Low-temperature dark anneal as pre-treatment for LeTID in multicrystalline silicon

Light and elevated temperature induced degradation (LeTID) is currently a severe issue in crystalline silicon photovoltaics, which has led to numerous efforts to both understand the mechanism and to mitigate it. Here we show that a low-temperature dark anneal performed as the last step in typical solar cell processing influences greatly LeTID characteristics, both the strength of the degradation and the degradation kinetics. While a relatively short anneal in the temperature range of 200–240 °C can be detrimental to LeTID by doubling the degradation intensity, an optimized anneal at 300 °C shows the opposite trend providing an efficient means to eliminate LeTID. Furthermore, we show that the simulated recombination activity of metal precipitation and dissolution during the dark anneal correlates with the experiments, suggesting a possible explanation for the LeTID mechanism.