Sundaram V, Lyulin AV, Baumeier B. Effect of Solvent Removal Rate and Annealing on the Interface Properties in a Blend of a Diketopyrrolopyrrole-Based Polymer with Fullerene.
J Phys Chem B 2022;
126:7445-7453. [PMID:
36122390 PMCID:
PMC9527757 DOI:
10.1021/acs.jpcb.2c04609]
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Abstract
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We study the effect of solvent-free annealing and explicit
solvent
evaporation protocols in classical molecular dynamics simulations
on the interface properties of a blend of a diketopyrrolopyrrole (DPP)
polymer with conjugated substituents (DPP2Py2T) and PCBM[60]. We specifically
analyze the intramolecular segmental mobility of the different polymer
building blocks as well as intermolecular radial and angular distribution
functions between donor and acceptor. The annealing simulations reveal
an increase of the glass-transition temperature of 45 K in the polymer–fullerene
blend compared to that of pure DPP2Py2T. Our results show that the
effective solvent evaporation rates at room temperature only have
a minor influence on the segmental mobility and intermolecular orientation,
characterized in all cases by a preferential arrangement of PCBM[60]
close to the electron-donating substituents in DPP2Py2T. In contrast,
solvent-free annealing from a liquid yields clustering of the fullerene
close to the electron-withdrawing DPP, generally considered to be
detrimental for application in organic solar cells. We find that the
difference can be attributed to differences in the behavior of 2-hexyldecyl
side-chains, which collapse toward DPP when solvent is explicitly
removed, thereby blocking access of PCBM[60].
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