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Tuning Exciton diffusion through Charge-Transfer Excitations in Supramolecular Assemblies

Project description

Study on how energy moves in optoelectronic devices to boost efficiency

How energy moves in an organic semiconductor – energy migration – is essential for improving optoelectronic devices such as solar cells. This process involves singlet excitons – bound electron-hole pairs – that travel a certain distance before decaying. Increasing exciton diffusion lengths could significantly boost device efficiency. With the support of the Marie Skłodowska-Curie Actions programme, the TECTESA project aims to deepen understanding of the influence of inter-molecular charge-transfer excitations, which can either enhance exciton movement or hinder it by forming energy traps. By combining advanced simulations and realistic modelling, researchers aim to uncover how these charge-transfer effects shape exciton behavior. Researchers will develop a new transport framework and apply it to promising materials like polymer fibres and molecular acceptors.

Objective

Energy migration, by which bound electron-hole pairs (i.e. singlet excitons) travel through an organic semiconductor before decaying, is at the heart of functioning optoelectronic devices such as solar cells. Designing materials with large singlet exciton diffusion lengths Ld would strongly benefit the efficiency of such devices. In this context, recent reports in highly ordered polymeric fibers and non-fullerene acceptor thin films of Ld largely exceeding the typical 10-20nm values call for a detailed microscopic picture going beyond the usual (hopping) models. Among others, a key missing ingredient in most modelling studies so far deals with the role of inter-molecular charge-transfer (CT) excitations. These have the potential to magnify the exciton dispersion at the band bottom or act as gateways for long-range energy migration, but could equally be detrimental to transport due to the formation of low-lying energy traps. In TECTESA, we aim at providing an in-depth mechanistic analysis of singlet exciton diffusion in organic molecular semiconductors in presence of CT configurations, highlighting namely their contrasting effects on the shape of the thermally accessible excitonic density of states and the coupling to the nuclear degrees of freedom. To reach this ambitious goal, we will: (i) develop and implement a universal transport formalism based on mixed classical-quantum non-adiabatic molecular dynamic simulations that explicitly accounts for CT excitations; (ii) explore how intermolecular CT configurations affect the nature and dynamics of singlet excitons in reduced models, through a broad range of physical situations (from superexchange to hybridization and trapping); and (iii) apply our newly developed approach to study energy migration in realistic, fully atomistic, models for N-heterotriangulene supramolecular fibers and non-fullerene Y6 molecular acceptors, where preliminary investigations seem to intimate the presence of low-lying CT pairs.

Fields of science (EuroSciVoc)

Programme(s)

Topic(s)

Funding Scheme

HORIZON-TMA-MSCA-PF-EF - HORIZON TMA MSCA Postdoctoral Fellowships - European Fellowships

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Call for proposal

(opens in new window) HORIZON-MSCA-2022-PF-01

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Coordinator

UNIVERSITE DE MONS
Net EU contribution
€ 175 920,00
Address
PLACE DU PARC 20
7000 Mons
Belgium
Region
Région wallonne Prov. Hainaut Arr. Mons
Activity type
Higher or Secondary Education Establishments
Links
Total cost
No data