Usually, the conductivity of semiconductor can be increased after phosphorus (P) doping but the electron mobility will be obviously reduced due to the strong impurity scattering. Here, we report a novel phenomenon that the carrier mobility in Si nano-crystals is significantly enhanced after nanoscale P doping. It is found that the electron mobility reaches to 30.3 cm2/V s, which is improved by one order of magnitude compared with that of un-doped one (1.6 cm2/V s), while the room temperature conductivity is as high as 1.5 x 103 S/cm by appropriately P doping. The clear experimental evidences are present to demonstrate that both the reduction of barrier height of grain boundaries and the surface defects states due to P doping improve the corresponding electron mobility in nano-crystalline Si films. (C) 2017 Elsevier B.V. All rights reserved.