Dresden 2017 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 55: Focus: Static and Dynamic Disorder Phenomena on the Transport in Organic Semiconductors I

CPP 55.4: Vortrag

Donnerstag, 23. März 2017, 11:45–12:00, ZEU 222

Dithienylethene as Switchable Hole Trap in Organic Semiconductors — •Tim Schaefer, Dirk Hertel, and Klaus Meerholz — Department of Chemistry, University of Cologne, Germany

Trap states can considerably hinder charge carrier transport. To better understand the influence of traps on the charge transport properties of organic semiconductors, we mix in traps on purpose. We present a unique hole trap, dithienlyethene (DTE), which can be photochemically switched "off" [1] to tune the trap concentration in one and the same device. DTE features two stable isomers that differ in HOMO energy. In a hole-conducting matrix with a certain HOMO energy, one DTE isomer acts as a hole trap, while the other isomer has a negligible influence on charge transport. The energetic trap depth is varied by blending DTE with various TPD-type hole conductors featuring different HOMO levels. In first proof-of-principle experiments, the hole mobility of the space-charge-limited current in a blend with DTE is reversibly switched by a factor of ca. 20. In contrast, in blends where DTE is replaced by a permanent trap with a similar trap depth trap-limited current is observed. Temperature dependent current density-voltage measurements and impedance spectroscopy are applied.

[1] R.C. Shallcross et al., Adv. Mater. 25, 469 (2013).