A microanalytical study of aluminium diffusion in photovoltaic cells usingimaging-mode laser-induced breakdown spectrometry

Diffusion of aluminium in solar cell fingers into the silicon bulk has been studied using imaging-mode laser-induced breakdown spectrometry (LIBS). Th e focused beam of a pulsed N-2 laser (337.1 nm) was used to create a microp lasma on the target surface. Due to the beam profile of the nitrogen laser, the resulting crater had an elliptical shape, Subsequent plasma optical em ission of the plasma was spectrally and spatially resolved and detected wit h a non-intensified charged-coupled device detector. A total area of 3 x 2. 5 mm(2) has been sampled with a lateral resolution of 50 mu m in the minor direction axis of the elliptical crater. Chemical maps of aluminium and sil ver are shown. Depth maps of aluminium diffusion for different lateral posi tions in the sample have been obtained. The capability to distinguish betwe en the diffused aluminium and that belonging to solar cell fingers is demon strated by using a simple mathematical algorithm in the post-processing of the spatially resolved spectral data. The results show the capabilities of LIES to provide rapid and simultaneous multielemental chemical imaging of s ilicon materials. (C) 2000 Elsevier Science B.V. All rights reserved.