Laser joining of charge-collection tapes onto CIGS photovoltaics modules

Abstract

Charge-collection tapes (busbar) are an essential component in thin-film photovoltaics (PV) to discharge the current from the solar cell and module. Several application methods have been analyzed so far but there is still need for high-speed processes. While lasers are already used in many processing steps, joining busbars to solar cell is almost not investigated to date. Yet, it appears to be a very promising process especially regarding its potential of cost reduction.The possibility of joining commercially available tinned copper busbars to CIGS solar cells as well as joining two busbars for module interconnection is examined using a pulsed Nd:YAG laser system. Spot joins are carried out using different pulse length, laser power and temporal pulse shapes. Metallurgical cross sectioning is applied in order to discuss reliability issues.Charge-collection tapes (busbar) are an essential component in thin-film photovoltaics (PV) to discharge the current from the solar cell and module. Several application methods have been analyzed so far but there is still need for high-speed processes. While lasers are already used in many processing steps, joining busbars to solar cell is almost not investigated to date. Yet, it appears to be a very promising process especially regarding its potential of cost reduction.The possibility of joining commercially available tinned copper busbars to CIGS solar cells as well as joining two busbars for module interconnection is examined using a pulsed Nd:YAG laser system. Spot joins are carried out using different pulse length, laser power and temporal pulse shapes. Metallurgical cross sectioning is applied in order to discuss reliability issues.