Dr. Jaime Martín Semi-Paracrystalline Organization in Semiconducting Polymers for Photovoltaics

Guest talk

Precise determination of structural organization of semiconducting polymers is of paramount importance for the further development of these materials in organic electronic technologies, as solid-state microstructure and optoelectronic properties are highly interlinked. Yet, prior characterization of some of the best-performing materials for transistor and photovoltaic applications often resulted in conundrums in which X-ray scattering and microscopy yielded seemingly contradicting results. In this presentation I will argue that the paradox above stems from the fact the microstructure of these materials does not seem to fit with stablished structural models for polymers, i.e. the amorphous, semi-crystalline and paracrystalline models, and, hence, these polymers require the introduction of a new structural organization model. Therefore, we introduced the semi-paracrystalline model. The semi-paracrystalline model establishes that the microstructure of these materials contains a dense array of small paracrystalline domains and more disordered regions. Thus, unlike other structural models, the overall structural order relies on two parameters: the novel concept of degree of paracrystallinity (i.e., paracrystalline volume/mass fraction) and the lattice distortion parameter of paracrystalline domains (g-parameter from X-ray scattering). I will show that charge carrier transport in semi-paracrystalline materials is particularly sensitive to the interconnection of paracrystalline domains. Because the semi-paracrystalline microstructure seems to be a common feature among many semiconducting polymers, these results can have profound implications in the broad organic electronics arena, where device operation models and device optimization protocols must now include the semi-paracrystalline organization.

BIO:
Graduated from the Institute of Polymer Science and Technology of CSIC (Spain) and trained at Imperial College London (UK), Jaime Martín is a Ramon y Cajal Researcher at University of La Coruña (Spain), where he leads the Group of Functional Polymer Materials, which is devoted to understanding the solid-state microstructure of conjugated polymers and how this is connected with their properties. He also holds a visiting Ikerbasque position at POLYMAT in San Sebastián (Spain). With an H-index of 31, his scientific outcomes have resulted in more than 70 papers, including the Mater. Horizons Outstanding Paper Award of 2022 and an invited paper for the Rising Star series of Adv. Mater. 2021. Jaime´s research activities are combined with an intense teaching duty (240 h per year)

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