Cathodes comprising highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) for semi-transparent polymer solar cells

Semi-transparent polymer solar cells from a blend of poly-(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) comprising a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) cathode and a vacuum deposited n-doped organic buffer layer have been realized. Among the investigated organic material systems for n-doping, the use of lithium doped bathophenanthroline (BPhen:Li) allowed for proper energy level alignment and subsequently for an open-circuit voltage Voc ≈ 600 mV. Upon deposition the PEDOT:PSS adheres selectively on the BPhen:Li buffer layer in order to form the laterally defined transparent cathode.