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Graded absorption layers in bulk heterojunction organic solar cells

: Beyer, B.; Pfeifer, R.; Zettler, J.K.; Hild, O.R.; Leo, K.


Journal of physical chemistry. C, Nanomaterials and interfaces 117 (2013), No.19, pp.9537-9542
ISSN: 1932-7447
ISSN: 1932-7455
Journal Article
Fraunhofer COMEDD; 2015 ()

Bulk heterojunction organic solar cells with a vertical variation of the C60:ZnPc composition within the absorption layer have been fabricated. The resulting gradient layer has been characterized by UV/vis transmission and reflection spectroscopy. Depending on the mixing strategy, the formation of higher aggregated ZnPc species can be initialized earlier in a blended thin film. The gradient strength has been varied and its influence on the solar cell performance has been determined. A variation of the absorption layer thickness has been carried out to investigate a possible charge carrier transportation improvement. In order to explain the positive effect of a graded structure within the absorption layer, detailed voltage-dependent spectral response measurements have been performed. It is shown that not only the absorption behavior of the cell is improved, but also the charge carrier transportation properties.