Photovoltaic properties of 4 mu m thick microcrystalline silicon p-i-n solar cells have been studied, over a range of crystallinity determined using Raman spectroscopy. Low-crystallinity material (below 10%) appears to absorb disproportionately strongly in the infrared, possibly due to increased light scattering or to relaxation of the crystal momentum selection rule. A minimum in solar cell efficiency is observed under AM 1.5 illumination when V-OC approximate to 580 mV, with blue response most strongly affected. This is consistent with a reduction in electron mobility to a value below that of amorphous silicon for low-crystallinity material, in agreement with time-of-flight measurements. (C) 2009 Elsevier B.V. All rights reserved.