Lifetime and efficiency degradation under illumination in boron (B) doped Czhochralski (Cz) based solar cells is well established and is attributed to the formation of boron and oxygen complexes. This paper shows that injection of carbon (C) from a SiCxNy antireflection (AR) coating can diffuse into the bulk silicon (Si) during high temperature contact firing and may compete with boron to reduce the number of B-O-2i defects and the corresponding LID. Reduction in LID due to additional carbon in the bulk was investigated quantitatively by fabrication and analysis of boron doped Cz cells coated with conventional SiNx as well as novel SiCxNy films deposited from an organosilicon source. SiCxNy coated cells showed an average loss of 0.1% in absolute efficiency due to LID compared to 0.3% loss in absolute efficiency for the counterpart SiNx coated solar cells fabricated on similar to 2 Omega cm Cz Si with an oxygen concentration of similar to 7 x 10(17) cm(-3). This phenomenon is attributed to the formation of carbon-oxygen dimmers (CO2i) which compete with the formation of B-O2i complexes. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3590741] All rights reserved.