Damp‐heat degradation and repair of oxide‐passivated silicon

SiO 2 ‐passivated Si degrades when exposed to a ‘damp‐heat’ atmosphere of 85% relative humidity and 85 °C. We find the effective surface recombination velocity at the SiO 2 /Si interface of phosphorus‐diffused (111) Si to increase from 2200 to 11 000 cm/s after 7 days of damp‐heat exposure. This degradation is of concern to many high‐efficiency solar cells, which are manufactured from SiO 2 ‐passivated Si with phosphorus‐diffused (111) facets at the front surface, and which must withstand 1000 h of damp‐heat exposure during reliability testing. Our experiments indicate that the damp‐heat exposure causes (i) absorption of H 2 O into the SiO 2 , (ii) an increase in the concentration of H at the SiO 2 /Si interface, (iii) a latent source of degradation that continues after samples are returned to room conditions, and (iv) SiO 2 /Si interface damage that can be repaired by a short anneal at 300 °C in N 2 . The results of these experiments are discussed in relation to the various mechanisms that might underlie damp‐heat degradation of SiO 2 /Si interfaces.