Vacuum-free and metal electrode-free organic tandem solar cells

We report on vacuum-free and metal electrode–free organic tandem solar cells that use conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the top electrode. The PEDOT:PSS top electrode was deposited via film-transfer lamination that does not need high-vacuum processing. The fabricated tandem solar cells exhibit an open-circuit voltage of 1.62 V, which is nearly the sum of the VOC of individual subcells, a high fill factor up to 0.72, and averaged power conversion efficiency of 3.6% under 100 mW cm−2 AM 1.5 illumination. The effect of the patterning of charge recombination layer and electrodes on the device performance has also been discussed.