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Determination of triplet excitons in organic semiconductor materials

Published online by Cambridge University Press:  22 January 2014

S. Döring ,
T. Riedl ,
T. Rabe  and
W. Kowalsky
S. Döring*
Affiliation:
Institut für Hochfrequenztechnik, Technische Universität Braunschweig, Schleinitzstr. 22, 38106 Braunschweig, Germany
T. Riedl
Affiliation:
Bergische Universität Wuppertal, Lehrstuhl für Elektronische Bauelemente, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
T. Rabe
Affiliation:
Institut für Hochfrequenztechnik, Technische Universität Braunschweig, Schleinitzstr. 22, 38106 Braunschweig, Germany
W. Kowalsky
Affiliation:
Institut für Hochfrequenztechnik, Technische Universität Braunschweig, Schleinitzstr. 22, 38106 Braunschweig, Germany
*
*Email: sebastian.doering@ihf.tu-bs.de
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Abstract

The formation of triplet excitons in semiconducting organic materials plays an important role for the operation of organic optoelectronic devices. Triplet excitons are difficult to investigate spectroscopically at room temperature due to their non-radiative character. Here we show the measurement of the triplet decay dynamics by a highly sensitive time-resolved measurement of the triplet state absorption using pump and probe experiments within a waveguide configuration. Pump and probe pulse have to be separated spatially and in time to ensure a segregation of singlet and triplet excitons. The non-radiative triplet excitons are detected at room temperature by their absorption. A variation of the time delay between pump and probe pulse allows for the investigation of the dynamics of the excitons. Former experiments made use of the photoluminescence of the material under investigation itself as source of probe light. But since there is a spectral shift between the photoluminescence band and the triplet absorption band the spectral bandwidth of probe light has to be broadened for the identification of the triplet absorption. Here we show how a widening of the probe light band up to red part of the spectrum is achieved by an application of extra emission layers. With the help of this technique the triplet exciton dynamics of the hole transport material 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene (SpiroTAD) was measured and analyzed.

Keywords

luminescenceoptical propertiesabsorption
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1629: Symposium N – Functional Aspects of Luminescent and Photoactive Organic and Soft Materials , 2014 , mrsf13-1629-n07-06
Copyright
Copyright © Materials Research Society 2014 

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References

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