The electronic transport properties and the microstructure of a series of hydrogenated polymorphous silicon (pm-Si:H) samples prepared under different conditions have been studied. Hydrogen bonding and transport properties have been linked: to exhibit good transport properties the material has to present a peculiar microstructure revealed by the hydrogen bonding. However, the hydrogen bonding and/or content in this structure has to be adjusted via the deposition conditions to reach an optimum hydrogen incorporation leading to the best layer and the best solar cell device.