Study of Solar Cells by Sem Dark Voltage Contrast

For the first time the Scanning Electron Microscopy (SEM) Dark Voltage Contrast (DVC) technique was used to examine the field distribution in a solar cell made of polycrystalline silicon. The samples were cut off solar cells made of Edge-defined Film-fed Grown (EFG) Silicon and lapped at 2 and 5 degree angles. The DVC measurements were performed at forward, reverse, and zero bias conditions using a Hitachi S-570 SEM and a Kevex-8000 microanalyzer. The I-V curves were recorded to test the electric performance of the samples. We examined two groups of solar cells. One group of cells demonstrated, after regular processing, reasonable electrical performance and abrupt DVC profile. The other group was intentionally doped with titanium, which presumably was agglomerated in the p-n junction area thus degrading completely the electrical performance of the cells and weakening the electric field by a factor of 4–6.