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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Organic Semiconductors

CPP 8.46: Poster

Montag, 14. März 2011, 17:30–19:30, P2

Near Infrared Spectroscopic Studies of Boundary Effects on n-doped Organic Semiconductor Layers — •André Merten, Moritz Riede, and Karl Leo — IAPP/TU-Dresden, George-Bähr-Straße 1,01069 Dresden

Doping of organic semiconductors is a useful method to achieve well selected charge carrier transport properties and alignment of electronic energy levels. The efficacious p-i-n concept for small molecule organic light emitting diodes or solar cells is based on the doping of the electron- and the hole-transport layers in which the active layer is embedded. Besides providing appropriate conductivity, the doping reduces injection or extraction barriers between the organic layers or organic layers and the contacts, respectively, by adjusting energetic levels. Highly doped organic layers are also used as very efficient conversion contact in organic tandem solar cells.In this study we focus on the near infrared absorption properties of n-doped organic layers on ITO or in organic layers stack like solar cells. We found a considerable elevated near infrared absorptance if the n-doped organic materials were evaporated directly on ITO, which is in contradiction to the optical constants of the ITO and of the doped materials which were determined on glass substrate. This effect will allow an inside on the elevated charge carrier concentration and the shape of the energetic bands on the organic layer-ITO boundary. As example for the consequence of this effect on small molecule organic solar cells, the IV and spectral response characteristics of device in the inverted p-i-n design, using n-C60 as ETL is discussed.