Electric field‐enhanced degradation has been observed in amorphous silicon solar cells exposed to intense illumination (45–60 suns) at elevated temperatures (≳160 °C). The front tin oxide contacts of bothp–i–nandn–i–pcells darken significantly when a strong reverse bias is applied at elevated temperatures and under intense illumination. Compositional profiles of the cells show that a strong reverse bias causes a depletion of hydrogen near the contacts. These results are interpreted in terms of proton motion near thep/iinterface ofp–i–ncells and negative hydrogen ion motion near thei/ninterface. ©1996 American Institute of Physics.