Hydrogenated films of silicon nitride (SiNx:H) were investigated by varying the deposition condition in plasma enhanced chemical vapor deposition (PECVD) reactor and annealing condition in infrared (IR) heated belt furnace to find the optimized condition for the application in multicrystalline silicon solar cells. By varying the gas ratio (ammonia to silane), the silicon nitride films of refractive indices 1.85-2.45 were obtained. Despite the poor deposition rate, silicon wafer with the film deposited at 450 degrees C showed the best minority carrier lifetime. The film deposited with the gases ratio of 0.57 showed the best peak of carrier lifetime at the annealing temperature of 800 degrees C. The performance parameters of cells fabricated by varying co-firing peak temperature also showed the best values at 800 degrees C. The multicrystalline silicon (mc-Si) solar cells fabricated in conventional industrial production line applying the optimized film deposition and annealing conditions on large area substrate (125 mm x 125 mm) was found to have the conversion efficiency of 15%. (c) 2006 Elsevier B.V. All rights reserved.