Regensburg 2013 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 32: Poster Session IV: Atomic layer deposition; Organic thin films; Organic Electronics and Phototovoltaics; Organic Materials for Spintronics - from spinterface to devices; Thin film photovoltaic materials and solar cells

DS 32.39: Poster

Donnerstag, 14. März 2013, 17:00–20:00, Poster B2

Electronic structure derived from SXPS of TiO2/C60 and AZO/C60 as model electron extraction interfaces in inverted organic solars — •Philip Reckers¹, Sara Trost², Thomas Riedl², Thomas Mayer¹ und Wolfram Jaegermann¹ — ¹Technische Universität Darmstadt — ²Bergische Universität of Wuppertal

We present first results of our study on inverted organic solar cells (IOSC) using synchrotron induced photoelectron spectroscopy (SXPS). A typical device structure is ITO/TiO2/ PCBM:P3HT/MoO3/Ag. The low work-function (LWMO) transparent metal oxide conductors TiO2 or AZO act as electron extraction layer and MoO3, with its high work-function (HWMO) as hole extractor. IV-characteristics using TiO2 show photovoltaically unvafourable s-shape while AZO shows good diode characteristic. As PCBM cannot be evaporated without destruction, we investigate the model interface TiO2/C60 and compare the derived interface band diagram to AZO/C60. The LWMOs were deposited ex-situ via ALD. The acceptor C60 was evaporated stepwise onto the LWMO. Band diagrams for the pristine materials and for the hetero-junctions are derived from SXPS spectra taken at BESSY II. The used energy gaps are derived from UV-Vis absorption spectra. The CBM/LUMO offset for TiO2/C60 is 100 meV, and for AZO/C60 is 300meV with the LUMO above the conduction band maxima. Thus there is no offset at the TiO2/C60 interface that was suspected to cause the unfavourable s-shaped IV-characteristic observed in the IOSC using PCBM.