Herein n-type hydrogenated nano-crystalline silicon (nc-Si:H) thin films were synthesized using silane (SiH4) and phosphine (PH3) acted as a dopant gas by catalytic chemical vapor deposition technique (Cat-CVD). The substrate temperature was maintained at 200 °C. The effect of PH3 flow rate on opto-electronic and structural properties of nc-Si:H was studied using UV-visible spectroscopy, dark conductivity, low angle X-ray powder diffraction (XRD), Raman spectroscopy, etc. From low angle XRD and Raman analysis, it was observed that the incorporation of phosphorus atoms in nc-Si:H caused the transformation nc-Si:H to a-Si:H. At optimized PH3 flow rate (0.3 sccm), n-type nc-Si:H films from a high deposition rate (~ 29.6 Å/s) had an optimum band gap (~ 1.89 eV), high dark conductivity (~ 1.52 S/cm) and low charge carrier activation energy (0.19 eV) at low hydrogen content (~ 1.83 at. %). The deposited films can be useful as n-layer Si:H based c-Si heterojunction solar cells.