Molecular Insights into the Mechanical Properties of Polymer–Fullerene Bulk Heterojunctions for Organic Photovoltaic Applications

Abstract

We investigate the mechanical properties of π-conjugated polymeric materials composed of regioregular poly(3-hexylthiophene) (P3HT) and fullerene C60 using coarse-grained molecular dynamics simulations. Specifically, we perform tensile simulations of P3HT:C60 composites with varied degrees of polymerization and C60 mass fractions to obtain their stress-strain responses.Decomposition of stress tensor into kinetic energy and virial contributions indicates that the tensile moduli of the pure P3HT samples are greatly dependent on non-bonded interactions and on bonded interactions associated with bond-stretching, while the addition of C60 leads to an increase in the tensile modulus originating from enhanced non-bonded interactions associated with C60. Additionally, the tensile strength of the P3HT:C60 samples correlates well with molecular chain entanglements, which are characterized by the average number of kinks per chain obtained from primitive path analysis. We also find that the upper and lower yield points characterizing strain softening become more pronounced with increasing C60 mass fraction.Persistent homology analysis indicates that the emergence of the yield points correlates well with the coalescence of microvoids in the course of tensile deformation, resulting in the generation of larger voids. These results provide a fundamental understanding of the molecular determinants of the mechanical properties of π-conjugated polymer-fullerene composites, which can also help to interpret and predict the mechanical properties of other polymer composites containing fullerene.

Gas Adsorption and Diffusion Behaviors in Interfacial Systems Composed of a Polymer of Intrinsic Microporosity and Amorphous Silica: A Molecular Simulation Study

“…Nonetheless, our findings suggest that the presence of silica surfaces results in different diffusion behaviors of gases in the vicinity of PIM-1/silica interfaces, providing intriguing molecular insights that are unobtainable by experiments. Finally, we opine that, to model more realistic MMMs considering the dispersion of aggregated nanoparticles in a PIM-1 matrix, a coarse-grained (CG) MD technique would be an attractive choice because CGMD allows for simulation at a much larger spatiotemporal scale than can be achieved with all-atom MD. − However, the CG force field requires precise parametrization to reproduce the static/dynamic properties of interest.…”

Persistent Homology Analysis for Materials Research and Persistent Homology Software: HomCloud

“…In the case of polymer systems, the correlation with material properties is actively discussed rather than the extraction of the structure itself, compared to the two examples mentioned above. For example, correlations with dielectric con-stant, 37) shear response, 38) and crazing process 39) were discovered. As a study that focuses on the structure itself, a method to quantify the threading of ring polymers has been proposed.…”

“…Of course, other data than materials science is also available. HomCloud has been already used in various scientific researches, including materials science, 17,34,35,37,38,40,[61][62][63][64][65][66][67][68] geology, 20,69) structural biology, 70) and medical image analysis. 71,72) HomCloud has useful functionalities such as visualization, inverse analysis, machine learning.…”

Delicate crystallinity control enables high-efficiency P3HT organic photovoltaic cells

“…Though these P3HT:nonfullerene blends are still less efficient compared with the high-efficiency OPV systems, the innovations in molecular structure design of nonfullerene acceptors have still provided a lot of new opportunities for device optimization and demonstrated the huge potential of P3HT-OPV systems. 29–32…”