Rapid Thermal Technologies for High Efficiency Silicon Solar Cells
Cho, Y. H.
Hilali, Mohamed M.
Ruby, D. S.
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This paper shows that rapidly formed emitters (≤ 6 min) in a conveyor belt furnace or 3 minutes in an RTP system, in conjunction with a screen-printed (SP) RTP Al-BSF and passivating oxide formed simultaneously in 2 minutes can produce high efficiency cells with no surface texturing, point contacts, or selective emitter. It is shown for the first time that an 80 Ω/ emitter and SP Al-BSF formed in a high throughput belt furnace can produce 19% FZ cells, 18.4% MCZ cells and greater than 17% CZ cells with photolithography (PL) contacts. Using PL contacts, we also achieved 19% efficient cells on FZ, >18% on MCZ, and ~17% boron-doped CZ by emitter and SP Al-BSF formation in less than 10 minutes in a single wafer RTP system. Finally, a manufacturable process with 45 Ω/ emitter and screen-printed (SP) Al-BSF and Ag contacts formed in the conveyor belt furnace gave 17% efficient cells on FZ silicon. Compared to the photolithography cells, the SP cell gave ∼2% lower efficiency along with a decrease in Jsc and fill factor (FF). This loss in performance is attributed to a combination of the poor blue response, higher series resistance and higher contact shading in the SP devices.