Hot spotting and second breakdown effects on reverse I-V characteristics for mono-crystalline Si photovoltaics

Abstract

Hot spots are a common problem in photovoltaic (PV) panels that accelerate cell degradation and reduce system performance. Hot spots occur when a cell is reversed biased, sinks power, and heats the cell. At a certain threshold, the PV p-n junction goes into second breakdown and heats a small portion of the cell to very high temperatures. This study experimentally tests mono-crystalline Si cells as they hot spot at different power levels. Heating effects on the I-V characteristics during hot spotting and permanent changes after seven days of hour-long hot spot tests are observed and analyzed. I-V characteristics are significantly affected under second breakdown, which is observed when cells are reverse-biased above two times the rated maximum power level.