TYC Soiree: simulation of photo-excited and charge transport processes in organic semiconductors

Name: TYC Soiree: simulation of photo-excited and charge transport processes in organic semiconductors
Start: 2025-11-05T15:30:00+00:00
End: 2025-11-05T17:00:00+00:00
Location: Leolin Price Lecture Theatre in UCL GOSICH – Wellcome Trust Bldg

5 November 2025 @ 3:30 pm – 5:00 pm

TYC Soiree: simulation of photo-excited and charge transport processes in organic semiconductors Share on X

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Atomistic insights into the photodynamics of organic crystals and nanoclusters – Federico Hernandez, QMUL

Exciton Delocalization and Dynamics: From Light Absorption to Charge Separation in Molecular Aggregates – Samuele Giannini, University of Pisa

Light absorption, charge separation, and electronic transport are vital for optimizing optoelectronic devices and designing new materials, yet a fundamental understanding remains challenging because these processes span multiple time, length, and morphological scales. Quantum phenomena—arising from coupled electronic and vibrational (vibronic) interactions—govern both the optical response and electronic transport in supramolecular aggregates and molecular semiconductors.1,2

I will show how first-principles-based Hamiltonians, parametrized for realistic, energetically disordered material morphologies and incorporating localized and charge transfer states, can explain aggregation-induced changes in steady-state optical spectra.3,4 By coupling these Hamiltonians with both full quantum dynamics and mixed quantum–classical dynamics, we characterize the nature and evolution of electronic excitations across a broad range of timescales. Ultrafast dynamics in dense vibronic manifolds are resolved using efficient Multiconfigurational Time Dependent Hartree wavepacket propagation, while a surface-hopping approach in the excitonic-state basis enables simulations at longer times.

Our results clarify the role of exciton delocalization and coherence5 in enhancing the efficiency of important electronic processes such as charge separation in molecular aggregates6 and provide structure–property relationships that inform the design of more efficient optoelectronic devices.

References:

1. Giannini, S. et al. Exciton transport in molecular organic semiconductors boosted by transient quantum delocalization. Nat. Commun. 13, 2755 (2022).
2. Giannini, S. et al. Transiently delocalized states enhance hole mobility in organic molecular semiconductors. Nat. Mater. 22, 1361–1369 (2023).
3. Giannini, S. et al. On the Role of Charge Transfer Excitations in Non-Fullerene Acceptors for Organic Photovoltaics. Mater. Today 80, 308–326 (2024).
4. Giannini, S., Cerdá, J., Prampolini, G., Santoro, F. & Beljonne, D. Dissecting the nature and dynamics of electronic excitations in a solid-state aggregate of a representative non-fullerene acceptor. J. Mater. Chem. C 12, 10009–10028 (2024).
5. Giannini, S., Segalina, A., Padula, D., Cantina, M. & Pastore, M. Disentangling Delocalization and Coherence in Photoexcited Noisy Supramolecular Aggregates. (submitted 2025)
6. Ivanovic, F., Peng, W.-T., Giannini, S., Blumberger, J. Transiently Delocalised Hybrid Quantum States are the Gateways for Efficient Exciton Dissociation at Organic Donor-Acceptor Interfaces. (2025) https://doi.org/10.21203/rs.3.rs-7059572/v1.