly(vinyl alcohol) (PVOH), which is a very common type of polymer, widely used in packaging and other technological areas. This very inexpensive chemical reaction for the large-scale synthesis of PA/polyvinylenes is investigated by reacting PVOH with sulfuric acid at room temperature. In this process, PVOH, shaped in the form of a film, is dipped in sulfuric acid (i.e., H2SO4 at 95%–97%) and, after complete chemical dehydration, it is mechanically removed from the liquid phase by using a nylon sieve. The reduction process leads to a substantial PVOH film conversion into PA, as demonstrated by infrared spectroscopy (ATR mode). Indeed, the ATR spectrum of the reaction product includes all the characteristic absorption bands of PA. The reaction product is also characterized through the use of UV–Vis spectroscopy in order to evidence the presence in the structure of conjugated carbon–carbon double bonds of various lengths. Differential scanning calorimetry (DSC) and thermogravimetric analysis are used to investigate the PA solid-state cis–trans isomerization and thermal stability in air and nitrogen, respectively. XRD is used to verify the polymer amorphous nature. Full article
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