title: Design rules for organic donor-acceptor heterojunctions: pathway for charge splitting and detrapping.
abstract: Organic solar cells rely on the conversion of a Frenkel exciton into free charges via a charge-transfer state formed on a molecular donor-acceptor pair. These charge-transfer states are strongly bound by Coulomb interactions and yet efficiently converted into charge-separated states. A microscopic understanding of this process, though crucial to the functionality of any solar cell, has not yet been achieved. Here we show how long-range molecular order and interfacial mixing generate homogeneous electrostatic forces that can drive charge separation and prevent minority carrier trapping across a donor-acceptor interphase. Comparing a variety of small-molecule donor-fullerene combinations, we illustrate how tuning of molecular orientation and interfacial mixing leads to a trade-off between photovoltaic gap and charge-splitting and detrapping forces, with consequences for the design of efficient photovoltaic devices.
authors.affiliation: †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.|‡Heidelberg Graduate School of Fundamental Physics, INF 226, 69120 Heidelberg, Germany.
authors.forename: Carl
authors.initials: C
authors.lastname: Poelking
authors.affiliation: †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Denis
authors.initials: D
authors.lastname: Andrienko