Regensburg 2004 – scientific programme

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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 5: Poster

SYOH 5.50: Poster

Thursday, March 11, 2004, 18:00–21:00, B

High efficiency charge carrier generation and recombination free charge carrier transport in polymer-fullerene bulk heterojunction devices — •Vladimir Dyakonov¹, Ingo Riedel¹, Pavel Schilinsky^1,2, Christoph Waldauf^1,2, and Christoph Brabec² — ¹Energy- and Semiconductor Research Laboratory, Institute of Physics, University of Oldenburg, D-26111 Oldenburg, Germany — ²Siemens AG, Innovative Electronics,CTMM1-L₂P, Paul-Gossen-Strasse 100, D-91052 Erlangen, Germany

We present experimental evidences for the efficient photogeneration of charge carriers in photovoltaic conjugated polymer-fullerene blends followed by the recombination-free charge carrier transport through the semiconductor layer. From the incident photon conversion efficiency exceeding 70%, an internal quantum efficiency of close to 100% was calculated, indicating high potential of these materials for solar cell applications. We demonstrate that by increasing the active layer thickness (up to 350 nm) without significant decrease of internal quantum efficiency, high short-circuit photocurrent densities (J_SC) of 15 mA/cm² can be achieved. The temperature dependence of the photocurrent generally reflects the charge carrier transport losses in the device under test. Being thermally activated at low temperatures, the J_SC saturates and becomes nearly temperature independent above T=260 K, indicating that the charge carriers traverse the active layer without being influenced by the semiconductor’s transport properties. The corresponding high value of the mobility-lifetime product µτ provides therefore a basis to design solar cells with thick absorber layers able to overcome transport limitations.