Effect of High Sheet Resistance Emitter Phosphorous Concentrations on Multicrystalline Silicon Solar Cell Performance
By Kurt R. Mikeska, Anke Zerres, Ben Whittle, Richard J.S. Young, Zhigang Li, and Liang Liang
Solar cell performance was evaluated for silver thick film pastes with different chemistries designed to manage the contact of 100ohm/sq emitters with systematic variations in the emitter phosphorous diffusion profiles. More specifically, the surface phosphorous concentrations [P] of the 100ohm/sq wafers were varied from approximate 3.0E20/cm3 to 1.0E21/cm3 and junction depths from 250nm to 450nm. These wafers were compared to 80ohm/sq emitters and industry standard 65ohm/sq emitters. 100ohm/sq emitters showed an increase in quantum efficiency (QE) in the blue region of the spectrum and a reduction in QE at high emitter surface [P]. Establishing high Fill Factors (FF) was dependent on the silver paste’s ability to contact the emitter without damaging the junction. 100ohm/sq emitters with high surface [P] showed improved performance due to improved contact resistance compared to 100ohm/sq emitters with lower surface [P]. Ag crystallite concentration at the silver-emitter contact interface was also dependent on the emitter surface [P] but did not correlate with improved performance.