Share Email Print

Proceedings Paper

IR spectroscopic studies of charge transfer in organic semiconductors
Author(s): Sebastian Beck; David Gerbert; Christian Krekeler; Tobias Glaser; Annemarie Pucci
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

Charge transfer (CT) mechanisms are crucial for device performance in organic electronics, but they are still not understood on a fundamental level. Here we want to show that in situ IR spectroscopy is very well suited to investigate CT effects in organic semiconductors in a qualitative and quantitative way. We study the ambipolar transport material 4,4´-bis(N-carbazolyl)-1,1´-biphenyl (CBP) as matrix and cesium carbonate (Cs2CO3) as n-dopant. To achieve doped layers, both materials were evaporated simultaneously. The system is one of the rare ones for n-doping of organic layers. In the spectra of the doped layers, additional absorption bands appear in the mid IR range. These can be assigned to the negatively charged matrix molecules that indicate electron transfer. The charged molecules exhibit these different absorption bands, as the charge transfer leads to a change in bond length and bond strength of the molecules. Our results very well agree with density functional theory calculations of the vibrational spectra of both, charged and non-charged molecules. By fitting the spectra of the doped layers as a superposition of the vibrational oscillators of neutral and charged species, we were able to quantify the amount of charged matrix molecules and to determine the doping efficiency of the investigated systems. For CBP n-doped with Cs2CO3 a hindrance of the CT due to air exposure could be observed.

Paper Details

Date Published: 1 May 2014
PDF: 6 pages
Proc. SPIE 9137, Organic Photonics VI, 91370T (1 May 2014); doi: 10.1117/12.2054203
Show Author Affiliations
Sebastian Beck, Univ. Heidelberg (Germany)
InnovationLab GmbH (Germany)
David Gerbert, Univ. Heidelberg (Germany)
InnovationLab GmbH (Germany)
Christian Krekeler, InnovationLab GmbH (Germany)
Technische Univ. Braunschweig (Germany)
Tobias Glaser, Ruprecht-Karls-Univ. Heidelberg (Germany)
InnovationLab GmbH (Germany)
Annemarie Pucci, Ruprecht-Karls-Univ. Heidelberg (Germany)
InnovationLab GmbH (Germany)
Ruprecht-Karls-Univ. Heidelberg (Germany)

Published in SPIE Proceedings Vol. 9137:
Organic Photonics VI
Barry P. Rand; Chihaya Adachi; David Cheyns; Volker van Elsbergen, Editor(s)

© SPIE. Terms of Use
Back to Top