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Charge Transfer Absorption and Emission at ZnO/Organic Interfaces

  • We investigate hybrid charge transfer states (HCTS) at the planar interface between a-NPD and ZnO by spectrally resolved electroluminescence (EL) and external quantum efficiency (EQE) measurements. Radiative decay of HCTSs is proven by distinct emission peaks in the EL spectra of such bilayer devices in the NIR at energies well below the bulk a-NPD or ZnO emission. The EQE spectra display low energy contributions clearly red-shifted with respect to the a-NPD photocurrent and partially overlapping with the EL emission. Tuning of the energy gap between the ZnO conduction band and a-NPD HOMO level (E-int) was achieved by modifying the ZnO surface with self-assembled monolayers based on phosphonic acids. We find a linear dependence of the peak position of the NIR EL on E-int, which unambiguously attributes the origin of this emission to radiative recombination between an electron on the ZnO and a hole on a-NPD. In accordance with this interpretation, we find a strictly linear relation between the open-circuit voltage and the energy of theWe investigate hybrid charge transfer states (HCTS) at the planar interface between a-NPD and ZnO by spectrally resolved electroluminescence (EL) and external quantum efficiency (EQE) measurements. Radiative decay of HCTSs is proven by distinct emission peaks in the EL spectra of such bilayer devices in the NIR at energies well below the bulk a-NPD or ZnO emission. The EQE spectra display low energy contributions clearly red-shifted with respect to the a-NPD photocurrent and partially overlapping with the EL emission. Tuning of the energy gap between the ZnO conduction band and a-NPD HOMO level (E-int) was achieved by modifying the ZnO surface with self-assembled monolayers based on phosphonic acids. We find a linear dependence of the peak position of the NIR EL on E-int, which unambiguously attributes the origin of this emission to radiative recombination between an electron on the ZnO and a hole on a-NPD. In accordance with this interpretation, we find a strictly linear relation between the open-circuit voltage and the energy of the charge state for such hybrid organicinorganic interfaces.show moreshow less

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Metadaten
Author:Fortunato Piersimoni, Raphael Schlesinger, Johannes Benduhn, Donato Spoltore, Sina Reiter, Ilja Lange, Norbert Koch, Koen Vandewal, Dieter NeherORCiDGND
DOI:https://doi.org/10.1021/jz502657z
ISSN:1948-7185 (print)
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=26261970
Parent Title (English):The journal of physical chemistry letters
Publisher:American Chemical Society
Place of publication:Washington
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Volume:6
Issue:3
Pagenumber:5
First Page:500
Last Page:504
Funder:German Research Foundation (DFG) [SFB 951, SPP 1355]; German Federal Ministry for Education and Research (BMBF); Helmholtz-Energie-Allianz "Hybridphotovoltaik"
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert