Silicon ribbon with varying oxygen concentrations grown by the edge‐defined film‐fed growth technique has been annealed for periods of up to 1 h at 1200 °C prior to fabrication into solar cells. Low (<1×1016atom/cc interstitial) oxygen content ribbon cell performance, which is characteristically depressed with respect to higher (∼5×1016atom/cc interstitial) oxygen content ribbon, is improved by the anneal to levels approaching those observed in unannealed ribbon with the higher oxygen concentrations. The latter are essentially unaffected by the anneal. An explanation for ribbon cell property responses is proposed that is based on consideration of recombination effects associated with carbon microdefects.