Quasiparticles and Band Structures in Organized Nanostructures of Donor–Acceptor Copolymers

Abstract

The performance of organic semiconductor devices is linked to highly ordered nanostructures of self-assembled molecules and polymers. Many-body perturbation theory is employed to study the excited states in bulk copolymers. The results show that acceptors in the polymer scaffold introduce a, hitherto unrecognized, conduction impurity band that leads to electron localization. The donor states are responsible for the formation of conjugated bands, which are only mildly perturbed by the presence of the acceptors. Along the polymer axis, the nonlocal electronic correlations among copolymer strands hinder efficient band transport, which is, however, strongly enhanced across individual chains. Holes are most effectively transported along the π−π stacking, while electrons in the impurity band follow the edge-to-edge directions. The copolymers exhibit regions with inverted transport polarity, in which electrons and holes are efficiently transported in mutually orthogonal directions.

Halogen–Halogen Bonded Donor-Acceptor Stacks Foster Orthogonal Electron and Hole Transport

“…The orthogonal ambipolar transport has been reported in heterogeneous mixtures of n-type small molecule and p-type polymer and was recently theoretically predicted within D-A copolymers. 23,24 In line with our persistent pursuit of designing crystalline supramolecular scaffolds possessing highly sought-after emergent properties, 25,26 herein we report the unique slip-stacked duplex assembly of a covalently connected organic donoracceptor (D-A) system comprising stabilizing Br•••Br halogen bonding interactions, evocative of the base-paired nonhelical structure of double-stranded DNA (Figure 1). The character-istic slip-stacked arrangement of the D-A moieties and halogen-halogen interactions are observed to promote orthogonal maximal hole and electron transport.…”

Efficient treatment of molecular excitations in the liquid phase environment via stochastic many-body theory

“…To overcome the high cost of conventional implementations, we employ the recently developed stochastic formalism, which can be applied to extremely large systems owing to its linear scaling. 56,[58][59][60][61][62][63][64]77 This approach to the oneshot perturbative correction (typically denoted G 0 W 0 ) seeks the QP energy by randomly sampling the single-particle states and decomposing the operators in the real-time domain. The stochastic formalism has been described in detail in previous work [61][62][63] and it is briefly revisited in the SI.…”

“…In principle, the GF formalism fully captures QPs and their lifetimes, and it is widely applied to condensed matter problems. [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] Further, the methodology is open for systematic improvements; embedding within the GF framework 21,43,47,48,54,60 is conceptually straightforward and "seamless." Finally, recent developments of stochastic GF methods [60][61][62][63][64] enabled calculations for giant systems with thousands of electrons, practically treating large and inhomogeneous systems on equal footing.…”

Viewpoints on the 2020 Virtual Conference on Theoretical Chemistry

“…The resulting stochastic GW method is highly scalable and is capable of simulating large systems containing tens of thousands of electrons. Dr. Vlček and co-workers applied the stochastic GW approach to study highly delocalized quasiparticle excitations in twisted bilayers, heterostructures of low dimensional semiconductors, and donor–acceptor copolymers . Dr. Vlček further presented a methodological advancement where vertex corrections are included in the stochastic evaluation of self-energy .…”

“…Dr. Vlcěk and co-workers applied the stochastic GW approach to study highly delocalized quasiparticle excitations in twisted bilayers, 58 heterostructures of low dimensional semiconductors, 59 and donor−acceptor copolymers. 60 Dr. Vlcěk further presented a methodological advancement where vertex corrections are included in the stochastic evaluation of self-energy. 61 The resulting stochastic GWΓ formalism is shown to yield accurate quasiparticle energies for a series of organic molecules.…”