Microanalysis of laser micro-welded interconnections in CIGS PV modules

Laser micro-welding is a technique that can be used for interconnective (P2) patterning of Cu ( In , Ga ) Se 2 (CIGS) thin film solar cells after deposition of the ZnO:Al window layer. The micro-welding process transforms CIGS into a conductive compound that forms a contact between the ZnO:Al front contact and the Mo back contact. In this work we present a study on the influence of process parameters on the interconnectivity of the laser micro-weld as well as an investigation of the morphology of the micro-weld zone. We found that the current method results in an overlap of conditions where electrical connection is achieved and where Mo/glass damage is caused by laser action. Stability testing shows that interconnections processed without appreciable damage are stable. The connecting region contained metal rich zones and segregated CuxSe that we believe account for its conductivity.