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Issue 41, 2013
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New insights into the dynamics and morphology of P3HT:PCBM active layers in bulk heterojunctions

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Abstract

Organic photovoltaics (OPVs) are a topic of extensive research because of 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 using 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 the 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 published small-angle neutron scattering experiments in the literature is presented and an excellent agreement is found.

Graphical abstract: New insights into the dynamics and morphology of P3HT:PCBM active layers in bulk heterojunctions

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Publication details

The article was received on 05 Aug 2013, accepted on 29 Aug 2013 and first published on 30 Aug 2013


Article type: Paper
DOI: 10.1039/C3CP53271B
Citation: Phys. Chem. Chem. Phys., 2013,15, 17873-17882
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    New insights into the dynamics and morphology of P3HT:PCBM active layers in bulk heterojunctions

    J. Y. Carrillo, R. Kumar, M. Goswami, B. G. Sumpter and W. M. Brown, Phys. Chem. Chem. Phys., 2013, 15, 17873
    DOI: 10.1039/C3CP53271B

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