Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 14: Poster: Interfaces and Thin Films
CPP 14.10: Poster
Montag, 22. März 2010, 16:30–18:00, Poster C
Electrical properties of a charge-transfer interlayer modified organic heterojunction — •Shuwen Yu1, Ingo Salzmann1, Antje Vollmer2, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Institut f. Physik, Brook-Taylor-Str. 6, 12489 Berlin — 2HZB-BESSY, Albert-Einstein-Str. 15, 12489 Berlin
We investigated the effect of a thin interlayer (ca. monolayer) of tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) between prototypical hole and electron transport layers (HTL and ETL) on interface energetics and current transport. As HTL we used 4,4',4''-tris(N,N-diphenyl-amino)triphenylamine (TDATA) and tris (8-hydroxyquinoline)aluminium (Alq3) as ETL, which are commonly employed in organic light emitting diodes. The hole injection barrier into TDATA is 0.5 eV, as measured by photoemission spectroscopy. Deposition of an F4-TCNQ interlayer on top of TDATA does not further change the energy level position. However, after applying the F4-TCNQ interlayer the energy levels of Alq3 deposited on top of TDATA are 0.15 eV closer to the Fermi-level than without the interlayer. Diodes fabricated without interlayer had a 0.6 V higher onset-voltage one order of magnitude lower current density than those with F4-TCNQ. These observations can be rationalized by an increased (non-radiative) electron-hole recombination rate at the modified organic heterojunction and a changed internal electric field distribution.