The Effect of Miscibility and Morphology of Porphyrin Donors and Non-Fullerene Acceptors on Exciton Dissociation Processes: A Quantum Chemical and Molecular Dynamics Study

Porphyrins and their derivatives have been employed extensively in organic solar cells (OSCs) in recent years. However, a deeper understanding of the exciton dissociation process for the porphyrin donor/non-fullerene acceptor (NFA) interface is still lacking. Herein, we have combined quantum chemistry and molecular dynamics simulations to explore the combination of mono and dimer porphyrin donors with various types of NFAs. The work reveals that the key issue lies in the exciton dissociation process of porphyrin materials, which have strong crystallinity to increase spacing (more than 5.0 angstrom), resulting in lesser miscibility and weaker intermolecular pi-pi stacking. The pathway for exciton dissociation will be limited by the small number of high-energy charge transfer (CT) states. To solve the above-mentioned issues, we implement an improved strategy for modifying the side chain of the terminal unit, reducing the stacking distance to 4.4 angstrom, while the number of CT states reaches up to 40 % (3/A3 style 1). Additionally, the results also indicate the development potential for all porphyrin OSCs, particularly, the charge recombination (k(CR)) rate of the 1/Rf-Iso system is lowered by nearly nine orders of magnitude. This research may offer fresh perspectives for extending the application range of porphyrin materials in OSCs.