Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 40: [CPP] Organic Electronics and Photovoltaics II (Joint Session DS/CPP/HL/O)

O 40.1: Talk

Tuesday, March 23, 2010, 13:45–14:00, H37

Spectroscopic signatures of C₇₀-Anions in Polymer-Fullerene composites — •Andreas Sperlich¹, Moritz Liedtke², Hannes Kraus¹, Oleg Poluektov⁴, Carsten Deibel¹, Nazario Martin³, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Würzburg, D-97074 Würzburg — ²ZAE Bayern, Div. Functional Materials for Energy Technology, D-97074 Würzburg — ³Departamento de Quimica Organica, Facultad de Quimica, Universidad Complutense, E-28040 Madrid — ⁴Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700, USA

C₇₀-derivates are used in the most efficient organic bulk heterojunction solar cells. However, the detailed photophysical processes in composites containing C₇₀ are still unresolved. In this contribution, our focus is on the light-induced charge transfer from the polymer to the fullerene, generating negatively charged C₇₀ radicals. Photoinduced absorption (PIA), electron spin resonance (ESR 9.5GHz) and optically detected magnetic resonance (ODMR) were used to draw a picture of the photoinduced charge transfer from polymers to C₇₀. We provide the first experimental identification of the light induced C₇₀ radical anion in blends with P3HT using high frequency ESR (130GHz). Comparing spectra from C₇₀-derivates with different sidechains, we could confirm that the electron is indeed localized on the C₇₀-cage. Further, we identify an additional absorption band at 0.9eV due to C₇₀⁻ by PIA.