(Georgia Institute of Technology, 2003-05)
Rohatgi, Ajeet; Yelundur, Vijay; Jeong, Ji-Weon; Kim, Dong Seop; Gabor, A. M.
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(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(x) film and a two-step RTP firing process were critical in achieving high-efficiency screenprinted
cells. Step 1 provides SiN(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.
(Georgia Institute of Technology, 2000-09)
Yelundur, Vijay; Rohatgi, Ajeet; Jeong, Ji-Weon; Gabor, A. M.; Hanoka, J. I.; Wallace, R. L.
To improve the bulk minority carrier lifetime in String Ribbon silicon, SiN(x) induced defect passivation during a post deposition anneal is investigated. Our results indicate that SiN(x) induced hydrogen passivation is very effective when the SiN(x) film is annealed in conjunction with a screen-printed AI layer on the back. In addition, it is found that controlled rapid cooling can be used to enhance
the defect passivation process. A model is proposed which relates the high temperature passivation to the release of hydrogen from the SiN(x) film, the injection of vacancies from backside AI alloying, and the retention of hydrogen at defect sites. High efficiency screen-printed String Ribbon solar cells (>14.5%) are fabricated utilizing the simultaneous SiN(x)/AI anneal in a belt furnace for hydrogenation and AI-BSF formation, followed by RTP firing of screen-printed contacts to improve the retention of
hydrogen at defects.