19.4%-efficient large-area fully screen-printed silicon solar cells

We demonstrate industrially feasible large-area solar cells with passivated homogeneous emitter and rear achieving energy conversion efficiencies of up to 19.4% on 125 x 125 mm(2) p-type 2-3 Omega cm boron-doped Czochralski silicon wafers. Front and rear metal contacts are fabricated by screen-printing of silver and aluminum paste and firing in a conventional belt furnace. We implement two different dielectric rear surface passivation stacks: (i) a thermally grown silicon dioxide/silicon nitride stack and (ii) an atomic-layer-deposited aluminum oxide/silicon nitride stack. The dielectrics at the rear result in a decreased surface recombination velocity of S-rear = 70 cm/s and 80 cm/s, and an increased internal IR reflectance of up to 91% corresponding to an improved J(sc) of up to 38.9 mA/cm(2) and V-oc of up to 664 mV. We observe an increase in cell efficiency of 0.8% absolute for the cells compared to 18.6% efficient reference solar cells featuring a full-area aluminum back surface field. To our knowledge, the energy conversion efficiency of 19.4% is the best value reported so far for large area screen-printed solar cells. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim