The nature of optical excitations and the spatial extent of excitons in organic semiconductors, both of which determine exciton diffusion and carrier mobilities, are key factors for the proper understanding and tuning of material performances. Using a combined experimental and theoretical approach, we investigate the excitonic properties of meso-tetraphenyl porphyrin-Zn(II) crystals. We find that several bands contribute to the optical absorption spectra, beyond the four main ones considered here as the analogue to the four frontier molecular orbitals of the Gouterman model commonly adopted for the isolated molecule. By using many-body perturbation theory in the GW and Bethe–Salpeter equation approach, we interpret the experimental large optical anisotropy as being due to the interplay between long- and short-range intermolecular interactions. In addition, both localized and delocalized excitons in the π-stacking direction are demonstrated to determine the optical response, in agreement with recent experimental observations reported for organic crystals with similar molecular packing.

Palummo, M., Raimondo, L., Hogan, C., Goletti, C., Trabattoni, S., Sassella, A. (2021). Nature of Optical Excitations in Porphyrin Crystals: A Joint Experimental and Theoretical Study. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 12(2), 869-875 [10.1021/acs.jpclett.0c03581].

Nature of Optical Excitations in Porphyrin Crystals: A Joint Experimental and Theoretical Study

Raimondo, Luisa
Secondo
;
Trabattoni, Silvia
Penultimo
;
Sassella, Adele
Ultimo
2021

Abstract

The nature of optical excitations and the spatial extent of excitons in organic semiconductors, both of which determine exciton diffusion and carrier mobilities, are key factors for the proper understanding and tuning of material performances. Using a combined experimental and theoretical approach, we investigate the excitonic properties of meso-tetraphenyl porphyrin-Zn(II) crystals. We find that several bands contribute to the optical absorption spectra, beyond the four main ones considered here as the analogue to the four frontier molecular orbitals of the Gouterman model commonly adopted for the isolated molecule. By using many-body perturbation theory in the GW and Bethe–Salpeter equation approach, we interpret the experimental large optical anisotropy as being due to the interplay between long- and short-range intermolecular interactions. In addition, both localized and delocalized excitons in the π-stacking direction are demonstrated to determine the optical response, in agreement with recent experimental observations reported for organic crystals with similar molecular packing.
Articolo in rivista - Articolo scientifico
porphyrins, organic thin films, exciton delocalization, electronic properties, zinc meso-tetraphenylporphyrin, charge-trasfer excitons, Wannier-Mott excitons, Frenkel excitons, π-stacking, many-body perturbation theory, absorption spectra, optical anisotropy;
English
11-gen-2021
2021
12
2
869
875
open
Palummo, M., Raimondo, L., Hogan, C., Goletti, C., Trabattoni, S., Sassella, A. (2021). Nature of Optical Excitations in Porphyrin Crystals: A Joint Experimental and Theoretical Study. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 12(2), 869-875 [10.1021/acs.jpclett.0c03581].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/300043
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