title: Exciton dynamics reveal aggregates with intermolecular order at hidden interfaces in solution-cast organic semiconducting films.
abstract: Large-scale organic electronics manufacturing requires solution processing. For small-molecule organic semiconductors, solution processing results in crystalline domains with high charge mobility, but the interfaces between these domains impede charge transport, degrading device performance. Although understanding these interfaces is essential to improve device performance, their intermolecular and electronic structure is unknown: they are smaller than the diffraction limit, are hidden from surface probe techniques, and their nanoscale heterogeneity is not typically resolved using X-ray methods. Here we use transient absorption microscopy to isolate a unique signature of a hidden interface in a TIPS-pentacene thin film, exposing its exciton dynamics and intermolecular structure. Surprisingly, instead of finding an abrupt grain boundary, we reveal that the interface can be composed of nanoscale crystallites interleaved by a web of interfaces that compound decreases in charge mobility. Our novel approach provides critical missing information on interface morphology necessary to correlate solution-processing methods to optimal device performance.
authors.affiliation: Department of Chemistry, University of California, D64 Hildebrand Hall, Berkeley, California 94720, USA.
authors.forename: Cathy Y
authors.initials: CY
authors.lastname: Wong
authors.affiliation: Department of Chemistry, University of California, D64 Hildebrand Hall, Berkeley, California 94720, USA.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Cotts
authors.affiliation: Department of Chemistry, University of California, D64 Hildebrand Hall, Berkeley, California 94720, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.affiliation: 1] Department of Chemistry, University of California, D64 Hildebrand Hall, Berkeley, California 94720, USA [2] Department of Physics, University of California, D64 Hildebrand Hall, Berkeley, California 94720, USA [3] Physical Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [4] Kavli Energy NanoSciences Institute, Berkeley, California 94720, USA.
authors.forename: Naomi S
authors.initials: NS
authors.lastname: Ginsberg