Embodiments of the present invention generally relate to solar cells and methods and apparatuses for forming the same. More particularly, embodiments of the present invention relate to thin film multi-junction solar cells and methods and apparatuses for forming the same. Embodiments of the present invention also include an improved thin film silicon solar cell, and methods and apparatus for forming the same, where one or more of the layers in the solar cell comprises at least one amorphous silicon layer that has improved electrical characteristics and mechanical properties, and is capable of being deposited at rates many times faster than conventional amorphous silicon deposition processes.