Micro-Raman Mapping of Residual Stresses at Grain Boundaries in Multicrystalline Block Cast Silicon Solar Cell Material: Their Relation to the Grain Boundary Microstructure and Recombination Activity

We study multicrystalline silicon (mc-Si) block cast wafer solar cell material with respect to mechanical residual stresses at grain boundaries (GBs) related to GB type, details of microstructure, and electrical activity of the GBs. For this purpose we combine micro-Raman spectroscopy, electron backscatter diffraction, and electron beam induced current techniques. Stresses of several tens of MPa are found not to influence the electrical activity in block cast mc-Si. Inhomogeneous distributions of residual stresses and electrical activity are observed along the same GB as well as along different GBs of the same type. These results are discussed in terms of local variations in the GB microstructure due to the presence of dislocations superimposed on the GB, their arrangement, intrinsic structure, and impurity decoration.