Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 5: Photovoltaics: CIGS and related compounds

HL 5.1: Talk

Monday, March 16, 2015, 09:30–09:45, EW 202

Investigation of Defect Levels in Al/Cu(In,Ga)Se₂ Schottky Contacts and ZnO:Al/CdS/Cu(In,Ga)Se₂ Heterojunctions via Temperature-Dependent Admittance Spectroscopy — •Sara L. Gadeberg, Maria S. Hammer, and Ingo Riedel — Energy and Semiconductor Research Laboratory, Chair: Jürgen Parisi, Department of Physics, University of Oldenburg

Regardless their broad application and investigation, many properties of the Cu(In,Ga)Se₂ compound semiconductors (CIGSe) have still not been sufficiently explained. For instance, the nature of certain defect signatures (interface or bulk) is still under discussion. In this study different Schottky contacts (Al/CIGSe/MoSe₂/Mo) were prepared from CIGSe solar cells (ZnO:Al/CdS /CIGSe/MoSe₂/Mo) via etching removal of the ZnO:Al/CdS window layer, surface treatment of the remaining CIGSe layer, and subsequent metal deposition. In order to differentiate between bulk and heterojunction interface defects, we recorded temperature-dependent admittance spectra (TAS) (T=30 - 310 K). The TAS data were evaluated in two ways: i) by applying the common method using the derivative of the capacitance and ii) by direct analysis of the phase shift of the impedance, which does not require particular assumptions on the electrical device equivalent circuit. The defect signatures found in the Schottky devices were compared to those found in the original CIGSe solar cells. Based on our results we will discuss the spatial origin of the different defect levels and comment on the reliability of the direct evaluation method for TAS data as proposed in this work.