Method for efficiently passivating back side of crystalline silicon solar cell

The invention discloses a method for efficiently passivating back side of a crystalline silicon solar cell. The method is characterized by comprising the following steps of: (1) reversely inserting etched silicon chip into a PECVD (plasma enhanced chemical vapor deposition) graphite boat, and feeding to a PECVD furnace tube; (2) vacuumizing the furnace tube; (3) pre-processing the furnace tube; (4) testing the pressure; (5) depositing a first silicon oxynitride film, wherein the temperature is 460 DEG C; the ammonia flow is 2.5-3.8slm; the silicane flow is 1100-1800sccm; the nitrous oxide flow is 500-800sccm; the radio-frequency power is 6000W, and the lasting time is 2-5min; (6) blowing by 5slm of nitrogen for 30 seconds; vacuumizing to 80mTorr, and depositing a second silicon nitride film, wherein the temperature is 465 DEG C; the ammonia flow is 5-8slm; the silicane flow is 700-950sccm; the radio-frequency power is 6000W, and the lasting time is 3min, and (7) blowing and cooling by the nitrogen. The back p