Rapid thermal processing to enhance PECVD SiN-induced hydrogenation in high-efficiency EFG silicon solar cells

Rapid thermal processing (RTP) is studied to improve the bulk lifetime and efficiency of EFG Si solar cells. The RTP firing of PECVD SiN on the front and screen-printed Al on the back at 750°C with a fast cooling rate is found to increase the bulk lifetime of EFG Si from 1-3 μs to ∼50 μs due to enhanced SiN-induced hydrogen passivation of defects. This increase is believed to be enhanced due to a synergistic interaction between atomic hydrogen and vacancies. For screen-printed EFG Si solar cells, RTP firing is found to be superior to a conveyor belt furnace firing, resulting in 0.4% higher average absolute cell efficiency. Rapid firing improves back surface field, contacts, and retention of hydrogen at defects. An optimized RTP firing process produces high-efficiency EFG Si solar cells with single layer SiN antireflection coating: 15% efficiency with screen-printed contacts and 15.8% efficiency with photolithography contacts.