Implementation of rapid thermal processing to achieve greater than 15% efficient screen-printed ribbon silicon solar cells

This paper summarizes our progress in fabricating record-high efficiency ribbon Si solar cells with screen-printed and photolithography defined contacts. We have developed and optimized rapid thermal processing enhanced SiN/sub x/-induced hydrogenation to achieve record-high efficiency screen-printed EFG (15.9%) and String Ribbon (15.6%) cells and a high-efficiency string ribbon cell (17.8%) with photolithography defined contacts. A low-frequency SiN/sub x/ film and a two-step RTP firing process were critical in achieving high-efficiency screen-printed cells. Step 1 provides SiN/sub x/ induced hydrogenation and forms an aluminum doped back surface field. Step 2 is designed for Ag grid firing and includes rapid cooling to retain hydrogen introduced in Step 1.