Features in ultrafast relaxation dynamics following near/mid-UV excitations of PC<sub>61</sub>BM molecule
POSTER
Abstract
Polymer functionalized fullerenes, namely, phenyl-C61 butyric acid methyl ester (PC61BM), are prospective electron acceptors in fullerene-based photovoltaics [1,2]. Photoexcited (hot) electrons in these molecules may meander by transiently relocating among the fullerene, ester and phenyl sub-region along the relaxation pathway. In general, with the non-adiabatic coupling between excited (virtual) orbitals being weaker/stronger leads to longer/shorter delay in the overall relaxation process. Our results indicate significant increase in relaxation times, versus those of C60, following near- and mid-ultraviolet light driven excitations to some (lower) LUMO orbitals. This is likely an effect of polymerized functionalization. We use electron-phonon coupled nonadiabatic molecular dynamics [3,4] to simulate the relaxation process. The method depends on a combination of the single-particle description in density functional theory (DFT) and fewest-switches surface hopping approach using the Libra software [5]. We intend to present some preliminary results of our efforts in using advanced machine learning (ML) techniques [6] to produce ab initio level of accuracy in reduced time and cost.
References:
[1] G.J. Hedley et al, Nat. Commun. 4, 2867 (2013).
[2] C.-Z. Li et al, J. Mater. Chem. 22, 4161, (2012).
[3] “Ultrafast transfer and transient entrapment of photoexcited Mg electron in Mg@C60”; M.E. Madjet, E. Ali, M. Carignano, O. Vendrell, and H.S. Chakraborty, Phys. Rev. Lett. 126, 183002 (2021).
[4] “Ultrafast nonadiabatic electron dynamics in photoexcited C60: a comparative study among DFT exchange-correlation functionals”; E. Ali, M.E. Madjet, R. De, M.B. Wholey, T. Frauenheim, and H.S. Chakraborty, J. Phys. Chem. A 129, 2123 (2025).
[5] M. Shakiba et al, Software Impacts 14 100445 (2022).
[6] “Machine-Learned Kohn–Sham Hamiltonian Mapping for Nonadiabatic Molecular Dynamics”; M. Shakiba and A.V. Akimov, J. Chem. Theory Comput. 20, 2992 (2024).
References:
[1] G.J. Hedley et al, Nat. Commun. 4, 2867 (2013).
[2] C.-Z. Li et al, J. Mater. Chem. 22, 4161, (2012).
[3] “Ultrafast transfer and transient entrapment of photoexcited Mg electron in Mg@C60”; M.E. Madjet, E. Ali, M. Carignano, O. Vendrell, and H.S. Chakraborty, Phys. Rev. Lett. 126, 183002 (2021).
[4] “Ultrafast nonadiabatic electron dynamics in photoexcited C60: a comparative study among DFT exchange-correlation functionals”; E. Ali, M.E. Madjet, R. De, M.B. Wholey, T. Frauenheim, and H.S. Chakraborty, J. Phys. Chem. A 129, 2123 (2025).
[5] M. Shakiba et al, Software Impacts 14 100445 (2022).
[6] “Machine-Learned Kohn–Sham Hamiltonian Mapping for Nonadiabatic Molecular Dynamics”; M. Shakiba and A.V. Akimov, J. Chem. Theory Comput. 20, 2992 (2024).
*National Science Foundation Grant Nos. PHY-2110318 and PHY-2512850. BARTIK High-Performance Cluster at Northwest Missouri State University (National Science Foundation Grant No. CNS-1624416). Services provided by the PATh Facility, which is supported by the National Science Foundation Award No. 1836650
Presenters
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Ruma De
- Northwest Missouri State University