A method and apparatus are provided for formation of a composite material on a substrate. The composite material includes carbon nanotubes and/or nanofibers, and composite intrinsic and doped silicon structures. In one embodiment, the substrates are in the form of an elongated sheet or web of material, and the apparatus includes supply and take-up rolls to support the web prior to and after formation of the composite materials. The web is guided through various processing chambers to form the composite materials. In another embodiment, the large scale substrates comprise discrete substrates. The discrete substrates are supported on a conveyor system or, alternatively, are handled by robots that route the substrates through the processing chambers to form the composite materials on the substrates. The composite materials are useful in the formation of energy storage devices and/or photovoltaic devices.