Effects of hydrogen plasma treatment on minority carrier diffusion length and recombination velocity at grain boundaries in polycrystalline silicon solar cells have been evaluated by the scanned laser-beam-induced current technique. We have successfully evaluated the two-dimensional minority carrier diffusion length. On the basis of the evaluated diffusion length, the recombination velocity at the grain boundaries was obtained. The recombination velocity was improved by the hydrogen plasma treatment from 15,000-20,000 to 5000-10,000 cm/s. It was quantitatively confirmed that the hydrogen plasma treatment is very effective in both grains and grain boundaries. (c) 2006 Elsevier B.V. All rights reserved.