You are here: Home Eva-Mayr-Stihl Chair … Research High-efficiency In-free thin-film …

Content

Widening the band gap of Cu(In,Ga)Se2 (CIGS) absorber layer has a big advantage not only for the single junction CIGS solar cells, but also for tandem devices where CIGS can be used as a top cell. This can be realized by either increasing the Ga content in the absorber layer to almost 100 at.% (In-free absorber layer) or by included Ag as a matrix element. Obtaining In-free absorber layer is of big relevance for obtaining green sustainable devices and materials, solving the problem of In-scarcity in nature.

However, the functional properties of the newly In-free absorber layer have to be further improved to meet the requirements for a high-performance solar cell. Hence, Re-Design of absorber layers with superior functional properties can be done through two directions that the CMC group is working on:

  1. Controlled growth by magnetron sputtering of absorbers layer with new functionalities.
  2. Nanocharacterization down to the atomic level using atom probe tomography and correlative microscopy.   

For example, below is an example of In-free CuGaSe2 (CGS) absorber layer investigated by atom probe tomography. The 3D reconstruction map given on the left provides the redistribution of Cu as a matrix element, but also of Na and Rb as light and heavy alkali. This study clearly reveals two important information:

  • The formation of CuGa3Se5 OVC (ordered vacancy compound) inside the absorber layer;
  • The redistribution of Na light alkali distinguishes neatly from that of the Rb heavy alkali: Na is mainly accumulated in the OVC compound, while Rb is found mainly accumulated at the interfaces.

Bild2.jpg