Images of grain boundaries in polycrystalline silicon solar cells by electron and ion beam induced charge collection

Selected grain boundaries in a polycrystalline solar cell have been imaged by the electron beam induced current (EBIC) technique of the scanning electron micro-scope and the ion beam induced charge (IBIC) method, using a 2.0 MeV focused He+ ion beam. The IBIC maps show lower resolution and weaker contrast in comparison to EBIC images, as a result of the larger spot size of the ion beam. However, IBIC allows an analysis of the height of the charge pulses produced by single ions; examples of the spectra thus obtained at different regions of the cell are given, and the relation between spectrum shape and local charge collection properties of the specimen is briefly discussed.