Berlin 2012 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 44: Poster IV: Thin film photovoltaics; Organic electronics and photovoltaics (jointly with CPP, HL, O); Organic thin films; Trends in atomic layer deposition (Focused session)

DS 44.4: Poster

Freitag, 30. März 2012, 09:30–12:00, Poster E

Photovoltaic energy conversion based on strongly correlated oxides — •Benedikt Ifland¹, Gesine Saucke², Jonas Norpoth¹, Jörg Hoffmann¹, and Christian Jooss¹ — ¹Institute of Materials Physics, University of Göttingen, Germany — ²Institute for Condensed Matter Physics, University of Zürich, Switzerland

Materials with strong electron-electron or electron-phonon interaction offer promising opportunities in search for new fundamental mechanisms of light harvesting in solar cells via tuning their correlation interactions. We have studied two types of manganite-titanite pn-heterostructures, where p-doped manganites are deposited on single crystal substrate of n-type SrTi_1−xNb_xO₃ (STNO) via ion beam sputter deposition: Pr_1−xCa_xMnO₃ (PCMO) shows semiconducting behavior based on thermally assisted hopping of small polarons. In contrast, La_1−xSr_xMnO₃ (LSMO) exhibits band like "metallic" conductivity and ferromagnetic order. It may form a Schottky like junction in electrical contact with STNO. Current-voltage-characteristics of the oxide junction in a temperature range between 25 and 300 K show strongly rectifying behavior. Although both p-type manganites have no optical band gap at 300K, the junctions reveal a photovoltaic effect. The open circuit voltage increases with decreasing temperature up to several hundred millivolts. Experimental results are discussed with respect to conventional semiconductor models, taken also into account the non-linear mobility of polarons in the presence of an electric field.