Improvement of selenium analysis during laser-induced breakdown spectroscopy measurement of CuIn1−xGaxSe2 solar cell films by self-absorption corrected normalization

Abstract

The analysis of Se emission lines (196.089 nm and 203.984 nm) of CuIn_1−xGa_xSe₂ (CIGS) thin solar cell films by laser-induced breakdown spectroscopy (LIBS) is reported. With CIGS thin films fabricated by co-evaporation or sputtering methods, LIBS measurement was carried out using a nanosecond laser (λ = 532 nm, τ = 5 ns, top-hat profile) and a CCD spectrometer (gate width = 1.05 ms, gate delay = 0.2 μs) in a flowing Ar gas environment (20 L min⁻¹). From the comparison of calibration curves, it was found that the correlation between the Se/Cu LIBS intensity ratio and the Se/Cu concentration ratio could be improved significantly by applying the self-absorption correction procedure introduced in this study, demonstrating the significance of self-absorption in those Se emission lines. It was shown that normalization alone could reduce the relative standard deviation but was insufficient for accurate LIBS analysis of Se in CIGS thin films.