title: Tailor-made additives for morphology control in molecular bulk-heterojunction photovoltaics.
abstract: Tailor-made additives, which are molecules that share the same molecular structure as a parent molecule with only slight structural variations, have previously been demonstrated as a useful means to control crystallization dynamics in solution. For example, tailor-made additives can be added to solutions of a crystallizing parent molecule to alter the crystal growth rate, size, and shape. We apply this strategy as a means to predictably control morphology in molecular bulk-heterojunction (BHJ) photovoltaic cells. Through the use of an asymmetric oligomer substituted with a bulky triisobutylsilyl end group, the morphology of BHJ blends can be controlled resulting in a near doubling (from 1.3 to 2.2%) in power conversion efficiency. The use of tailor-made additives provides promising opportunities for controlling crystallization dynamics, and thereby film morphologies, for many organic electronic devices such as photovoltaics and field-effect transistors.
authors.affiliation: Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611-7200, United States. Grahamk@stanford.edu
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Graham
authors.forename: Romain
authors.initials: R
authors.lastname: Stalder
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Wieruszewski
authors.forename: Dinesh G Dan
authors.initials: DG
authors.lastname: Patel
authors.forename: Danielle H
authors.initials: DH
authors.lastname: Salazar
authors.forename: John R
authors.initials: JR
authors.lastname: Reynolds