Effects of spot size variation on the laser induced breakdown spectroscopy analysis of Cu(In,Ga)Se2 solar cell

The effects of spot size variation on the results of laser induced breakdown spectroscopy (LIBS) analysis of Cu(In,Ga)Se2 (CIGS) thin film solar cell using a scanning laser beam (λ = 532 nm, τ = 5 ns, top-hat spatial profile) are reported. The spot diameter of laser beam was reduced from 150 μm to 35 μm, below the laser P2 scribing pattern width, at the fixed laser fluence of about 4.5 J/cm2 and overlap ratio of 79%. The results showed that the measured LIBS signal intensity ratio rather than intensity could be nearly independent of laser spot diameter if the spectral lines are properly selected. It is demonstrated that the concentration ratio of CIGS layer can be predicted within 5% error from the average concentration ratio measured by inductively coupled plasma optical emission spectroscopy by LIBS analysis with a spot diameter of 50 μm.