A new back surface passivation stack for thin crystalline silicon solar cells with screen-printed back contacts

In order to manufacture high-efficiency Si solar cells with a passivated rear surface and local contacts, it is necessary to develop both an excellent rear-passivation scheme compatible with screen-printing technology and a robust patterning technique for local contact formation. In this work, we have fabricated Si solar cells on similar to 130 mu m thick substrates using manufacturable processing, where rear side was passivated with a plasma-enhanced chemical vapor deposited SiOx/SiNx/SiOxNy stack and local back contacts using laser. As a result of both the rear surface passivation stack and the laser-fired local contacts, cell efficiencies of up to 17.6% on a 148.6 cm(2) Float-zone Si wafer and 17.2% for a 156.8 cm(2) multicrystalline Si wafer were achieved. PC-1D calculations revealed that the cells had a back surface recombination velocity (BSRV) of similar to 400 cm/s and a back surface reflectance (BSR) of over 90%, as opposed to standard full Al-BSF cells having a BSRV of similar to 800 cm/s and a 70% BSR. This result clearly indicates that the new technique of the passivation scheme and the patterning using laser developed in this study are promising for manufacturing high-efficiency PERC-type thin Si solar cells. (C) 2010 Elsevier B.V. All rights reserved.