Identification of pre-breakdown mechanism of silicon solar cells at low reverse voltages

The local breakdown of commercial silicon solar cells occurring at reverse voltages of only 3-4 V has been investigated by means of current-voltage measurements, dark lock-in thermography, and reverse-biased electroluminescence (ReBEL) with a spatial resolution on the micrometer-scale. It is shown that the origin of the local breakdown (so-called type I) can be traced back to a contamination of the wafer surface with Al particles prior to the phosphorous diffusion step. A model is presented explaining that the spectral maximum of ReBEL is within the visible range.