Surface Passivation and Simulated Performance of Solar Cells With Al ₂O₃/SiN ₓ Rear Dielectric Stacks

Al2O3/SiNxstacks that are prepared at low temperatures in chemical vapor deposition processes excel in terms of surface passivation applicable in industrial p-type Si solar cells. The conversion efficiencies that are feasible for solar cells with Al2O3/SiNxrear dielectric stacks, have been investigated by numerical simulations, including the optical performance of the stacks, which was considered for various Al2O3and SiNxfilm thicknesses. The optically optimized film thicknesses were found to be 15-30 nm for Al2O3and 100-120 nm for the SiNxfilms. Experimentally, the surface passivation was found to be similar for annealed Al2O3/SiNxstacks and single-layer Al2O3films with an almost equal level of field-effect and chemical passivation, as determined by optical second harmonic generation and corona charging experiments.