Effect of Solvent Removal Rate and Annealing on the Interface Properties in a Blend of a Diketopyrrolopyrrole-Based Polymer with Fullerene

Abstract

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].

Quantum–Quantum and Quantum–Quantum-Classical Schemes for Near-Gap Excitations with Projection-Based-Embedded GW-Bethe–Salpeter Equation

“…A short C 2 H 2 group contained the branching point, and each branch is formed by C 4 H 9 , as can also be seen in Figure 1 (a). The geometry of this structure is cut from a snapshot of a large-scale classical Molecular Dynamics simulation of a DPP2Py m T polymer 16 and then relaxed in vacuum (DFT with the PBE0 functional and def2-TZVP basis) to a local minimum with nonsymmetric arrangement of the side chains. In (conjugated) polymer systems, it is often assumed that the frontier orbitals relevant for charge transport are localized on the actual functional backbone and that the side chains do not participate in the electronic processes.…”

“…4,11,12 Even though its scaling (dependent on details of the implementation) is favorable compared to wave function based methods such as ADC(2) 13 or CC2, 14 the direct application of GW-BSE to many complex molecular systems remains computationally challenging. Examples of such molecular systems are polymers with complex internal architecture, either solvated 15 or pure or mixed blends, 16 more general solvent−solute systems with nonequilibrium relaxation dynamics, 17 or molecular aggregates as in organic semiconductor films. 18 To make systems like these accessible, hybrid methods combining quantum and classical methods are often used, 4,17,19−27 sometimes combined with machine-learning models.…”

“…Over the past decade, it has gradually found more and more application in traditionally molecular quantum chemistry settings. − It was shown that GW -BSE provides an effective single- and two-particle picture with accurate energies for charged and neutral excitations of different character, e.g., photoionization and localized vs charge-transfer type excitations, without the need for any adaptations. ,, Even though its scaling (dependent on details of the implementation) is favorable compared to wave function based methods such as ADC(2) or CC2, the direct application of GW -BSE to many complex molecular systems remains computationally challenging. Examples of such molecular systems are polymers with complex internal architecture, either solvated or pure or mixed blends, more general solvent–solute systems with nonequilibrium relaxation dynamics, or molecular aggregates as in organic semiconductor films …”

Quantum-quantum and quantum-quantum-classical schemes with projection-based-embedded $GW$-Bethe--Salpeter Equation

“…Even though its scaling (dependent on details of the implementation) is favorable compared to wave-function based methods such as ADC(2) 9 or CC2 10 , the direct application of GW -BSE to many complex molecular systems remains computationally challenging. Examples for such molecular systems are polymers with complex internal architecture, either solvated 11 or pure or mixed blends 12 , more general solvent-solute systems with nonequilibrium relaxation dynamics 13 , or molecular aggregates as in organic semiconductor films 14 .…”