Research Groups

RESEARCH UNIT: Functional Surfaces and Interfaces

Physical Chemistry of Surfaces and Interfaces (SURFACES)

The group has contributed to the advance of interface engineering through control of the organic semiconductor growth and the use of dopants. By exploring and understanding the processes occurring at the surface of diverse organic-organic and organic-metal systems, we revealed the implications of structural details in device stability and performance.

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

Successful strategies enhancing the stability of organic semiconductor devices. Interface and thin film engineering via blending with specific polymers, designing the molecular side groups or inducing selective doping. Real space visualization of the metal specific de-halogenation of the strong acceptors fluorinated fullerenes C60F48.

Achievements

In the frame of our well stablished lines, the group research has focused on surface engineering, through thin film growth, to modify and improve the materials’ properties via correlation of the surface nanoscale characteristics with macroscale responses. We employ diverse modes of Scanning Probe Microscopes (SPM) and combine this approach with in-situ operando measurements of thin film devices, such as organic field effect transistors. To get insight on the structural order and electronic characteristics of different organic materials we have also performed X-ray diffraction and photoelectron spectroscopies in synchrotron facilities.

In the last period, we have devoted special attention to the influence of the particular structure of the organic semiconductor (OSC) molecules themselves on the structural and morphological details of the interfaces formed during growth. Moreover, we have studied the consequences of incorporating small molecules as dopants and demonstrated why blending OSCs with insulating polymers can enhance device stability by trapping surface-induced polymorphs.

Remarkably, we have elucidated the influence of the substitutional side groups of the OSC on the properties of the interface created when it is in contact with dopants, as well as the beneficial role of some small molecules as selective dopants and structural stabilizers. On the other hand, because the importance of the interfaces between the organic material and metallic electrodes in devices, we started a new research line investigating on-surface processes and reactions taking place when small molecules approach a metal surface.

Outstandingly, we have experimentally observed, and theoretically corroborated, the strong dependence on the type of metal for the on surface de-fluorination of strong acceptors as fluorinated fullerenes.

Publications

Impact of Nanomorphology on Surface Doping of Organic Semiconductors: The Pentacene−C60F48 Interface
F. Silvestri, M.J. Prieto, A. Babuji, L.C. Tănase, L. de Souza Caldas, O. Solomeshch, Th. Schmidt, C. Ocal, E. Barrena
ACS Appl. Mater. Interfaces 2020, 12, 22, 25444–25452, 10.1021/acsami.0c05583

Double Beneficial Role of Fluorinated Fullerene Dopants on Organic Thin Film Transistors: Structural Stability and Improved Performance
A. Babuji, I. Temiño, A. Pérez-Rodríguez, O. Solomeshch, N. Tessler, M. Vila, J. Li, M. Mas-Torrent, C. Ocal, E. Barrena
ACS Appl. Mater. Interfaces 2020, 12, 25, 28416–28425, 10.1021/acsami.0c06418

Surface specificity and mechanistic pathway of de-fluorination of C60F48 on coinage metals
R. Palacios-Rivera, D. C. Malaspina, N. Tessler, O. Solomeshch, J. Faraudo, E. Barrena, C. Ocal
Nanoscale Advances 2020, 2, 4529-4538, 10.1039/D0NA00513D

Enhancing long-term device stability using thin film blends of small molecule semiconductors and insulating polymers to trap surface-induced polymorphs
T. Salzillo, A. Campos, A. Babuji, R. Santiago, S.T. Bromley, C. Ocal, E. Barrena, R. Jouclas, C. Ruzie, G. Schweicher, Y. H. Geerts, M. Mas-Torrent
Adv. Funct. Mater. 2020, 2006115, 10.1002.admf.202006115

Effect of the Organic Semiconductor Side Groups on the Structural and Electronic Properties of Their Interface with Dopants
A. Babuji, F. Silvestri, L. Pithan, A. Richard, Y. H. Geerts, N. Tessler, O. Solomeshch, C. Ocal, E. Barrena
ACS Appl. Mater. Interfaces 2020, 12, 51, 57578–57586 10.1021/acsami.0c172713

Main projects

Spins for efficient photovoltaic devices based on organic molecules
European Union’s Horizon 2020 Research and Innovation Program under grant Agreement No. 730872 and the Marie Skłodowska-Curie Grant Agreement No. 722651
Esther Barrena
2017 - 2020

Scan-based strategies for engineering ordered nanoscale assemblies on surfaces
CSIC i-LINK+, LINKA20114
Carmen Ocal
01/2019 - 12/2020

Cooperation for the modification of natural surfaces and the molecular design of artificial surfaces with controlled ice nucleation properties
CSIC i-LINK+, LINKA20115
Albert Verdaguer
01/2019 - 12/2020

Fotoquímica y estabilidad de interfases modelo organico/agua para la descomposición del agua
Spanich Ministry of Science and Innovation FPI programme, PID2019-110907GB-I00
Carmen Ocal
2020 - 2023

Nuevas intercaras optimizadas para dispositivos responsivos basados en moléculas
MINECO - PROYECTOS I+D RETOS, MAT2016-77852-C2-1-R
Esther Barrena
2016 - 2020

Coordination
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Redaction
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Webmasters
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