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Title: New Insights into Dynamics and Morphology of P3HT:PCBM Active Layers in Bulk Heterojunctions

Abstract

Organic photovoltaics (OPVs) are topic of extensive research for their potential application in solar cells. Recent work has led to the development of a coarse-grained model for studying poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61-butyric acid methyl ester (PCBM) blends with molecular simulations. Here we provide further validation of the force field and use it to study the thermal annealing process of P3HT:PCBM blends. A key finding of our study is that, in contrast to a previous report, the annealing process does not converge at the short time scales reported. Rather, we find that the self assembly of the blends is characterized by three rate dependent stages that require much longer simulations to approach convergence. Using state-of-the- art high performance computing, we are able to study annealing at length and time scales commensurate with devices used in experiments. Our simulations show different phase segregated morphologies dependent on the P3HT chain length and PCBM volume fraction in the blend. For short chain lengths, we observed a smectic morphology containing alternate P3HT and PCBM domains. In contrast, a phase segregated morphology containing domains of P3HT and PCBM distributed randomly in space is found for longer chain lengths. Theoretical arguments justifying stabilization of these morphologiesmore » due to shape anisotropy of P3HT (rod-like) and PCBM (sphere-like) are presented. Furthermore, results on structure factor, miscibility of P3HT and PCBM, domain spacing and kinetics of phase segregation in the blends are presented in detail. Qualitative comparison of these results with small-angle neutron scattering experiments from literature is presented and an excellent agreement is found.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1110934
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Volume: 15; Journal Issue: 41; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY

Citation Formats

Carrillo, Jan-Michael Y., Kumar, Rajeev, Goswami, Monojoy, Sumpter, Bobby G., and Brown, W. Michael. New Insights into Dynamics and Morphology of P3HT:PCBM Active Layers in Bulk Heterojunctions. United States: N. p., 2013. Web. doi:10.1039/c3cp53271b.
Carrillo, Jan-Michael Y., Kumar, Rajeev, Goswami, Monojoy, Sumpter, Bobby G., & Brown, W. Michael. New Insights into Dynamics and Morphology of P3HT:PCBM Active Layers in Bulk Heterojunctions. United States. doi:10.1039/c3cp53271b.
Carrillo, Jan-Michael Y., Kumar, Rajeev, Goswami, Monojoy, Sumpter, Bobby G., and Brown, W. Michael. Fri . "New Insights into Dynamics and Morphology of P3HT:PCBM Active Layers in Bulk Heterojunctions". United States. doi:10.1039/c3cp53271b.
@article{osti_1110934,
title = {New Insights into Dynamics and Morphology of P3HT:PCBM Active Layers in Bulk Heterojunctions},
author = {Carrillo, Jan-Michael Y. and Kumar, Rajeev and Goswami, Monojoy and Sumpter, Bobby G. and Brown, W. Michael},
abstractNote = {Organic photovoltaics (OPVs) are topic of extensive research for their potential application in solar cells. Recent work has led to the development of a coarse-grained model for studying poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends with molecular simulations. Here we provide further validation of the force field and use it to study the thermal annealing process of P3HT:PCBM blends. A key finding of our study is that, in contrast to a previous report, the annealing process does not converge at the short time scales reported. Rather, we find that the self assembly of the blends is characterized by three rate dependent stages that require much longer simulations to approach convergence. Using state-of-the- art high performance computing, we are able to study annealing at length and time scales commensurate with devices used in experiments. Our simulations show different phase segregated morphologies dependent on the P3HT chain length and PCBM volume fraction in the blend. For short chain lengths, we observed a smectic morphology containing alternate P3HT and PCBM domains. In contrast, a phase segregated morphology containing domains of P3HT and PCBM distributed randomly in space is found for longer chain lengths. Theoretical arguments justifying stabilization of these morphologies due to shape anisotropy of P3HT (rod-like) and PCBM (sphere-like) are presented. Furthermore, results on structure factor, miscibility of P3HT and PCBM, domain spacing and kinetics of phase segregation in the blends are presented in detail. Qualitative comparison of these results with small-angle neutron scattering experiments from literature is presented and an excellent agreement is found.},
doi = {10.1039/c3cp53271b},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
issn = {1463-9076},
number = 41,
volume = 15,
place = {United States},
year = {2013},
month = {8}
}

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