Replacing the aluminum back contact of screen-printed multicrystalline silicon solar cells by a novel low-temperature layer sequence boosts the absolute power conversion efficiency eta by Delta eta = 0.4%. The optimized hydrogenated amorphous silicon (a-Si:H)-based back side junction provides efficient back side passivation and contacting at the same time. The improved passivation quality reduces the effective surface recombination velocity S(eff) to S(eff)<20cm s(-1). Due to the optimized back side layer sequence, the open circuit voltage V(OC) rises by Delta V(OC) = 15 mV up to V(OC) = 622 mV and the short circuit current increases by Delta J(SC) = 0.8 mA cm(-2). (C) 2008 Elsevier B.V. All rights reserved.