Shunt types in crystalline silicon solar cells

Nine different types of shunt have been found in state-of-the-art mono- and multicrystalline solar cells by lock-in thermography and identified by SEM investigation (including EBIC), TEM and EDX. These shunts differ by the type of their I-V characteristics (linear or nonlinear) and by their physical origin. Six shunt types are process-induced, and three are caused by grown-in defects of the material. The most important process-induced shunts are residues of the emitter at the edge of the cells, cracks, recombination sites at the cell edge, Schottky-type shunts below grid lines, scratches, and aluminum particles at the surface. The material-induced shunts are strong recombination sites at grown-in defects (e.g., metal-decorated small-angle grain boundaries), grown-in macroscopic Si3N4 inclusions, and inversion layers caused by microscopic SiC precipitates on grain boundaries crossing the wafer. Copyright (C) 2004 John Wiley Sons, Ltd.