Electrical Properties of Different Types of Grain Boundaries in Multicrystalline Silicon by Photoluminescence Imaging
نویسندگان
چکیده
There are numerous types of Grain Boundaries (GBs) present in multicrystalline silicon wafers, such as ∑3, ∑9, ∑27 and Random Angle (RA) GBs. Small-Angle Grain Boundaries (SA GBs) are also common, and often occur in locally dense networks, creating regions of high recombination. These GBs can limit the efficiency of multicrystalline silicon solar cells, especially when they are decorated with impurities. However, the electrical properties of GBs are not fully understood. Here we examine the recombination activities of different types of GBs by photoluminescence (PL) imaging, combined with Electron Back-Scattered Diffraction (EBSD) data to determine the GB types. We quantify the recombination strength of GBs with two different methods the PL contrast at the GBs, and the GB induced recombination current. Our results indicate that SA GBs are the most recombination active GBs, followed by ∑27 GBs, while the majority of ∑3 and ∑9 GBs are recombination inactive. The influences of injection level, bulk lifetime and surface condition on the recombination strength of GBs are also discussed.
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