Na distribution in Cu(In,Ga)Se2 thin films: Investigation by atom probe tomography

  Atom probe tomography (APT) has been used to study the distribution of Na atoms in polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films. APT, which allows separate investigations of grain boundaries and grain interiors chemistry, shows the presence of inter- and intra-granular Na segregations. It is highlighted that these segregations are found associated to Cu-depletion and In-enrichment. The segregation of Na to crystalline point defects and extended ones is finally discussed regarding its impact on the electrical properties of CIGSe layers.