Raman Microspectroscopy of a Multi-Crystalline Silicon Solar Cell

A multicrystalline silicon solar cell was analyzed using Raman microspectroscopy. We measured the prominent Raman modes of silicon, nanocrystalline silicon and silver oxide in various regions of the solar cell to generate insights into the process and material quality of the finished device. First, by comparing the distribution of the transverse optical (TO) phonon peak position and full-width-at-half-maximum (FWHM) of the solar cell with a single crystal silicon wafer, the quality of the multicrystalline silicon surface was ascertained. Second, a similar analysis of the remnant saw marks on the device surface showed a discernably higher and wider distribution of TO phonon peak position and FWHM compared to a multicrystalline silicon surface. This indicated the presence of residual compressive stresses in the saw mark region. Third, by observing the silver fingers and bus bars, a residual silver oxide layer was identified, up to 25 μm away from the line edges. This was attributed to the screen printing of the silver paste and the subsequent firing process. Finally, Raman mapping on an embedded inclusion showed the presence of nanocrystalline silicon phase. The multicrystalline silicon region surrounding the inclusion was under tensile stress. A nondestructive, confocal Raman analysis of the inclusion provided a 3-D visualization of the defect, both inside and above the surface of the multicrystalline silicon wafer.