Soft Matter Café (Organised by the PSCM) : Rachel KILBRIDE Avik DAS

Shedding Light on Organic Semiconductors: Understanding Self-Assembly with Neutron and X-ray Scattering (by Rachel KILBRIDE , XMaS/BM28, Synchrotron Radiation Facility, Grenoble, France)

Organic semiconductors, including conjugated polymers and small molecules combine lightweight, flexible, and solution-processable properties with highly tunable electronic characteristics. By precisely designing their molecular structure, these materials can be tailored for a wide range of thin-film optoelectronic technologies, from organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), photon-multipliers, sensors and more. However, achieving optimal performance and stability in these devices depends critically on the ability to control self-assembly and film structure across multiple length scales, from molecular-scale packing to nanoscale phase separation and mesoscale ordering.

In this talk, I will present examples from my research, highlighting the use of neutron and X-ray scattering techniques - including grazing-incidence wide-angle X-ray scattering (GIWAXS), small-angle neutron scattering (SANS), and neutron reflectometry (NR) - to probe the self-assembly of organic semiconductors thin films for next-generation solar energy technologies. Firstly, I will show how these powerful techniques can be used to probe the relationships between processing <> structure <> performance <> stability in polymer:small molecule blends for OPVs. Secondly, I will introduce nanocomposite films comprising organic semiconductors and inorganic quantum dots as effective photon-multiplier systems for enhanced solar energy harvesting. Here, I will show how thermal processing is a promising route to controlling the dispersion of QDs within organic semiconductor matrices leading to optimized film morphologies. Combined, these insights offer new understandings and routes to achieving efficient, stable, and scalable solar energy technologies.

About the speaker: Rachel Kilbride is a post-doctoral researcher on the XMaS/ B28 beamline at the ESRF studying the self-assembly of soft matter and energy materials. Before joining the ESRF, she completed her PhD in Physics at the University of Sheffield (UK), focusing on the characterization of organic photovoltaic blends followed by a post-doctoral position in the chemistry department to develop nanocomposite ‘photon-multiplier’ films for enhanced energy harvesting. Her research to date focuses on the use of neutron and X-ray scattering techniques to understand structure-property relationships in a range of emerging optoelectronic systems.

Structural insight and initial formation kinetics of interpolyelectrolyte complex made of polysaccharides: Small-Angle Scattering perspective (by Avik DAS, Postdoctoral research associate at Technische Universität Berlin, Germany)

The rapid mixing of aqueous solutions of oppositely charged polyelectrolytes (PEs) triggers the instantaneous formation of interpolyelectrolyte complexes (IPECs), driven by the release of counterions. Given their broad range of potential applications—including drug delivery, food science, and biotechnology—IPECs have attracted significant attention in recent years. Their structure is intricately linked to the molecular architecture of the PEs involved and the complex interplay between electrostatic interactions and various thermodynamic factors, which remain to be fully understood in fundamental physicochemical terms. Additionally, there is very limited information on the kinetic aspects of IPEC formation, particularly during the initial stages and subsequent reconfiguration, which ultimately determine the growth and final structure of these complexes. In this talk, I will highlight how small-angle scattering techniques were employed to model the intricate structure of IPECs and extract quantitative insights into their formation kinetics.    

About the speaker: Avik Das earned his Ph.D. in Physical Sciences from Bhabha Atomic Research Centre, Mumbai, India, where he later joined as a staff scientist. He is currently on sabbatical leave, pursuing postdoctoral research at the Stranski Laboratory, Technische Universität Berlin, under the supervision of Prof. Michael Gradzielski. His expertise lies in small-angle scattering technique, with a research focus on designing and developing a modular sample environment for studying soft matter systems under non-equilibrium conditions. He is currently investigating the formation kinetics and structural properties of polyelectrolyte complexes.  

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