Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Photovoltaics: mainly Technology and Photon Management

HL 55.11: Talk

Wednesday, March 16, 2011, 17:15–17:30, FOE Anorg

Picosecond Excited State Spectroscopy of Organic Bulk Heterojunctions — •Björn Gieseking¹, Berthold Jäck¹, Carsten Deibel¹, and Vladimir Dyakonov^1,2 — ¹11Experimental Physics VI, Faculty of Physics and Astronomy, Julius- Maximilians-University Würzburg, D-97074 Würzburg — ²2Bavarian Centre for Applied Energy Research (ZAE Bayern), D-97074 Würzburg

Bulk heterojunction solar cells comprised of conjugated polymers and fullerene derivatives approach efficiencies of 8 % making this composite system a promising candidate for the application in organic photovoltaics. Different approaches for improving the device performance aim at the physical properties of the material system itself, but a further optimization requires a deeper insight into the elementary processes following the photoexcitation of these blends.

Here we present recent time-resolved spectroscopic studies on the conjugated Polymer P3HT blended with different fullerene derivatives employing femtosecond transient absorption (TA) and photoluminescence (PL) spectroscopy. For both methods we use an Ti:sapphire-based femtosecond laser system together with two optical parametric amplifiers and a streak camera providing a time resolution in the sub picosecond (TA) and picosecond (PL) regime, respectively. Applying these techniques we studied the recombination dynamics of singlet excitons and polarons after photoexcitation. We will discuss our results in terms of performance optimisation of organic solar cells.