Effect of Si content in Al paste on Local Al Rear Contacts in PERC Cell 
Supawan Joonwichien, Katsuhiko Shirasawa, Satoshi Utsunomiya, Hidetaka Takato
National Institute of Advanced Industrial Science and Technology (AIST), Koriyama, Fukushima, Japan

We investigated the effect of Si content in the Al paste on the characteristic of local Al contacts, and their impact on passivated emitter and rear cell (PERC) cell performance. We observed an increased open-circuit voltage (Voc) for PERC cells using Al paste with Si. This can be attributed to a thicker and more uniform local aluminum–back surface field (Al–BSF), including a lower void density. By adding Si to the Al paste, the driving force for Si diffusion during alloying is believed to be reduced, causing the increased rejected Si to form a thicker Al–BSF during cooling. This behavior of the Si could prevent the formation of voids, leading to an improvement in the cell performance. 

Area: Sub-Area 4.2: Standard pn-Junction Based Devices and Technologies