Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 112: Energy materials: CIGS and related photovoltaics

HL 112.8: Vortrag

Freitag, 4. April 2014, 11:30–11:45, POT 112

Investigation of contact barriers of co-evaporated Cu(In,Ga)Se₂ and Molybdenum — •Nils Neugebohrn, Maria S. Hammer, Jürgen Parisi, and Ingo Riedel — Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, 26111 Oldenburg, Germany

Cu(In,Ga)Se₂ (CIGSe) solar cells have recently reached a record efficiency of 20,8%. Nevertheless, the electronic properties of the back contact which forms between CIGSe and molybdenum are poorly understood. For this interface Schottky-type as well as ohmic behavior has been reported previously. In particular, the intermediate MoSe₂ layer which forms between the absorber and the metal during growth of the CIGSe layer determines the contact characteristics and might be critical for the device performance. The energy band alignment at the CIGSe/MoSe₂/Mo interfaces depends on the growth conditions and material properties (absorber composition, Na-content of the absorber and Mo). In this study Au/CIGSe/MoSe₂/Mo samples have been prepared via etching of the ZnO/CdS window layer of the complete cell and subsequent deposition of Au contacts on top of the CIGSe layer. To study a potential barrier-induced current limitation we performed temperature-dependent current-voltage measurements between 80 and 300 K. We observed an exponential dependence of the injection current indicating the presence of a contact barrier. The barrier height is determined by employing the thermionic emission model. Based on these results we will discuss the location of this barrier, e.g. at the CIGSe/MoSe2 or at the MoSe₂/Mo interfaces.