Illumination and Temperature Dependence of Breakdown Mechanisms in Multi-crystalline Silicon Solar Cells

If a solar cell is partially shaded in a photovoltaic module, it can be reverse-biased and therefore dissipate power rather than generating it. When being locally concentrated, this power dissipation can lead to hot spots damaging solar modules irreversibly. In order to assess the hot spot danger of solar cells prior to module integration, their operating points under partial shading conditions need to be known which can be determined by simulation. We show, that deviations between simulated and measured module I-V characteristics can be explained by contrary temperature- and illumination-dependent effects on the reverse characteristic of a multi-crystalline silicon solar cell. A negative temperature coefficient for voltages of V < -12.5 V in the temperature range of T = 25-50 °C is determined to be mainly due to type II and III breakdown while a positive illumination coefficient is found for V < -6 V which predominantly originates from locally distributed currents.