Methods for fabricating solar cells without the need to perform gasification of metallurgical-grade silicon are disclosed. Consequently, the costs and health and environmental hazards involved in fabricating the solar or silicon grade silicon are being avoided. A solar cell structure comprises a metallurgical grade doped silicon substrate and a thin-film structure formed over the substrate to form a p-i-n junction with the substrate. The substrate may be doped p-type, and the thin film structure may be an intrinsic amorphous layer formed over the substrate and an n-type amorphous layer formed over the intrinsic layer.