Weldability of GaAs solar cells on either GaAs or Ge substrates

A three-dimensional, time-dependent model is developed for parallel gap welding of GaAs/GaAs and GaAs/Ge solar cells. Both GaAs/GaAs and GaAs/Ge solar cells have been welded successfully. However, variations in welding conditions can lead to defects that affect the electrical performance or the reliability of cells interconnected into arrays. In many cases, the main defects are small cracks. The results of the modeling show that cracks can be caused by insufficient dissipation of the heat generated by the welding current. The model also shows that welding cracks can be reduced by changing the welding parameters (reducing weld energy, decreasing the size of the welded region between the probe contact areas). When the calculated welding procedures were implemented, acceptable welds were obtained.