In studies of hydrogenated amorphous silicon (a-Si:H) n-i-p solar cells fabricated by rf plasma-enhanced chemical vapor deposition PECVD, we have found that the maximum open circuit voltage (V oc) is obtained by incorporating p-type doped Si:H layers that are protocrystalline in nature. Specifically, these optimum p layers are prepared by PECVD in the a-Si:H growth regime using the maximum hydrogen-to-silane flow ratio possible without crossing the thickness-dependent transition into the mixed-phase (amorphousmicrocrystalline) growth regime for the 200 Å player thickness. The strong dependence of the player phase and solar cell V oc on the underlying i-layer phase also confirms the protocrystalline nature of the optimum Si:H p layer.