In this work the impact of hydrogenation from hydrogen-rich amorphous silicon nitride (a-SiNx:H) on dislocations and grain boundaries in multi-crystalline silicon (mc-Si) solar cells is presented. Layers are deposited by means of plasma enhanced chemical vapor deposition (PECVD). Electrical bulk passivation is provided during thermal annealing, in which hydrogen diffuses from a-SiNx:H. The passivation effect is discussed in terms of recombination centers and non-recombinative charge traps reduction as well as in terms of local short circuit current improvement in specially manufactured solar cells.