Evaluating root cause : the distinct roles of hydrogen and firing in activating light- and elevated-temperature induced degradation

Abstract

The root cause of light- and elevated temperature-induced degradation (LeTID) in multicrystalline silicon p-type passivated emitter and rear cell (PERC) devices is still unknown. In this contribution, the bulk hydrogen concentration is varied using microwave-induced remote hydrogen plasma (MIRHP). This technique allows us to separate the effects of hydrogen and firing temperature in LeTID-affected wafers. We find that hydrogen is required for degradation to occur, and that samples fired prior to the introduction of hydrogen do not degrade. We conclude that firing is not required to cause LeTID. Together, these observations suggest that hydrogen, rather than metal-rich precipitates that dissolve during firing, for example, plays a determining role in LeTID.