arXiv subjects

Fernando Nunez-Galvez

Publications and source records attributed to Fernando Nunez-Galvez.

6 recordsLinked to original sources

arXiv2026

Adamantane plasma polymers: fluorine-free vacuum-processable triboelectric thin films for all-triboelectric nanogenerator configurations

Triboelectric nanogenerators (TENGs) are major drivers in on-site power generation for smart devices, enable self-powered sensors, and introduce novel catalytic processes. Here, we present the advantages of adamantane plasma layers as bivalently triboelectric surfaces capable of exhibiting both tribopositive and tribonegative character through simple modification of the synthesis conditions without the need for additives or functionalization. Fabrication facing or backfacing the plasma yields thin film polymers with different dielectric constants, Young's moduli, and secondary electron emission. The conformality, stability, and processability of the polymers enable direct implementation across solid-solid, solid-liquid, and hybrid piezo-triboelectric configurations. Additional texturization by buckling is shown to provide voltage and current outputs as high as 90 V cm2 and 0.6 uA for a 2.8 um (tribonegative) vs. 400 nm (tribopositive) combination. A maximum power density of 2.1 uW cm-2 is generated from salty droplets in a switch-electrode drop-TENG configuration employing a 500 nm-thick tribopositive adamantane polymer as the triboelectric surface. These layers have demonstrated outstanding durability, enabling more than 10^5 cycles in solid-solid nanogenerators and 10^4 droplet impacts in solid-liquid configurations. The synthetic method is environmentally friendly and industrially scalable, making the adamantane plasma polymer a reliable and competitive solution for thin film triboelectric materials.

cond-mat.mtrl-sci↗

arXiv2026

Water-resistant hybrid perovskite solar cell -- drop triboelectric energy harvester

Hybrid energy-harvesting systems combining perovskite solar cells (PSCs) with drop-driven triboelectric nanogenerators (D-TENGs) provide continuous power under various weather conditions. However, halide perovskites' vulnerability to moisture hampers widespread use. We present plasma-deposited fluorinated polymers (CFX) as multifunctional encapsulation layers offering water resistance, triboelectric functionality, and > 90 % optical transparency. These conformal, room-temperature, solvent-free coatings protect PSCs without reducing performance; encapsulated cells maintained a PCE of 17.9 %, and devices kept over 50 % of initial PCE after 10 days in high humidity and temperature. CFx layers also enabled compatibility with UV-curable resins, creating a hybrid PSC/D-TENG capable of harvesting solar and rain energy. This device retained 80 % of its performance after 300 hours of humid operation and stayed stable under continuous dripping and illumination for over 5 hours. Optimizing CFx's chemical composition improved triboelectric performance. Using the same CFx layer for encapsulation and triboelectric function, the device achieved 11.6 mA/cm2 short-circuit current under 0.5 sun and 12 V peak voltage per raindrop, enabling simultaneous solar and rain energy harvesting. A self-charging prototype powered LED arrays via a boost converter, demonstrating practical multisource energy harvesting.

cond-mat.mtrl-sci↗

arXiv2025

Enhanced Luminous Transmission and Solar Modulation in Thermochromic VO2 Aerogel-Like Films via Remote Plasma Deposition

Vanadium dioxide (VO2) is a thermochromic material that undergoes a phase transition from a monoclinic semiconducting state to a rutile metallic state at 68 degrees C, a temperature close to room temperature. This property makes VO2 particularly valuable in applications such as optical and electrical switches, data storage, neuromorphic computing, and remarkably dynamic smart windows for solar radiation control. VO2 typically needs to be synthesized for these applications as nanostructured thin films. Over the past few decades, significant efforts have been made to control the thermochromic properties of VO2 through crystal structure tuning, doping, and the development of VO2 nanocomposites. Additionally, introducing nano- and mesoporosity has been shown to enhance the optical properties of thermochromic VO2 films. This study presents a methodology for producing highly porous, aerogel-like V2O5 films, which can be thermally processed to form aerogel-like VO2 films. This process is based on sequential plasma polymerization and plasma etching to produce aerogel-like V2O5 films that are annealed to yield ultraporous nanocrystalline VO2 films. The sacrificial vanadium-containing plasma polymers are obtained by remote plasma-assisted vacuum deposition (RPAVD) using vanadyl porphyrin as a precursor and Ar as plasma gas. The aerogel-like VO2 films show exceptional thermochromic performance with luminous transmittances higher than 54%, solar modulation up to 18.8%, and IR modulation up to 35.5%. The presented plasma methodology is versatile, allowing both the synthesis of VO2 plasmonic structures to enhance the thermochromic response and the encapsulation of films to improve their stability in air dramatically. Additionally, this solvent-free synthetic method is fully compatible with doping procedures, scalable, and holds great potential for designing and optimizing smart window coatings.

physics.app-ph↗

arXiv2025

Low-Temperature Remote Plasma Synthesis of Highly Porous TiO$_2$ as Electron Transport Layers in Perovskite Solar Cells

Halide perovskite solar cells (PSCs) offer high efficiency and low costs, making them key for future photovoltaics. Optimizing charge transport layers is crucial, with porous TiO$_2$ widely used as electron transport layers (ETL) due to its energy alignment, transparency, and abundance. However, its efficiency relies on crystallinity requiring high-temperature processing (>450$^\circ$C), increasing costs and limiting flexible substrates. Low-temperature wet-chemical methods face scalability issues due to material waste and hazardous solvents. In this context, plasma-based technologies are emerging as a more efficient and sustainable alternative to oxide-based ETLs. This study presents the synthesis of TiO$_2$ layers using an advanced plasma method combining remote plasma-assisted vacuum deposition (RPAVD) and soft plasma etching (SPE) at mild temperatures (<200$^\circ$C), allowing control of microstructure and porosity. The resulting nanocolumnar film, decorated with a highly porous aerogel-like layer, enhances optical and electronic properties. These plasma-synthesized TiO$_2$ layers are antireflective and improve the efficiency in porous n-i-p PSCs, matching the performance of high-temperature reference cells. These PSCs achieve a champion PCE of 14.6%, a high value compared to reference devices synthesized at 450°C. Impedance spectroscopy confirms high recombination resistance and stable capacitance, linked to improved perovskite crystallinity. Our results highlight the potential of the RPAVD+SPE approach for producing low-temperature efficient ETLs, providing a feasible, industrially scalable, and eco-friendly alternative for manufacturing flexible, high-performance photovoltaic devices.

cond-mat.mtrl-sci↗

arXiv2024

Triboelectric Pixels as building blocks for microscale and large area integration of drop energy harvesters

The ultimate step towards the exploitation of water as a clean and renewable energy source addresses the energies stored in the low frequencies of liquid flows, which demands flexible solutions to adapt to multiple scenarios, from raindrops to waves, including water moving in pipelines and microdevices. Thus, harvesting low-frequency flows is a young concept compared to solar and wind powers, where triboelectric nanogenerators have been revealed as the most promising relevant actors. However, despite widespread attempts by researchers, the drop energy harvesters' output power is still low, mainly because of the limitations in candidates endowed with ideal triboelectric and wetting properties and also the non-optimal and centimetre-scale device architecture that prevents the conversion of the complete kinetic energy of impinging drops. Herein, we disclose a microscale triboelectric nanogenerator that can harvest a high density of electrical power from drops through a single, submillisecond, long-lasting step. The mechanism relies on an instantaneous electrical capacitance variation owing to the high-speed contact of the drops with the electrodes' active area. We discuss the role of the precharged effect of the triboelectric surface in the time characteristic of the conversion event. The capacitive and microscale structure of the device is endowed with a small form factor that allows for the production of densely packed arrays. The proposed architecture can be adjusted to different liquids and scales and is compatible with a variety of triboelectric surfaces, including flexible, transparent, and thin-film approaches.

physics.app-ph↗

arXiv2022

Ultrathin plasma polymer passivation of perovskite solar cells for improved stability and reproducibility

Despite the youthfulness of hybrid halide perovskite solar cells, their efficiencies are currently comparable to commercial silicon and have surpassed quantum-dots solar cells. Yet, the scalability of these devices is a challenge due to their low reproducibility and stability under environmental conditions. However, the methods reported to date to tackle such issues recurrently involve the use of solvent methods that would further complicate their transfer to industry. Herein we present a reliable alternative relaying in the implementation of an ultrathin plasma polymer as passivation interface between the electron transport material and the hybrid perovskite layer. Such nanoengineering interface provides solar devices with increased long-term stability under ambient conditions. Thus, without consideringr any additional encapsulation step, the cells retain more than 80 % of their efficiency after being exposed to the ambient atmosphere for more than 1000 h. Moreover, this plasma polymer passivation strategy significantly improves the coverage of the mesoporous scaffold by the perovskite layer, providing the solar cells with enhanced performance as well as improved reproducibility.

cond-mat.mtrl-sci↗