SPLTRAK Abstract Submission
Determining the decomposition voltage of Cu(In1-xGax)Se2
Klaas Bakker1,4, Joaquin Coll Matas1, Johan Bosman1, Nicolas Barreau2, Arthur Weeber3,4, Mirjam Theelen1
1TNO partner in Solliance, Eindhoven, Netherlands
/2Université de Nantes, Nantes, France
/3TNO, Petten, Netherlands
/4TU Delft, Delft, Netherlands

CIGS modules can be permanently damaged when partially shaded. This damage is caused by a reverse bias potential over the shaded areas. The affected area contains local shunts that are identified as wormlike defects by their distinct appearance. A lot is already known about these wormlike defects. Previous studies have given insight in the origin and propagation of wormlike defects. Two separate studies have concluded that there is a large influence of the local electric field on the formation and propagation of wormlike defects. The first study was on the influence of the TCO layer on the propagation of wormlike defects. The second study showed that the formation of wormlike defects is a voltage driven process and the influence of the CIGS absorber layer thickness on the formation of wormlike defects. However, in order to predict and prevent wormlike defects, the sensitivity of the CIGS absorber layer towards an electric field needs to be determined. In this study a dedicated test structure was developed to investigate the behavior of the CIGS absorber material used in solar cells, under the influence of an electric field. It was found that the bare CIGS material decomposes similarly to when wormlike defects are created. The voltage at which this appears was coined the decomposition voltage, and has a correlation with the copper content of the CIGS. We hypothesize that initially the chalcogenide CIGS structure decomposes to the copper poor ordered vacancy compound (OVC) and copper selenide under influence of a large electric field.