The effect of high pressure pure hydrogen annealing (HPHA) on the conversion efficiency of multicrystalline silicon solar cells was investigated at various temperatures and pressures. HPHA led to a better supply of hydrogen near the interface between the Ag electrode and the SiN antireflection layer of a solar cell, resulting in increased cell conversion efficiency. As compared with an as-fabricated sample, the postannealed samples in pure hydrogen ambient under optimum process conditions exhibited the improved cell conversion efficiency by 2% absolute. HPHA is a useful method to enhance the conversion efficiency of low grade multicrystalline silicon solar cells. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3485082] All rights reserved.