Organic photovoltaic materials materials are attracting a great deal of attention due to a unique combination of sustainability aspects and chemical versatility. In this context, a new class of materials so-called non-Fullerene acceptors (NFA) blended with polymer-based donors are receiving a great deal of attention due to recent breakthroughs in the power conversion efficiency of the photovoltaic devices (current record is about 19%).
Such devices have the potential to play a key role on the development of a world energy matrix that is abundant, secure and environmentally friendly. However, a fundamental understanding of the underlying photophysics of the polymer:NFA blends is still lacking.
In this project, we are developing a multiscale modelling/simulation approach to address fundamental questions associated with the charge photogeneration and transport and to unveil the underlying structure-properties relationships. It will create a platform for in-silico design of novel organic photovoltaic materials (OPVs) and the first steps have already been taken in our current project (SNIC 2022/1-23) that will expire now in June. Thus, we are applied for resources for the continuation of the project. Within this framework, we are coupling molecular dynamics (MD) simulations with density functional theory (DFT) based calculations. The former cover two time and length scales, through the all-atom molecular dynamics (AAMD) and coarse-grained molecular dynamics (CGMD) simulations. A first parametrization of the force fields has been done and a benchmark of DFT calculation accuracy has been developed. Furthermore, the MD simulations have been coupled with the DFT calculations in a first case study of the acceptor PF5Y5. In this second stage, we will fully implement the sequential molecular dynamics/DFT approach and perform an extensive statistical analysis of the target properties. This will allow us to assess the relevant static and dynamical energetic disorder in the amorphous organic compounds. Mainly the electronic structure, optical properties and electronic transport will be computed computed and verified against experiment. The time-dependent DFT (TDDFT) will be used to describe the optical transitions and excited states. Concerning the target systems, the most representative NFAs (e.g. Y5, Y6, perylenes) and efficient polymer-donors (e.g. PBDB-T) will be investigated. Although similar methodology has been extensively employed to study solvated molecules (in liquid environment), it has not been applied for polymeric systems. Therefore, the development of such methodology for the OPVs is a novelty aspect of our proposal. To understand morphology formation at the mesoscopic scale, we have started with the development of a lattice model based on Monte Carlo simulations. However, the needed parameters have been obtained from experiments. However, the needed parameters have been obtained from experiments. In this second stage, we will couple the all-atom MD simulations with the lattice models to develop a truly multiscale methodology for the simulate the morphology formation. This project will be carried out in close collaboration with in-house experimental activities at Karlstad University. It will also be a collaboration between physics, chemistry and mathematics departments.