AMORPHOUS Si/SiN DOUBLE LAYERS: A LOW-TEMPERATURE PASSIVATION METHOD FOR DIFFUSED PHOSPHORUS AS WELL AS BORON EMITTERS

摘要

Boron-doped emitters are passivated by amorphous silicon/silicon nitride double layers formed by plasma enhanced chemical vapor deposition at 230 ℃. An emitter saturation current density of 18 fA/cm~2 is achieved on a 90 Ω/sq phosphorus-diffused emitter, and of 24 fA/cm~2 on a 225 Ω/sq boron-diffused emitter, respectively. We optimize the thickness of the amorphous silicon film for maximum efficiency of p-type silicon solar cells. The optimum a-Si thickness is in the range of 5 nm < d < 10 nm, combining high quality surface passivation with low optical absorption. The passivation is stable under UV irradiation, and during annealing up to 500 ℃.