Dresden 2009 – scientific programme
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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices
SYOP 4: Organic Photovoltaics: from Single Molecules to Devices
SYOP 4.38: Poster
Thursday, March 26, 2009, 16:30–19:00, P1A
Investigation of s–shaped current–voltage characteristics of organic bulk heterojunction solar cells — •Daniel Rauh1, Stefan Geißendörfer1, Carsten Deibel2, and Vladimir Dyakonov1,2 — 1Bavarian Centre for Applied Energy Research e.V. (ZAE Bayern), D-97074 Würzburg — 2Julius-Maximilians-University of Würzburg, Institute of Physics, Experimental Physics VI, D-97074 Würzburg
In order to achieve a high performance in organic solar cells, reaching a reproducibly high fill factor – the solar cell parameter which depends on internal device structure and electrodes mostly sensitive – is crucial. Depending on the preparation conditions, sometimes the problem of s–shaped current–voltage (IV) curves arises, causing a low fill factor and therefore a low power conversion efficiency. In order to investigate this double diode behaviour, we prepared poly(3-hexyl thiophene):methanofullerene bulk heterojunction solar cells with a blend ratio of 1:1, varying the processing conditions. We discovered two different types of s–shapes, one with an increasing slope after the inflexion point and the other with a decreasing slope. We discuss space charged limited currents, trap states and internal energy barriers as as potential origin of the double diode behaviour.