Research Groups

RESEARCH UNIT: Functional Surfaces and Interfaces

Physical Chemistry of Surfaces and Interfaces (SURFACES)

We have contributed to unveil: i) the critical role that the structure and properties of surfaces and interfaces play on processes as diverse as graphene and organic thin film growth or water dissociation and ice nucleation; ii) the underlying reason for the changes of the open circuit voltage in mixed cation perovskite solar cells.

Our research focus on understanding the physical and chemical processes taking place at surfaces by designing experimental strategies correlating the nanoscale properties of nanostructures, surfaces and interfaces. We employ Scanning Probe Microscopes (SPM) to gain insight at the nanoscale into mechanical, tribological and electronic/electrical properties (AFM, FFM, STM, C-AFM, KPFM) as well as X-ray diffraction and photoelectron spectroscopies using synchrotron facilities. Part of the group is involved in developing multifrequency dynamic AFM modes.

Our main effort is devoted to organic semiconductors with relevance as active layers for electronic devices but also to the characterization and manipulation of nanoscale properties of interfaces including 2D materials (graphene), functional oxides (ferroelectrics), ceramics (carbides) and hybrid materials (perovskites) for energy applications.

Our investigation spans from fundamental issues in organic growth and small molecules self-assembling to the electronic response of metal-organic junctions during operation of devices, resistive switching mechanisms or the interaction of water with ferroelectric surfaces and its role in surface charge screening.

Members

  • Dr. Esther Barrena - Tenured Scientist
  • Prof. Carmen Ocal - Research Professor
  • Dr. Albert Verdaguer - Tenured Scientist
  • Dr. Elzbieta Pach - Postdoctoral Researcher
  • Percy Rogger Palacios - PhD Researcher
  • Adara Babuji - PhD Researcher
  • Francesco Silvestri - PhD Researcher
Energy level in perovskite solar cells extracted from KPFM at surfaces of pristine CsFAMAPbIBr and diverse HTM devices; E-SEM reveals that microsized pores at the feldspars surface dominate ice nucleation. Graphene growth on polycrystalline SiC. Highly ordered packing of C60 on Cu(111) by STM in UHV

Achievements

Among the research achievements of the group, we select some examples from different fields.

Solar cells: Outstandingly, CsFAMAPbIBr based devices using hole transport materials (HTMs), with close chemical and physical properties, provide different device performances. Unexpectedly, in addition of HTM influence in recombination, we have found that each HTM provokes an important change in the energy level position with impact on the device VOC. Collaboration with ICIQ-IMDEA-UCM-URV.

2D materials: Due to the inherent random orientation of grains in a polycrystal, epitaxial graphene (EG) grown by Spark Plasma Sintering (SPS) on dense polycrystalline SiC is a benchmark for surface properties tests. We have demonstrated that the quality of the fabricated EG films makes the 2D material attractive for applications and SPS technique itself is a reliable methodology for preparing EG on SiC components with real possibilities for scaling-up at low cost. Collaboration with ICV.

Molecules on surfaces:  We study fundamental aspects of the molecule-metal interface and the generation of novel nanostructures using self-assembly of molecules (C60, ClAlPc, FAlPc, C8-BTBT, C60F48…) on single crystals (Au, Ni, Ir, Cu..). Through an understanding of the complex interplay between structural features, intermolecular and molecule-substrate interactions, we have opened new research in 2D molecular assemblies and chemical reactivity at the single molecule level. Research developed in our STM in UHV located in ALBA, through agreement since 2011.

Environment: Feldspars, considered the most important ice nucleation agent present in the atmosphere, induce ice nucleation mainly inside micro to nano size pores present on its surface. The studies of the group on ice nucleation using feldspars have allowed a patent co-owned by CSIC published in 2019.

Publications

Energy Alignment and Recombination in Perovskite Solar Cells: Weighted Influence on the Open Circuit Voltage
I. Gelmettia, N.F. Montcada, A. Pérez-Rodríguez, E. Barrena, C. Ocal, I. García-Benito, A. Molina-Ontoria, N. Martín, A. Vidal-Ferrana, E. Palomares
Energy and Environment Science 12, 1309-1316, 2019

Bipolar resistive switching on TiO2/Au by conducting Atomic Force Microscopy
M. Linares Moreau, M. Barella, L. López-Mir, N. Ghenzi, F. Golmar, L.P. Granja, C. Ocal, P. Levy
Materials Today: Proceedings 14, 100–103, 2019

Water adsorption, dissociation and oxidation on SrTiO3 and ferroelectric surfaces revealed by ambient pressure X-ray photoelectron spectroscopy
Phys. Chem. Chem. Phys. 21, 4920-4930, 2019

Effect of the Molecular Polarizability of SAMs on the Work Function Modification of Gold: Closed- versus Open-Shell Donor–Acceptor SAMs
V. Diez-Cabanes, D. C. Morales, M. Souto, M. Paradinas, F. Delchiaro, A. Painelli, C. Ocal, D. Cornil, J. Cornil, J. Veciana, I. Ratera
Adv. Mater. Technol. 4, 1800152, 2019

Face dependent footprints of carpet-like graphene films grown on polycrystalline silicon carbide
C. Ramírez, E. García, E. Barrena, A. De Pablos, M. Belmonte, M.I. Osendi, P. Miranzo, C. Ocal
Carbon 153, 417-427, 2019

Pores Dominate Ice Nucleation on Feldspars
E. Pach, A. Verdaguer.
Journal of Physical Chemistry C 123, 34, 20998–21004, 2019

Surface charged species and electrochemistry of ferroelectric thin film
N. Domingo, I. Gaponenko, K. Cordero-Edwards, N. Stucki, V. Pérez-Dieste, C. Escudero, E. Pach, A. Verdaguer, P. Paruch
Nanoscale, 11, 17920, 2019

PATENTS

Prodèdé de Fabrication de Niege Artificielle Produit pour la Mise en Uvre du Procèdé
EU- 19305203.2 Publication date: 28/08/2019. The use of micron size feldspar powder as a natural ice-nucleation agent to use in snowmaking has been patented. The patent covers the use of such materials by adding them to the water that is going to be use to make snow and diffrent preparation methods of the feldspar surface to activate it as a good ice nucleation agent. Inventors: A. Verdaguer and M. Galvin. Ownership: CSIC and Technoalpin (France).

Coordination
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