Hot spots and heavily dislocated regions in multicrystalline silicon cells

The formation mechanism and the electrical consequences of hot spots have been investigated in multicrystalline solar cells. The hot spots were revealed by means of an infrared camera when the cells are reverse biased in the dark. The minority carrier diffusion length (L _n), the photovoltage (V_oc), and the photocurrent (J_sc) were measured in the hot-spot area and far from this zone with the aid of mesa diodes. Dark forward I-V curves lead to values of ideality factor (M) and reverse saturation current (J_o). It is found that J_o and M are higher in the hot-spot area, while J_sc, V_oc, and, to a lesser extent. L_n are smaller. Large densities of dislocations and lineage structures are revealed in the abnormally heated regions