Multi-scale modeling of poly(3-hexylthiophene) and [6,6]-phenyl-c61-butyric acid methyl ester using coarse grained force field derived from DFT based atomistic force field

Abstract

The power conversion efficiencies for the organic photovoltaic cells containing active layers of electron donors and acceptors are dependent of three morphological properties, namely the domain size of the electron donor phase, the interface-to-volume ratio of the blend and the percolation ratio. In this study, poly(3-hexylthiophene) (P3HT), poly(3-nonylthiophene) (P3NT), poly(3-dodecylthiophene) (P3DT), fullerene (C60) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends have been introduced as the active layers to understand the effect of the structural deformation of the active layer components on the morphological properties. The state-of-the-art coarse grained molecular dynamics simulations are employed to investigate the morphological properties of the active layer systems. We have developed Morse potential-based force field parameters to accurately describe potential energy surfaces between C60 and P3HT coarse grained models. Using the coarse-grained model, we can investigate much larger system during longer simulation time than using full atomistic model. We modified the electron donor and acceptor materials and analyzed how the modifications affect the morphological quantities of active layer in both microscopic macroscopic scales with weight ratio of 1:1.