Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Organic Electronics and Photovoltaics - Layer Morphology and Molecular Aggregation

CPP 3.2: Talk

Monday, March 12, 2018, 10:00–10:15, C 243

The impact of morphology and polymer-fullerene miscibility on device stability of organic solar cells — •Andrej Classen, Chaohong Zhang, Yakun He, Heumueller Thomas, Ning Li, Jose Dario Perea, Stefan Langner, and Christoph Brabec — FAU Erlangen-Nürnberg, Germany, Erlangen

As organic PV efficiencies regularly exceed 10%, the science of stabilization and lifetime gains importance. Several degradation phenomena in organic solar cells are related to an increase in trap density, and have been studied with respect to their impact on open-circuit voltage and fill factor. The short circuit current may be affected by fullerene dimerization which shows a clear dependence on active layer morphology and can be avoided by using different fullerene derivatives. Interestingly, in several novel high performing polymers, such as PTB7 and PCE11, intrinsic morphological instabilities have been observed. Utilizing different fullerene derivatives, we find that increased solubility of the fullerene within the polymer matrix allows superior device stability, but can reduce the initial device performance. Thus a fine balance between stability and device performance has to be found by tuning the donor-acceptor ratio in those systems. To separate effects from several different degradation mechanisms that usually occur at the same time, we perform tests under controlled environmental conditions to avoid photo-oxidation and distinguish between thermal and light induced degradation by applying a series of temperature steps in the dark.