Regensburg 2013 – scientific programme

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DS: Fachverband Dünne Schichten

DS 23: Focus Session: Thin Film Photovoltaic Materials and Solar Cells II

DS 23.10: Talk

Wednesday, March 13, 2013, 17:15–17:30, H8

Device analysis of CIGSe superstrate solar cells — •Marc D. Heinemann, Christian A. Kaufmann, Britta Höpfner, Thomas Unold, and Hans-Werner Schock — Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany

Cu(In,Ga)Se2 solar cells in the superstrate configuration offers a number of advantages regarding industrial device fabrication as well as the option of direct application in tandem device structures. The drawback is the lower efficiency due to the difficulty to design the heterointerface, which traditionally relies on buffer layers like CdS that are unstable at the high process temperatures. In this work superstrate Cu(In,Ga)Se2 solar cells are prepared by coevaporation at different temperatures directly on a variety of ZnO coated glass substrates. Depending on the process conditions, the formation of a thin GaO compound or InO compound layer has been observed at the interface. It was found that the InO layer enables the Zn diffusion into the absorber and induces a low shunt resistance, whereas the GaO layer acts as a diffusion barrier for Zn. Currently a max conversion efficiency of around 7% has been achieved. The device performance of these superstrate devices is modeled by numerical simulation, taking into account results from admittance and photoelectron spectroscopy of the interface. To overcome the efficiency limiting effects derived from this device model, different interface conditionings in combination with the application of a variety of buffer layers are carried out and will be presented.