title: Steric control of the donor/acceptor interface: implications in organic photovoltaic charge generation.
abstract: The performance of organic photovoltaic (OPV) devices is currently limited by modest short-circuit current densities. Approaches toward improving this output parameter may provide new avenues to advance OPV technologies and the basic science of charge transfer in organic semiconductors. This work highlights how steric control of the charge separation interface can be effectively tuned in OPV devices. By introducing an octylphenyl substituent onto the investigated polymer backbones, the thermally relaxed charge-transfer state, and potentially excited charge-transfer states, can be raised in energy. This decreases the barrier to charge separation and results in increased photocurrent generation. This finding is of particular significance for nonfullerene OPVs, which have many potential advantages such as tunable energy levels and spectral breadth, but are prone to poor exciton separation efficiencies. Computational, spectroscopic, and synthetic methods were combined to develop a structure-property relationship that correlates polymer substituents with charge-transfer state energies and, ultimately, device efficiencies.
authors.affiliation: Department of Chemistry, University of California Berkeley, Berkeley, California 94720-1460, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Holcombe
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Norton
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rivnay
authors.forename: Claire H
authors.initials: CH
authors.lastname: Woo
authors.forename: Ludwig
authors.initials: L
authors.lastname: Goris
authors.forename: Claudia
authors.initials: C
authors.lastname: Piliego
authors.forename: Gianmarco
authors.initials: G
authors.lastname: Griffini
authors.forename: Alan
authors.initials: A
authors.lastname: Sellinger
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas
authors.forename: Alberto
authors.initials: A
authors.lastname: Salleo
authors.forename: Jean M J
authors.initials: JM
authors.lastname: Fréchet