Microcrystalline silicon solar cells with an open-circuit voltage surpassing the 600 mV barrier were prepared by combining the use of a hot wire deposited p-i interface with that of an i layer deposited by radio-frequency parallel plate plasma deposition using controlled Si H4 flow profiling. The control of the bulk and interface properties facilitated effective charge carrier collection from i layers with a crystalline volume fraction as low as ∼30%. Judging from the absorption in the infrared and the excellent charge carrier transport, the optoelectronic properties of this material were still dominated by the crystalline rather than the amorphous phase. © 2007 American Institute of Physics.