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Proceedings Paper

Identifying interfacial charge transfer states in organic heterostructures (Conference Presentation)
Author(s): Andreas P Arndt; Marina Gerhard; Ian A. Howard; Martin Koch; Ulrich Lemmer

Paper Abstract

Charge transfer (CT) states play evidently an important role at the interface of organic heterostructures but their identification and characterization is often experimentally less obvious and challenging. We studied two exemplary material systems which both represented a benchmark within the research of organic photovoltaics at their time: the homopolymer P3HT blended with PC61BM and the copolymer PTB7 blended with PC71BM. In both heterostructures, we could identify a distinct CT state emission by the use of NIR time-resolved photoluminescence (PL) [1], [2]. The selectivity of this technique enables us to clearly probe the energetics and dynamics of weak emitting interfacial states and therefore to prove differences in the CT state characteristics between the two systems. We went beyond this previous work and investigated the time and temperature dependent emission anisotropy as well as the electric field dependence of the time-resolved PL for both blends and the pristine polymers, respectively. In both cases the CT state emission clearly deviates from the one of the primarily excited singlet excitons: the emission anisotropy reveals an additional relaxation pathway for the exciton which is connected with a change of the transition dipole moment of the emission, and under applied bias different quenching thresholds can give access to varying binding energies of the emissive excitons involved. Finally, we think that our findings demonstrate how interfacial CT state emission can be clearly identified as such and how it can be unambiguously distinguished from singlet exciton emission.

Paper Details

Date Published: 10 November 2016
PDF: 1 pages
Proc. SPIE 9923, Physical Chemistry of Interfaces and Nanomaterials XV, 99231G (10 November 2016); doi: 10.1117/12.2238126
Show Author Affiliations
Andreas P Arndt, Karlsruher Institut für Technologie (Germany)
Marina Gerhard, Philipps-Univ. Marburg (Germany)
Ian A. Howard, Karlsruher Institut für Technologie (Germany)
Martin Koch, Philipps-Univ. Marburg (Germany)
Ulrich Lemmer, Karlsruher Institut für Technologie (Germany)


Published in SPIE Proceedings Vol. 9923:
Physical Chemistry of Interfaces and Nanomaterials XV
Artem A. Bakulin; Robert Lovrincic; Natalie Banerji, Editor(s)

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