Electromodulated photoinduced absorption: a new spectroscopy in <pi>-conjugated polymer/C60 blends

Martin Liess; Paul A. Lane; Zakya H. Kafafi; M. Hamaguchi; Masanori Ozaki; Katsumi Yoshino; Z. Valy Vardeny

doi:10.1117/12.293356

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1 November 1997 Electromodulated photoinduced absorption: a new spectroscopy in π-conjugated polymer/C₆₀ blends

Martin Liess, Paul A. Lane, Zakya H. Kafafi, M. Hamaguchi, Masanori Ozaki, Katsumi Yoshino, Z. Valy Vardeny

Author Affiliations +

Proceedings Volume 3142, Fullerenes and Photonics IV; (1997) https://doi.org/10.1117/12.293356
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

We have applied the electromodulated photoinduced absorption (EPA) technique to a variety of C₆₀-doped and pristine luminescent conducting polymer films. EPA measures the electric field-related change of the absorption in the sample as a result of above-gap illumination. An electric field leads to two major effects. One is a possible Stark shift of photoexcitation energy levels, and the other is a change in the photoexcitation decay kinetics, which leads to reduction or enhancement of PA features. This can be due to an electric field enhanced dissociation of the 1Bu exciton or due to a lifetime reduction of polaron pairs. The EPA technique helps to elucidate the photoinduced absorption bands of the charge transfer complex C₆₀^- P⁺, where P⁺ is a positively charged polaron on the polymer chain. The following thin films were studied by EPA: MEH-PPV/C₆₀, pristine MEH-PPV, PPP/C₆₀, P3OT/C₆₀, PTSi/C₆₀, and pristine PTSi. We found for the two PA bands of polarons that E(LE) + E(HE) equals E_g. We also found that the polarizability of polaron pairs in three orders of magnitude bigger that the polarizability of the 1B_u exciton.

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Martin Liess, Paul A. Lane, Zakya H. Kafafi, M. Hamaguchi, Masanori Ozaki, Katsumi Yoshino, and Z. Valy Vardeny "Electromodulated photoinduced absorption: a new spectroscopy in π-conjugated polymer/C₆₀ blends", Proc. SPIE 3142, Fullerenes and Photonics IV, (1 November 1997); https://doi.org/10.1117/12.293356

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