Petascale Simulations of the Morphology and the Molecular Interface of Bulk Heterojunctions.
Understanding how additives interact and segregate within bulk heterojunction (BHJ) thin films is critical for exercising control over structure at multiple length scales and delivering improvements in photovoltaic performance. The morphological evolution of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blends that are commensurate with the size of a BHJ thin film is examined using petascale coarse-grained molecular dynamics simulations. Comparisons between two-component and three-component systems containing short P3HT chains as additives undergoing thermal annealing demonstrate that the short chains alter the morphology in apparently useful ways: they efficiently migrate to the P3HT/PCBM interface, increasing the P3HT domain size and interfacial area. Simulation results agree with depth profiles determined from neutron reflectometry measurements that reveal PCBM enrichment near substrate and air interfaces but a decrease in that PCBM enrichment when a small amount of short P3HT chains are integrated into the BHJ blend. Atomistic simulations of the P3HT/PCBM blend interfaces show a nonmonotonic dependence of the interfacial thickness as a function of number of repeat units in the oligomeric P3HT additive, and the thiophene rings orient parallel to the interfacial plane as they approach the PCBM domain. Using the nanoscale geometries of the P3HT oligomers, LUMO and HOMO energy levels calculated by density functional theory are found to be invariant across the donor/acceptor interface. These connections between additives, processing, and morphology at all length scales are generally useful for efforts to improve device performance.
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Jan-Michael Y
JM
Carrillo
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Zach
Z
Seibers
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Rajeev
R
Kumar
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Michael A
MA
Matheson
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
John F
JF
Ankner
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Monojoy
M
Goswami
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Kiran
K
Bhaskaran-Nair
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
William A
WA
Shelton
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
Bobby G
BG
Sumpter
Center for Nanophase Materials Sciences, ‡Computer Science and Mathematics Division, §National Center for Computational Sciences, and ∥Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Energy Science and Engineering and @Departments of Chemistry and Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Center for Computation and Technology and #Cain Department of Chemical Engineering Louisiana State University , Baton Rouge, Louisiana 70803, United States.
S Michael
SM
Kilbey
bulk heterojunction; coupled-cluster methods; donor/acceptor interface; molecular dynamics simulations; neutron reflectometry; organic photovoltaics; petascale simulations