Quality improvement of screen-printed Al emitter by using SiO2 interfacial layer for industrial n-type silicon solar cells

This paper reports on an industrially applicable approach to create efficient Al-doped p+ regions alloyed from screen-printed pastes for the application as rear emitters in n-type silicon solar cells. The influences of polished and pyramidal rear surfaces on the formation of Si-Al alloy and saturation current are discussed. We demonstrate that a thin SiO2 layer on Si-Al interface can mitigate the inhomogeneous Al diffusion during alloying process and develop the transport properties. Furthermore, we apply this SiO2 layer in our n+np+ solar cells, which exhibit lower series resistance and fine IQE response as a result of the improved Al emitter quality. For large-area n-type silicon solar cells (239 cm2) with a full-area Al-p+ rear emitter, we achieved an 18.8% efficient cell with an open-circuit voltage of 637.4 mV. Remarkable gains of 1.6% on average efficiency, 0.8 mA/cm2 on Jsc, 8.6 mV on open-circuit voltage and 4.1% on FF are obtained, comparing with the solar cells fabricated by standard industrial process.