When Molecules Assemble: Multi-Scale Modeling Perspectives on the Electronic States of Bulk Non-Fullerene Acceptors

Leandro R. Franco^a^,^b^,^c, Mateus Bergami^a, Rafael B. Ribeiro^a^,^b^,^d, Danillo Valverde^e, Alexandre Holmes^b, Cleber Marchiori^a, Márcio T. do N. Varella^d, Ellen Moons^a, Ergang Wang^b, Moyses Araujo^a^,^f

^aDepartment of Engineering and Physics, Karlstad University, Sweden

^bDepartment of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden.

^cLaboratory for Chemistry of Novel Materials, University of Mons, Belgium.

^dInstitute of Physics, University of São Paulo, Brazil.

^eNamur Institute of Structured Matter, University of Namur, Belgium.

^fMaterials Theory Division, Department of Physics and Astronomy, Uppsala University, Sweden.

Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV26)

Uppsala, Sweden, 2026 May 18th - 20th

Organizers: Gerrit Boschloo, Ellen Moons, Feng Gao and Anders Hagfeldt

Invited Speaker Session, Moyses Araujo, presentation 145
Publication date: 11th March 2026

A fundamental understanding of the photophysics of organic photovoltaics (OPVs) at the molecular level remains a major challenge, limiting the rational design of novel materials with enhanced performance and stability. To help bridge this knowledge gap, we developed a multi-scale methodology that integrates Quantum Mechanics (QM) calculations with Classical Molecular Dynamics (CMD) simulations in a sequential QM/CMD framework to investigate OPV photophysics under realistic conditions¹. Our approach begins with CMD simulations of macromolecules (oligomer models) in solution, followed by the simulation of film formation via solvent removal. Further CMD simulations are then conducted on the resulting films to generate statistically uncorrelated configurations for subsequent QM calculations. These calculations are carried out using density functional theory (DFT), time-dependent DFT (TD-DFT), and the wavefunction-based ADC(2) method, with environmental effects considered either explicitly with an electrostatic embedding scheme or implicitly with a polarizable embedding model. We have applied this multi-scale methodology to study (i) the PF5-Y5 polymer, serving as a model system for covalently bound donor-acceptor interfaces and (ii) Y6 and Y6-derived acceptors. Our analysis quantifies the effects of molecular dynamics and environment on electronic transitions, providing an improved description of optical absorption and redox properties. In particular, we find that the intrinsic asymmetry of Y-type acceptors induces distinct local electronic environments, which significantly influence the relative energetic positioning and character of singlet and triplet excited states. Such insight is essential, for instance, to assess triplet-mediated oxygen sensitization and material degradation, a topic of significant concern. Overall, this study highlights the critical role of disorder, dynamics, and molecular environment effects in determining the electronic properties of ground and excited states of OPV materials, offering insights for the design of next-generation photovoltaic systems.

References:

[1] Franco, L.R.; Valverde, D; Marchiori, C.; Moons, E.; Wang, E; Araujo, M. Multiscale modeling of structural disorder and environmental effects on the ground and excited states properties of a conjugated donor–acceptor polymer in the bulk phase. Journal of Physics: Energy 2025, 7, 045001

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