We study from first principles the electronic, optical, and vibrational properties of organic semiconductors, in the gas-phase, in solution, and in their aggregated and crystalline forms.

Key questions in our studies concern the nature of the excitations in oranic materials and the role of charge transfer therein.  For this purpose, we use (time-dependent) density-functional theory and many-body perturbation theory (GW/BSE). 

For review, see C. Cocchi, M. Guerrini, J. Krumland, N.T. Nguyen, and A. M. Valencia, Modeling the electronic structure of organic materials: A solid-state physicist's perspective, J. Phys: Materials, 6, 012001 (2022).

Funded projects

• FoMEDOS (DFG, 2017-2019)

Relevant publications

• N. Russegger, A. M. Valencia, L. Merten, M. Zwadlo, G. Duva, L. Pithan, A. Gerlach, A. Hinderhofer, C. Cocchi, and F. Schreiber, Molecular Charge Transfer Effects on Perylene Diimide Acceptor and Dinapthothienothiophene Donor Systems, J. Phys. Chem. C, 126, 4188 (2022).
• A. E. Mansour,* A. M. Valencia,* D. Lungwitz, B. Wegner, N. Tanaka, Y. Shoji, T. Fukushima, A. Opitz, C. Cocchi, and N. Koch, Understanding the evolution of the Raman spectra of molecularly p-doped poly(3-hexylthiophene-2,5-diyl): signatures of polarons and bipolarons, PCCP  24, 3109 (2022).
• M. Guerrini, A. M. Valencia, and C. Cocchi, Long-Range Order Enhances Charge Transfer in Donor/Acceptor Co-Crystals, J. Phys. Chem. C., 125, 20821 (2021).
• D. Gründer*, A. M. Valencia*, M. Guerrini, T. Breuer, C. Cocchi, and G. Witte, Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Co-Crystalline Films: Limits of Non-Periodic Modelling, J. Phys. Chem. Lett., 12, 9899 (2021).
• C. Zeiser, L. Moretti, T. Geiger, L. Kalix, A. M. Valencia, M. Maiuri, C. Cocchi, H. F. Bettinger, G. Cerullo, and K. Broch, Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene, J. Phys. Chem. Lett. 12, 7453 (2021).
• C. P. Theurer, A. M. Valencia, J. Hausch, C. Zeiser, V. Sivanesan, C. Cocchi, P. Tegeder, and K. Broch, Photophysics of charge transfer complexes formed by tetracene and strong acceptors, J. Phys. Chem. C 125, 6313 (2021).
• J. Krumland, A.M. Valencia, and C. Cocchi, Exploring organic semiconductors in solution: The effects of solvation, alkylization, and doping, PCCP 23, 4841 (2021).
• M. Arvind, C. E. Tait, M. Guerrini, J. Krumland, A. M. Valencia, C. Cocchi, A. E. Mansour, N. Koch, S. Barlow, S. R. Marder, J. Behrends, D. Neher, Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution, J. Phys. Chem. B 124, 7694 (2020).
• R. Schier, A. M. Valencia, and C. Cocchi, Microscopic Insight into the Electronic Structure of BCF-Doped Oligothiophenes from Ab initio Many-Body Theory, J. Phys. Chem. C 124, 14363–14370 (2020).
• A. E. Mansour, D. Lungwitz, T. Schultz, M. Arvind, A. M. Valencia, C. Cocchi, A. Opitz, D. Neher, and N. Koch, The optical signatures of molecular-doping induced polarons in poly(3-hexylthiophene-2,5-diyl): individual polymer chains versus aggregates, J. Chem. Mater. C 8, 2870 (2020).
• A. M. Valencia, M. Guerrini, and C. Cocchi, Ab initio modelling of local interfaces in doped organic semiconductors, Phys. Chem. Chem. Phys. 22, 3527 (2020).
• A. M. Valencia and C. Cocchi, Electronic and optical properties of oligothiophene-F4TCNQ charge-transfer complexes: The role of donor conjugation length, J. Phys. Chem. C 129, 9317 (2019).
• M. Guerrini, C. Cocchi, A. Calzolari, D. Varsano, and S. Corni, Interplay between intra- and inter-molecular charge transfer in the optical excitations of J-aggregates, J. Phys. Chem. C 123, 6831 (2019).
• P. Beyer, D. Pham, C. Peter, N. Koch, E. Meister, W. Brütting, L. Grubert, S. Hecht, D. Nabok, C. Cocchi, C. Draxl, and A. Opitz, State of matter dependent charge transfer interactions between planar molecules for doping applications, Chem. Mater. 31, 1237 (2019). 
• C. Cocchi, T. Breuer, G. Witte, and C. Draxl, Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs, Phys. Chem. Chem. Phys.  20, 29724 (2018).