We describe the properties of nano-crystalline silicon based alloy (nc-SiXY) prepared by a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique with silane (SiH4) and XY gas mixtures and diluted in hydrogen (H2) at low deposition temperature. Varying the gas ratio among SiH4, H2 and XY gasses could alter the optical bandgap and structure. The nc-Si films with high crystalline volume fraction were first prepared, and then the XY gasses were added in order to tune the microstructure and opto-electronic properties of this nano-crystalline silicon based alloy. We have characterized the materials using UV-VIS-NIR, Raman, Constant Photocurrent Method (CPM), dark- and photo-conductivity. As XY gas flows were increased, the optical bandgap of nc-SiXY films increased, while its crystalline volume fraction and conductivity decreased. With proper control of the silane concentration, XY/SiH4 gas ratio, and deposition pressure, we have fabricated the nc-SiXY film with optical bangap of about 1.5eV. Applying this material as the absorber layer in p-i-n devices with configuration of textured ZnO/nc-p+/nc-SiXY/a-n+/Ag, the efficiency is 7.25% (Voc=0.616V, Jsc=17.69mA/cm2, FF= 0.666) with thickness of ∼0.8μm.