||In this thesis, surfaces of bulk Si solar cells were passivated by direct growth of SiO2 thin films using supercritical CO2 (SCCO2) treatments with H2O2 and by SCCO2 treatments to sputtered SiO2 thin films. The passivation layer of a conventional Si solar cell can be as thick as 100 nm, so the sintering temperature as high as 850℃ is used to form a good ohmic contact to the cell surface. If the passivation layer thickness is under 10 nm, the sintering temperature and cost can be decreased significantly. The electrical properties including I-V and C-V of the SiO2 films prepared at different thickness of sputtered SiO2 and SCCO2 treatments were discussed. In addition, these techniques were employed in processes of bulk single crystal silicon solar cells.|
If no passivation layer was used, the conversion efficiency of a bulk single-crystal silicon solar cell is 7.08% under AM1.5 (1000W/m2) radiation. The measured short-circuit current density, open-circuit voltage, fill factor are 36.43 mA/cm2、0.501 V and 0.35, respectively. But when SCCO2 treatments were used after sputtering, for passivating sputtered SiO2 thin films the conversion efficiency of the silicon solar cells increased to 11.58% under AM1.5 radiation at a sintering temperature of 300℃. The measured short-circuit current density, open-circuit voltage, fill factor are 40.36 mA/cm2、0.558 V and 0.46, respectively. The conversion efficiency was increased drastically with the proposed techniques.