Jorge A. Budagosky and Alberto García-Cristobal
Nanomaterials 2022,14 (17), 3052
A three-dimensional kinetic Monte Carlo methodology is developed to study the strained epitaxial growth of wurtzite GaN/AlN quantum dots. It describes the kinetics of effective GaN adatoms on an hexagonal lattice. The elastic strain energy is evaluated by a purposely devised procedure: first, we take advantage of the fact that the deformation in a lattice-mismatched heterostructure is equivalent to that obtained by assuming that one of the regions of the system is subjected to a properly chosen uniform stress (Eshelby inclusion concept), and then the strain is obtained by applying the Green’s function method. The standard Monte Carlo method has been modified to implement a multiscale algorithm that allows the isolated adatoms to perform long diffusion jumps. With these state-of-the art modifications, it is possible to perform efficiently simulations over large areas and long elapsed times. We have taylored the model to the conditions of molecular beam epitaxy under N-rich conditions. The corresponding simulations reproduce the different stages of the Stranski–Krastanov transition, showing quantitative agreement with the experimental findings concerning the critical deposition, and island size and density. The influence of growth parameters, such as the relative fluxes of Ga and N and the substrate temperature, is also studied and found to be consistent with the experimental observations. In addition, the growth of stacked layers of quantum dots is also simulated and the conditions for their vertical alignment and homogenization are illustrated. In summary, the developed methodology allows one to reproduce the main features of the self-organized quantum dot growth and to understand the microscopic mechanisms at play.
Rhodamine 6G and 800 intermolecular heteroaggregates embedded in PMMA for near-infrared wavelength shifting
Javier Castillo-Seoane, Lola González-García, Jose Manuel Obrero-Pérez, Francisco Javier Aparicio, Ana Isabel Borrás, Agustín R. González Elipe, Ángel Barranco y Juan Ramon Sanchez-Valencia
Journal of Materials Chemistry C, 2022, 10, 7119-7131
The opto-electronic properties of small-molecules and functional dyes usually differ when incorporated into solid matrices with respect to their isolated form due to an aggregation phenomenon that alters their optical and fluorescent properties. These spectroscopic modifications are studied in the framework of the exciton theory of aggregates, which has been extensively applied in the literature for the study of molecular aggregates of the same type of molecules (homoaggregation). Despite the demonstrated potential of the control of the heteroaggregation process (aggregation of different types of molecules), most of the reported works are devoted to intramolecular aggregates, complex molecules formed by several chromophores attached by organic linkers. The intramolecular aggregates are specifically designed to hold a certain molecular structure that, on the basis of the exciton theory, modifies their optical and fluorescent properties with respect to the isolated chromophores that form the molecule. The present article describes in detail the incorporation of Rhodamine 6G (Rh6G) and 800 (Rh800) into polymeric matrices of poly-(methyl methacrylate), PMMA. The simultaneous incorporation of both dyes results in an enhanced fluorescent emission in the near-infrared (NIR), originating from the formation of ground-state Rh6G–Rh800 intermolecular heteroaggregates. The systematic control of the concentration of both rhodamines provides a model system for the elucidation of the heteroaggregate formation. The efficient energy transfer between Rh6G and Rh800 molecules can be used as wavelength shifters to convert effectively the light from visible to NIR, a very convenient wavelength range for many practical applications which make use of inexpensive commercial detectors and systems.
Ultrathin Plasma Polymer Passivation of Perovskite Solar Cells for Improved Stability and Reproducibility
Jose Manuel Obrero-Perez, Lidia Contreras-Bernal, Fernando Nuñez-Galvez, Javier Castillo-Seoane, Karen Valadez-Villalobos, Francisco Javier Aparicio, Juan A. Anta, Ana Borrás, Juan Ramon Sanchez-Valencia, Ángel Barranco
Advanced Energy Materials 2022 (12), 2200812
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 techniques reported to date to tackle such issues recurrently involve the use of solvent methods that would further complicate their transfer to industry. Herein a reliable alternative relaying in the implementation of an ultrathin plasma polymer as a passivation interface between the electron transport layer and the hybrid perovskite layer is presented. Such a nanoengineered interface provides solar devices with increased long-term stability under ambient conditions. Thus, without involving 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, with a champion efficiency of 19.2%, a remarkable value for Li-free standard mesoporous n-i-p architectures, as well as significantly improved reproducibility.
Javier Castillo-Seoane, Lidia Contreras-Bernal, Jose Manuel Obrero-Perez, Xabier García-Casas, Francisco Lorenzo-Lázaro, Francisco Javier Aparicio, Carmen Lopez-Santos, Teresa Cristina Rojas, Juan Antonio Anta, Ana Borrás, Ángel Barranco, Juan Ramon Sanchez-Valencia
Advanced Materials 2022 (18), 2107739
Polarizers are ubiquitous components in current optoelectronic devices as displays or photographic cameras. Yet, control over light polarization is an unsolved challenge, since the main drawback of the existing display technologies is the significant optical losses. In such a context, organometal halide perovskites (OMHP) can play a decisive role given their flexible synthesis with tunable optical properties such as bandgap and photoluminescence, and excellent light emission with a low non-radiative recombination rate. Therefore, along with their outstanding electrical properties have elevated hybrid perovskites as the material of choice in photovoltaics and optoelectronics. Among the different OMHP nanostructures, nanowires and nanorods have lately arisen as key players in the control of light polarization for lighting or detector applications. Herein, the fabrication of highly aligned and anisotropic methylammonium lead iodide perovskite nanowalls by glancing-angle deposition, which is compatible with most substrates, is presented. Their high alignment degree provides the samples with anisotropic optical properties such as light absorption and photoluminescence. Furthermore, their implementation in photovoltaic devices provides them with a polarization-sensitive response. This facile vacuum-based approach embodies a milestone in the development of last-generation polarization-sensitive perovskite-based optoelectronic devices such as lighting appliances or self-powered photodetectors.
Coarse-grained approach to amorphous and anisotropic materials in kinetic Monte Carlo thin-film growth simulations: A case study of TiO2 and ZnO by plasma-enhanced chemical vapor deposition
Jorge Budagosky, Xabier García-Casas, Juan R. Sánchez-Valencia, Ángel Barranco, Ana Borrás
Plasma Processes and Polymers 19 (2022) 2270008
The growth of TiO2and ZnO thin films is studied by means of coarse-grained kinetic Monte Carlo simulations under conditions typically encountered in plasma-enhanced chemical vapor deposition experiments. The basis of our approach is known to work well to simulate the growth of amorphous materials using cubic grids and is extended here to reproduce not only the morphological characteristics and scaling properties of amorphous TiO2 but also the growth of polycrystalline ZnO with a good approximation, including the evolution of the film texture during growth and its dependence on experimental conditions. The results of the simulations have been compared with available experimental data obtained by X-ray diffraction, analysis of the texture coefficients, atomic force microscopy, and scanning electron microscopy.
Plasma engineering of microstructured piezo – Triboelectric hybrid nanogenerators for wide bandwidth vibration energy harvesting
Xabier García-Casas, Ali Ghaffarinejad, Francisco J.Aparicio, Javier Castillo-Seoane, Carmen López-Santos, Juan P. Espinós, José Cotrino, Juan Ramón Sánchez-Valencia, ÁngelBarranco and Ana Borrás
Nano Energy 91 (2022), 106673
We introduce herein the advanced application of low-pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma-assisted assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of polydimethylsiloxane (PDMS) provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact–separation triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz.
One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR
Javier Castillo-Seoane, Jorge Gil-Rostra, Víctor López-Flores, Gabriel Lozano, F. Javier Ferrer, Juan P. Espinós, Kostya (Ken) Ostrikov, Francisco Yubero, Agustín R. González-Elipe, Ángel Barranco, Juan R. Sánchez-Valencia and Ana Isabel Borrás
Nanoscale,13 (32), 13882-13895
The eventual exploitation of one-dimensional nanomaterials needs the development of scalable, high yield, homogeneous and environmentally friendly methods capable of meeting the requirements for fabrication of functional nanomaterials with properties on demand. In this article, we demonstrate a vacuum and plasma one-reactor approach for the synthesis of fundamental common elements in solar energy and optoelectronics, i.e. the transparent conducting electrode but in the form of nanotube and nanotree architectures. Although the process is generic and can be used for a variety of TCOs and wide-bandgap semiconductors, we focus herein on indium doped tin oxide (ITO) as the most previously researched in previous applications. This protocol combines widely applied deposition techniques such as thermal evaporation for the formation of organic nanowires serving as 1D and 3D soft templates, deposition of polycrystalline layers by magnetron sputtering, and removal of the templates by simply annealing under mild vacuum conditions. The process variables are tuned to control the stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees. Four-probe characterization reveals the improved lateral connectivity of the ITO nanotrees and applied on individual nanotubes shows resistivities as low as 3.5 ± 0.9 × 10–4 Ω cm, a value comparable to that of single-crystalline counterparts. The assessment of diffuse reflectance and transmittance in the UV-Vis range confirms the viability of the supported ITO nanotubes as random optical media working as strong scattering layers. Their further ability to form ITO nanotrees opens a path for practical applications as ultra-broadband absorbers in the NIR. The demonstrated low resistivity and optical properties of these ITO nanostructures open a way for their use in LEDs, IR shields, energy harvesting, nanosensors, and photoelectrochemical applications.
Plasma-Assisted Deposition of TiO2 3D Nanomembranes: Selective Wetting, Superomniphobicity, and Self-Cleaning
Laura Montes, Jose M. Román, Xabier García-Casas, Javier Castillo-Seoane, Juan Ramon Sanchez-Valencia, Ángel Barranco, Carmen López-Santos and Ana Borrás
Advanced Materials Interface8 (21), 2100767
Fabrication of tunable wetting surfaces is sought for the last years given its importance on energy, biomaterials and antimicrobials, water purification, microfluidics, and smart surfaces. Liquid management on surfaces mainly depends on the control at the micro- and nanoscale of both roughness and chemical composition. Herein, the combination of a soft-template method and plasma-enhanced chemical vapor deposition is presented for the synthesis of TiO2 nanofibers on porous substrates such as cellulose and stainless-steel membranes. The protocol, carried out under mild conditions, produces 3D nanomembranes with superhydrophobicity and oleophilicity that are tested as microliter water/oil filters. Photoactivation of TiO2 by UV illumination provides a straightforward approach for wetting tunability that converts the surface into amphiphilic. A final chemical modification of the TiO2 nanofibers by embedding them in an elastomeric polymeric shell and by fluorine-based grafting opens the path toward the formation of superomniphobic and self-cleaning surfaces with long-lasting lifetimes. Thus, a reliable procedure is demonstrated for the fabrication of TiO2 nanofibers, which allows the modification of porous supports and provides an innovative route for the development of 3D nanomembranes with under design wetting. This protocol is extendable to alternative metal oxides, metals, and core@shell nanoarchitectures with potential multifunctionalities.
Nicolas Filippin, Javier Castillo-Seoane, M. Carmen López-Santos, Cristina T. Rojas, Kostya Ostrikov, Angel Barranco, Juan R. Sánchez-Valencia, and Ana Borrás
ACS Applied Materials & Interfaces 2020 12 (45), 50721-50733
Supported porous nanostructures developed by plasma processing of metal phthalocyanines and porphyrins
Obrero, J.M., Filippin, A.N., Alcaire, M., Sanchez-Valencia, J.R. , Jacob, M., Matei, C., Aparicio, F.J., Macias-Montero, M., Rojas, T.C., Espinos, J.P., Saghi, Z., Barranco, A., Borras, A.
Frontiers in Chemistry Accepted
Enhanced Stability of Perovskite Solar Cells Incorporating Dopant-Free Crystalline Spiro-OMeTAD Layers by Vacuum Sublimation
Barranco, A., Lopez-Santos, M.C., Idigoras, J., Aparicio, F.J., Obrero-Perez, J., Lopez-Flores, V., Contreras-Bernal, L., Rico, V., Ferrer, J., Espinos, J.P., Borras, A., Anta, J.A., Sanchez-Valencia, J.R.
Advanced Energy Materials, 10 (2020) 1901524
3D Organic Nanofabrics: Plasma-Assisted Synthesis and Antifreezing Behavior of Superhydrophobic and Lubricant-Infused Slippery Surfaces
Alcaire, M., Lopez-Santos, C., Aparicio, F.J., Sanchez-Valencia, J.R., Obrero, J.M., Saghi, Z., Rico, V.J., De La Fuente, G., Gonzalez-Elipe, A.R., Barranco, A., Borras, A.
Langmuir, 35 (2019) 16876-16885
Rico, V.J., López-Santos, C., Villagrá, M., Espinós, J.P., De La Fuente, G.F., Angurel, L.A., Borrás, A., González-Elipe, A.R.
Langmuir, 35 (2019) 6483-6491
Przybyszewski, B., Boczkowska, A., Kozera, R., Mora, J., Garcia, P., Aguero, A., Borras, A.
Coatings, 9 (2019) 811
Filippin, A.N., Sanchez-Valencia, J.R., Garcia-Casas, X., Lopez-Flores, V., Macias-Montero, M., Frutos, F., Barranco, A., Borras, A.
Nano Energy, 58 (2019) 476-483
Mora-Boza, A., Aparicio, F.J., Alcaire, M., López-Santos, C., Espinós, J.P., Torres-Lagares, D., Borrás, A., Barranco, A.
Frontiers of Chemical Science and Engineering, 13 (2019) 330-339
Plasma Enabled Conformal and Damage Free Encapsulation of Fragile Molecular Matter: from Surface-Supported to On-Device Nanostructures
Alcaire, M., Aparicio, F.J., Obrero, J., López-Santos, C., Garcia-Garcia, F.J., Sánchez-Valencia, J.R., Frutos, F., Ostrikov, K., Borrás, A., Barranco, A.
Advanced Functional Materials, 29 (2019) 1903535
Enhancing Moisture and Water Resistance in Perovskite Solar Cells by Encapsulation with Ultrathin Plasma Polymers
Idígoras, J., Aparicio, F.J., Contreras-Bernal, L., Ramos-Terrón, S., Alcaire, M., Sánchez-Valencia, J.R., Borras, A., Barranco, Á., Anta, J.A.
ACS Applied Materials and Interfaces, 10 (2018) 11587-11594
The Role of Surface Recombination on the Performance of Perovskite Solar Cells: Effect of Morphology and Crystalline Phase of TiO2 Contact
Idígoras, J., Contreras-Bernal, L., Cave, J.M., Courtier, N.E., Barranco, A., Borras, A., Sánchez-Valencia, J.R., Anta, J.A., Walker, A.B.
Advanced Materials Interfaces, 5 (2018) 1801076