Method for passivating crystal silicon surfaces
View Patent ↗In a method of making a c-Si-based cell or a μc-Si-based cell, the improvement of increasing the minority charge carrier's lifetime, comprising: a) placing a c-Si or polysilicon wafer into CVD reaction chamber under a low vacuum condition and subjecting the substrate of the wafer to heating; and b) passing mixing gases comprising NH 3 /H 2 through the reaction chamber at a low vacuum pressure for a sufficient time and at a sufficient flow rate to enable growth of an a-Si:H layer sufficient to increase the lifetime of the c-Si or polysilicon cell beyond that of the growth of an a-Si:H layer without treatment of the wafer with NH 3 /H 2 .
1. In a method of making a c-Si-based cell, the improvement of increasing the minority charge carrier's lifetime, comprising:
a) placing a c-Si or polysilicon wafer into a CVD reaction chamber under a low vacuum condition and subjecting the substrate of said wafer to heating; and
b) passing mixing gases comprising NH 3 and H 2 through said reaction chamber at a low vacuum pressure for a sufficient time and at a sufficient flow rate to enable growth of an a-Si:H layer sufficient to increase the minority charge carrier lifetime of said c-Si polysilicon cell beyond that of growth of an a-Si:H layer without treatment of said wafer with NH 3 and H 2 ; and
c) flowing SiH 4 over said wafer.
2. The method of claim 1 wherein in step a) said low vacuum condition is a pressure of about 10 −6 Torr.
3. The method of claim 2 wherein said heating of said wafer substrate is to a temperature of about 250° C.
4. The method of claim 3 wherein in step b) said low vacuum pressure is about 20 mTorr.
5. The method of claim 4 wherein the flow rate of NH 3 is in a range of from about 2 to about 10 sccm and the flow rate of H 2 is in a range of from about 0 to about 50 sccm.
6. In a method of making a μc-Si-based cell, the improvement of increasing the minority charge carrier's lifetime, comprising:
a) placing a μc-Si wafer into a CVD reaction chamber under a low vacuum condition and subjecting the substrate of said wafer to heating; and
b) passing mixing gases comprising NH 3 and H 2 through said reaction chamber at a low vacuum pressure for a sufficient time and at a sufficient flow rate to enable growth of an a-Si:H layer sufficient to increase the minority charge carrier lifetime of said μc-Si cell beyond that of growth of an a-Si:H layer without treatment of said wafer with NH 3 and H 2 .
7. The method of claim 6 wherein in step a) said low vacuum condition is a pressure of about 10 −6 Torr.
8. The method of claim 7 wherein said heating of said wafer substrate is to a temperature of about 250° C.
9. The method of claim 8 wherein in step b) said low vacuum pressure is about 20 mTorr.
10. The method of claim 9 wherein the flow rate of NH 3 is in a range of from about 2 to about 10 sccm and the flow rate of H 2 is in a range of from about 0 to about 50 sccm.
11. A diffuse-junction silicon solar cell characterized by improved charge carrier lifetime comprising a c-Si or polysilicon wafer with a top surface passivation layer of a-Si:H grown using SiH 4 after treatment of said c-Si or polysilicon wafer with a mixture of NH 3 and H 2 .
12. A diffuse-junction silicon solar cell characterized by improved charge carrier lifetime comprising a μc-Si wafer with a top surface passivation layer of a-Si:H grown using SiH 4 after treatment of said μc-Si wafer with a mixture of NH 3 and H 2 .