A Novel Origin of Avalanche Breakdown in Multicrystalline Silicon Solar Cells

27th European Photovoltaic Solar Energy Conference and Exhibition; 857-860
The root causes of breakdown of multicrystalline silicon solar cell well below the theoretical limit are investigated in this contribution. The main focus of this paper is on avalanche, or so called type-3, breakdown sites in alkaline texturized solar cells. However, the similarities and differences of the same breakdown type in isotextured solar cells are described as well. Using EBIC charge collecting contrast of p-n junctions at FIB prepared cross sections it is found that possible enhanced phosphorous diffusion at certain line defects in the material leads to spikes of the p-n junction despite of a flat surface of alkaline textured solar cells. Avalanche breakdown occurs at these spikes similar to the avalanche breakdown at etch pits in isotextured solar cells, but at slightly higher absolute reverse voltages as compared to the latter ones. It is assumed that the differences of the breakdown onset voltages are due to the slightly different p-n junction curvature shapes in alkaline and isotextured solar cells.