Mode-selective ab-initio photoinduced dynamics in conjugated polymers

Project Information

MOSAIC

Grant agreement ID: 101155733

DOI

10.3030/101155733

Project terminated on 14 September 2025

EC signature date 13 May 2024

Start date 1 July 2024

End date 30 June 2026

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 211 754,88

Coordinated by

UNIVERSITE DE TOULOUSE
France

Periodic Reporting for period 1 - MOSAIC (Mode-selective ab-initio photoinduced dynamics in conjugated polymers)

Reporting period: 2024-07-01 to 2026-06-30

Summary of the context and overall objectives of the project

Sunlight is abundant, but figuring out how to efficiently grab that energy and convert it into something useful, like electricity for our homes, is a big puzzle. This research project dives into the world of a special type of molecules called "π-conjugated polymers." We can think of them as microscopic antennas that are really good at absorbing sunlight, particularly the colors we see. For instance, there are star-shaped molecules called dendrimers that are incredibly efficient at collecting energy and funneling it to a central point. Moreover, these polymers are building blocks for new kinds of materials that could advance technologies like screens, electronics, and solar panels.

This project focuses on specific sunlight-absorbing molecules that act as models for understanding the behavior of more complex materials that could be used in technological applications. We want to understand exactly how the energy moves around inside these molecules after they absorb light. This involves figuring out how the molecule's structure influences this energy transfer. To do this, we'll use powerful computer simulations.

One of the goals is to go beyond standard ways of simulating these molecules and incorporate quantum effects in the simulations. In the quantum world, things don't always behave as we expect in our everyday lives. By tackling the complex quantum dynamics of energy transfer in these molecules, scientists hope to get a more accurate picture of how the energy behaves. They'll also explore if it's possible to control this energy flow using carefully designed light pulses.

The significance of this project lies in its focus on the fundamental science that underpins these technologies. Think of this project as laying the groundwork for a new generation of energy-harvesting and electronic materials. The insights gained will provide a roadmap for chemists and materials scientists to design and synthesize new organic materials with tailored properties for better solar cells, advanced electronics, and artificial light-harvesting systems. This research will pave the way for more efficient and sustainable energy solutions for the future.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The MOSAIC project has advanced the state-of-the-art in computational modelling of the tunable optical, structural, and dynamical properties of π-conjugated polymers critical to organic optoelectronics. The most relevant scientific output are the detailed atomistic simulations of the photo-induced response in artificial light-harvesting molecular antennas, and the computation of their transient absorption pump–probe (TA-PP) spectra. The TA-PP spectra monitors energy relaxation and redistribution in real time, and provide a detailed microscopic picture of the relevant energy-transfer pathways. We believe this represents the first reported on-the-fly atomistic simulation of TA-PP signals for such a large molecular system. Our modelling shows that internal conversion processes are mediated by a specific set of middle- to high-frequency normal modes, which directly influence the spatial exciton redistribution along the polymer backbone.

Further results offer atomistic insight into the influence of quantum effects on observed spectra for hydrogen molecules in cage-like carbon nanostructures. We computed the temperature dependence of energy spectra of hydrogen molecules trapped in fullerene cages of varying size and geometry (Cn, n=24,28,60,70) within a wide range of thermodynamics conditions (i.e. from T=130K to T=320K), and we discussed the possible influence of these properties on the hydrogen storage capacity of these materials.

Furthermore, we developed and implemented the mapping of quantum dynamics onto classical-like dynamics in an extended phase space. This methodology was benchmarked for the photoinduced dissociative dynamics of the collinear van der Waals complex NeBr2(B,ν), which is challenging to access experimentally using modern pump-probe spectroscopy techniques. This novel approach will enable to perform efficient trajectory-based simulations of tunable exciton dynamics in more complex donor-acceptor architectures.

The project delivered a deeper knowledge on the properties of technologically relevant OCMs, which could be subsequently used to conceive more efficient nanoscale devices.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The MOSAIC project addressed the urgent need for sustainable energy solutions by advancing our understanding of the microscopic mechanisms underlying energy harvesting in organic conjugated materials (OCMs). OCMs exhibit strong absorption in the visible sunlight spectrum, which makes them promising candidates for artificial light harvesting. The latter is considered a key strategy to address the increasing demand for affordable, eco-friendly, and sustainable energy sources.

While traditional classical molecular dynamics simulations often fail to capture the nuances of light-matter interactions in these systems, the MOSAIC project successfully pursued the development of advanced computational models to simulate exciton dynamics in large π-conjugated polymers. The work carried out at the Laboratory of Collisions, Aggregates, Reactivity involved simulating non-adiabatic excited-state dynamics to track energy redistribution pathways through the polymer network following light absorption. The project provided new insights into how specific vibrational modes facilitate or hinder exciton transport, enabling predictive calculations of exciton migration in large conjugated systems.

The progress made has enabled to increase the size of complex molecular architectures for organic electronics that can be simulated atomistically. Furthermore, ab initio molecular dynamics simulations of the transient absorption spectra of large molecular systems of interest for optoelectronic applications were carried out for the first time. In addition, substantial progress was made in incorporating the influence of excitation pulse shapes on exciton dynamics in conjugated polymers. This work is essential for optimizing the efficiency of next-generation organic solar cells and light-harvesting technologies. The MOSAIC project contributed in this way to bridging the gap between fundamental molecular structure and macroscopic energy transfer performance.