Title:	Atomic-scale modelling and simulation of charge transfer process and photodegradation in Organic Photovoltaics
DNr:	SNIC 2020/5-664
Project Type:	SNIC Medium Compute
Principal Investigator:	Ellen Moons <ellen.moons@kau.se>
Affiliation:	Karlstads universitet
Duration:	2021-01-01 – 2022-01-01
Classification:	10304 10302 10402
Homepage:	https://www.kau.se/en/researchers/ellen-moons
Keywords:

Abstract

The main goal of this project is to assess fundamental aspect of the charge photogeneration in organic Donor:Acceptor interfaces commonly used in Organic photovoltaic devices (OPV) as well as the initial stages of the photodegradation process that take place when those organic materials are in their excited state in presence of oxygen. This is to be achieved combining molecular dynamics simulations and density functional theory (DFT) based calculations. The project will be conducted in synergy with the experimental counterpart, allowing a deeper understanding of the photophysics and photochemistry of organic materials as well as validating the new theoretical methodologies which will be developed. Organic materials (OM), for sustainable energy generation are a promising alternative, which bring together the following aspects: (i) they can be produced from abundant raw materials and (ii) they are highly versatile displaying tunable properties that can meet end-user-specific demands[1]. However, there are drawbacks associated with their stability and recombination processes which are the source of energy losses limiting the photon-to-electric current conversion. [2,3] The idea is to use supercomputers to virtually study copolymers and small-molecules in atomistic scale, by DFT, ab-initio molecular dynamics (AIMD) and evolutionary algorithm (EA) to resolve the crystal structure of small-molecules commonly used as electron acceptor in OPVs. By employing those theoretical tools, the electronic structure of the isolated materials and Donor:Acceptor complexes as well as the optical and electronic properties can be assessed and directly compared with experimental outcomes (such as UV-Vis Absorption and IR spectra redox activity and spectroscopical profiles, viz. UPS and XPS). However, the proper assessment of such properties demands an effective sampling of chain conformations and molecular orientation in order to properly describe pairwise interaction and the chemical environment where charge separation/recombination or photoinduced degradation take place The computational time requested here will be used to develop a sequential approach for polymer modelling, starting with a molecular approach to select the chain length for the oligomeric structures followed by an AIMD simulation to describe the interchain interactions and the thin film formation culminating with the single chain or cluster model selection for which an in-depth DFT study will be carried out. The DFT calculations will be carried out using Gaussian[4], Orca[5], VASP[6]; and for the evolutionary algorithm we will use the USPEX software[7]. References: (1) Häupler, B.; Wild, A.; Schubert, U.S. Adv. Energy Mater. 2015, 5 (11). (2) Fan,Q. et al., Energy Environ. Sci., 2020, Advance Article, DOI: 10.1039/D0EE01828G. (3) V. Blazinic, V.; Ericsson, L.K.E.; Muntean, S. A.; Moons, E. Synthetic Metals 2018 26–3027 (241). (4) http://gaussian.com (5) https://wiki.gnome.org/Projects/Orca (6) https://www.vasp.at (7) https://uspex-team.org/en