The authors investigate the light-trapping efficiency of nanoimprinted ceramic grating reflectors for crystal silicon photovoltaic cells. Using 25 mu m silicon wafers as a model system and hemispherical reflection measurements, they demonstrate a 4%-6% increase in AM 1.5 solar-photon absorption for one-dimensional square and sinusoidal gratings compared to flat reflectors. The extrapolated increase in a short-circuit current for a 2 mu m thick silicon film cell due to diffractive light trapping is 20%. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3498754]