Exploring the p-n junction region in Cu(In,Ga)Se2 thin-film solar cells at the nanometer-scale

In this work we study the CdS/Cu(In,Ga)Se-2 p-n junction region in Cu(In,Ga)Se-2 thin-film solar cells using atom probe tomography. A Cu-, Ga-depleted, and Cd-doped region of about 1 nm thickness is detected at the Cu(In,Ga)Se-2 side of the CdS/Cu(In,Ga)Se-2 interface. Furthermore, Cd is also found to be enriched at Cu(In,Ga)Se-2 grain boundaries connected to the CdS layer. Na and O impurities decorate the CdS/CIGS interface, where Na-rich clusters are preferentially located in CdS regions abutting to Cu(In,Ga)Se-2 grain boundaries. The experimental findings of this work demonstrate the capability of atom probe tomography in studying buried interfaces and yield vital information for understanding and modeling the p-n junction band structure in Cu(In,Ga)Se-2 solar cells. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764527]