Blends of poly(3-alkylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester for organic photovoltaic cell applications: Multi-scale modeling approach

Abstract

The interface-to-volume ratio of the structure and the transport property of the charge careers are the two main factors affecting the photovoltaic cell performance. In this study, the blends of poly(3-alkylthiophene) (P3AT) (A denotes H, N, and D for hexyl, nonyl, and dodecyl, respectively) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are investigated to understand the effect of the variation of molecular structure of the thiophene-based polymer in the active layer on the two main factors. First, we develop well-designed coarse-grained models to efficiently describe P3AT-PCBM systems. Next, the coarse-grained molecular dynamics simulations are performed to investigate the structural properties of three coarse-grained active layer systems, P3AT-PCBM. We conclude from our simulated analysis that the P3HT-PCBM system will provide the structurally optimized condition for the best photovoltaic cell performance. This is evidenced by two observations: (1) P3HT exhibits a good contact with PCBM in molecular level and (2) the P3HT-PCBM system forms a well-organized molecular network in each of the electron donor and accepter phases.