title: Energy Level Alignment at Metal/Solution-Processed Organic Semiconductor Interfaces.
abstract: Energy barriers between the metal Fermi energy and the molecular levels of organic semiconductor devoted to charge transport play a fundamental role in the performance of organic electronic devices. Typically, techniques such as electron photoemission spectroscopy, Kelvin probe measurements, and in-device hot-electron spectroscopy have been applied to study these interfacial energy barriers. However, so far there has not been any direct method available for the determination of energy barriers at metal interfaces with n-type polymeric semiconductors. This study measures and compares metal/solution-processed electron-transporting polymer interface energy barriers by in-device hot-electron spectroscopy and ultraviolet photoemission spectroscopy. It not only demonstrates in-device hot-electron spectroscopy as a direct and reliable technique for these studies but also brings it closer to technological applications by working ex situ under ambient conditions. Moreover, this study determines that the contamination layer coming from air exposure does not play any significant role on the energy barrier alignment for charge transport. The theoretical model developed for this work confirms all the experimental observations.
authors.affiliation: CIC nanoGUNE, 20018, Donostia-San Sebastian, Basque Country, Spain.
authors.forename: Ainhoa
authors.initials: A
authors.lastname: Atxabal
authors.affiliation: Department of Chemistry and Biology, Linkoping University, 58183, Linkoping, Sweden.
authors.forename: Slawomir
authors.initials: S
authors.lastname: Braun
authors.affiliation: Institute for Materials Science, Dresden University of Technology, 01062, Dresden, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Arnold
authors.affiliation: CAS Center for Excellence in Nanoscience, Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China.
authors.forename: Xiangnan
authors.initials: X
authors.lastname: Sun
authors.affiliation: CIC nanoGUNE, 20018, Donostia-San Sebastian, Basque Country, Spain.
authors.forename: Subir
authors.initials: S
authors.lastname: Parui
authors.affiliation: Department of Chemistry and Biology, Linkoping University, 58183, Linkoping, Sweden.
authors.forename: Xianjie
authors.initials: X
authors.lastname: Liu
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU, 20018, Donostia-San Sebastian, Basque Country, Spain.
authors.forename: Cristian
authors.initials: C
authors.lastname: Gozalvez
authors.affiliation: CIC nanoGUNE, 20018, Donostia-San Sebastian, Basque Country, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Llopis
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU, 20018, Donostia-San Sebastian, Basque Country, Spain.|IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Basque Country, Spain.
authors.forename: Aurelio
authors.initials: A
authors.lastname: Mateo-Alonso
authors.affiliation: CIC nanoGUNE, 20018, Donostia-San Sebastian, Basque Country, Spain.|IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Basque Country, Spain.
authors.forename: Felix
authors.initials: F
authors.lastname: Casanova
authors.affiliation: Institute for Materials Science, Dresden University of Technology, 01062, Dresden, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Ortmann
authors.affiliation: Department of Chemistry and Biology, Linkoping University, 58183, Linkoping, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Fahlman
authors.affiliation: CIC nanoGUNE, 20018, Donostia-San Sebastian, Basque Country, Spain.|IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Basque Country, Spain.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Hueso
keywords: energy barriers; hot electron transistors; organic electronics; polymer; spectroscopy