Do you want to keep up to date? Subscribe to our newsletter. 1mail every 2months! |
 |
The study is published at Materials Horizons and one of its images have been selected for the cover of the April volume of the magazine, showing semi-conducting polymers.
Cerdanyola del Vallès, 8th April 2022 Semi-conducting polymers are a new generation of materials with enormous interest for organic electronic technologies, including transistors and photovoltaic applications. However, up to now, the structural characterization of these materials has led to contradictory results, resulting in a flagrant lack of knowledge of their actual solid-state microstructure.
The historical classification of polymers labels these materials as amorphous, semicrystalline and paracrystalline. An amorphous polymer consists of randomly oriented molecules. In contrast, semi-crystalline polymers combine amorphous regions with crystalline regions, in which chain segments are stacked in lamellar crystallites. Finally, paracrystalline polymers comprise a molecular lattice with significant amounts of disordering and no amorphous regions. However, most advanced semiconducting polymers do not seem to fit in any of the above mentioned groups.
To solve this condundrum, researchers introduced a new structural model for polymer materials: the semi-paracrystalline model. This model asserts that semi-conducting polymers are a class of materials where small paracrystalline domains coexist with more disordered regions. This new model allows reliable description of the solid-state microstructure of semi-conducting polymer materials.
Unlike previous structural models, the semi-paracrystalline model developed by Sara Marina and Jaime Martin, from the University of A Coruña and POLYMAT, require two parameters to account for the overall degree of order: the paracrystallinity distortion parameter, which accounts for the lattice disorder within paracrystals, and the degree of paracrystallinity, which measures the mass/volume fraction of ordered material.
The characteristics of the semi-crystalline microstructure, such as its morphology and structure parameters, were inferred from the combination of X-ray diffraction techniques, differential scanning calorimetry and optical, electronic and force microscopies. Specifically, grazing incidence wide and small angle X-ray scattering (GIWAXS and GISAXS) were performed at the NCD-SWEET beamline of the ALBA Synchrotron.
A precise determination of structural organization of semi-conducting polymers is of paramount importance for the further development of these materials in organic electronic technologies as optoelectronic properties are intimately linked to the molecular arrangement. Main application of semi-paracrystalline semi-conducting polymers are organic photovoltaic cells, whose main difference with the traditional ones is that the active layer is composed of organic semiconducting molecules. As a result, the manufacturing process is simplified and the cost of production is reduced.
Reference: Sara Marina, Edgar Gutierrez-Fernandez, Junkal Gutierrez, Marco Gobbi, Nicolás Ramos, Eduardo Solano, Jeromy Rech, Wei You, Luis Hueso, Agnieszka Tercjak, Harald Ade and Jaime Martin. Scaling Up the Production of Semi-paracrystallinity in semi-conducting polymers. Materials Horizons (2021). DOI: 10.1039/d1mh01349a
With the collaboration of Fundación Española para la Ciencia y la Tecnología. The ALBA Synchrotron is part of the of the Unidades de Cultura Científica y de la Innovación (UCC+i) of the FECYT and has received support through the FCT-20-15798 project.
