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Supervisors:  Prof. Maurizio Persico and Dr. Giovanni Granucci

Title:  Computational simulation of the singlet fission process in organic crystals

Abstract:
Singlet fission (SF) is a fast (sub-picosecond) process in which the lowest excited singlet state (S1) of a chromophore transfers parts of its energy to the neighbouring chromophore (S0) resulting in two (local) triplets that are coupled into a singlet (1TT). It can be beneficial for increasing the power conversion efficiency of organic photovoltaic cells. It exploits the high-energy photon and generates multiple electron-hole pairs that are capable for charge separation, therefore it minimises the thermal energy loss. The elucidation of SF mechanism is crucial for the development of new and highly efficient SF chromophores. The potential energy surfaces of relevant photoexcited states and the couplings between chromophores give rise to the static picture of the SF mechanism. They have been investigated during the first one-and-half year of the project at the University of Groningen. The investigation has been performed employing the nonorthogonal configuration interaction method in which the electronic couplings between photoexcited diabatic states have been calculated directly while remaining a clear chemical interpretation of the photoexcited states involved. In addition, the simulations of the nonadiabatic dynamics with the trajectory surface hopping method will be performed during the second one-and-half year of the project at the University of Pisa. The crystal structure of the potential chromophores for SF will be treated at QM/MM level where the QM subsystem will be one of the possible dimers. The dimers that show the strongest couplings between the lowest photoexcited singlet and the 1TT states will be chosen for the simulation. This nonadiabatic dynamics simulation will be analysed to elucidate the SF mechanism and other competing processes that may lower the SF quantum yield.

Publications:
1.    Meilani Wibowo, Ria Broer, and Remco W. A. Havenith, A rigorous nonorthogonal configuration interaction approach for the calculation of electronic couplings between diabatic states applied to singlet fission, Computational and Theoretical Chemistry 2017. DOI: 10.1016/bs.aiq.2017.03.005.
2.    Marco Garazzi*, Meilani Wibowo*, Hugo Gattuso, Elise Dumont, Daniel Roca-Sanjuán, and Antonio Monari, Hydrogen abstraction by photoexcited benzophenone: consequences for DNA photosensitization, Physical Chemistry Chemical Physics 2016, 18, 7829-7836. DOI: 10.1039/c5cp07938a. * Contributed equally.
3.    Elise Dumont, Meilani Wibowo, Daniel Roca-Sanjuán, Marco Garavelli, Xavier Assfeld, and Antonio Monari, Resolving the benzophenone DNA-photosensitization mechanism at QM/MM level, Journal of Physical Chemistry Letter 2015, 6, 576-580. DOI: 10.1021/jz502562d.

Oral communications at congress:
1.    Chemistry for the Future 2017, Pisa, Italy, 5 - 7 July 2017.
Title of oral communication: Singlet fission mechanism: A theoretical study.
2.    CHAINS (Chemistry As Innovating Science), the Dutch chemistry conference, Veldhoven, the Netherlands, 6 - 8 December 2016.
Title of oral communication: Nonorthogonal configuration interaction for calculating singlet fission efficiency.
3.    1st Annual Workshop ITN-EJD-TCCM, Université Pierre et Marie Curie, Paris, France, 18 - 20 July 2016.
4.    Singlet Fission Workshop, Peaceful Valley Ranch and Conference Center, Lyons, Colorado, USA, 18 - 21 June 2016.
Title of oral communication: Nonorthogonal configuration interaction for the study of singlet fission.

Poster communications at congress:
1.    WATOC2017, Munich, Germany, 27 August - 1 September 2017.
Title of poster: Calculations of electronic couplings applied in the singlet fission process.
Authors: Meilani Wibowo, Ria Broer, Maurizio Persico, and Remco W. A. Havenith.
2.    Next-Gen III: PV Materials, Oosterpoort, Groningen, the Netherlands, 2 - 5 July 2017.
Title of poster: Elucidation of the singlet fission mechanism: A theoretical study.
Authors: Meilani Wibowo, Ria Broer, and Remco W. A. Havenith.
3.    Vlieland Meeting 2017, Vlieland, the Netherlands, 7 - 9 May 2017.
Title of poster: Elucidation of the singlet fission mechanism: A theoretical study.
Authors: Meilani Wibowo, Ria Broer, and Remco W. A. Havenith.
4.    Physics@Veldhoven 2017, Veldhoven, the Netherlands, 17 - 18 January 2017.
Title of poster: Nonrthogonal configuration interaction for the study of singlet fission.
Authors: Meilani Wibowo, Ria Broer, and Remco W. A. Havenith.
5.    (Co-author) 10th Congress on Electronic Structure: Principles and Applications ESPA 2016, Castellón de la Plana, Spain, 28 June - 1 July 2016.
Title of poster: Spectroscopic and Photophysical Properties of Porphycene: A RASPT2 Study.
Authors: Mercedes Rubio, Meilani Wibowo, Antonio Mas, and Daniel Roca-Sanjuán.
6.    CHAINS (Chemistry As Innovating Science), the Dutch chemistry conference, Veldhoven, the Netherlands, 30 November - 2 December 2015.
Title of poster: Computational approaches to study materials for higher efficiency organic photovoltaics.
Authors: Meilani Wibowo, María Izquierdo, Ria Broer, and Remco W. A. Havenith.