Sequence-Controlled Electron Transport in Conjugated Copolymers

Chemical sequence control is a powerful means for modifying the physical properties of conjugated polymers, with alternating, gradient, block, and random copolymer motifs being commonly employed. Here, we combine a Markov process treatment of copolymer sequence correlations with electron transport models spanning three regimes to understand how the conjugated copolymer sequence influences electronic mobility. Within the delocalized polaron hopping and electronically coherent transport regimes, electronic mobility is a nonmonotonic function of the sequence correlation parameter λ, which smoothly interpolates between alternating (λ = -1), ideally random (λ = 0), and blocky copolymer (0 < λ < 1) architectures. Alternating and blocky copolymer sequences exhibit higher mobilities than random sequences, though within the localized polaron hopping regime, mobility displays only a weak dependence on sequence. Our theoretical approach also facilitates a controlled analysis of how sequence defects in alternating copolymers impact electronic mobility, demonstrating that one sequence defect per ∼100 repeat units can be sufficient to negate the ostensible benefits of an alternating copolymer architecture for increasing electron mobilities.