High-performance metal-free solar cells using stamp transfer printed vapor phase polymerized poly(3,4-ethylenedioxythiophene) top anodes

The use of vapor phase polymerized poly(3,4-ethylenedioxythiophene) (VPP-PEDOT) as a metal-replacement top anode for inverted solar cells is reported. Devices with both i) standard bulk heterojunction blends of poly(3-hexylthiophene) (P3HT) donor and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C60 (PCBM) soluble fullerene acceptor and ii) hybrid inorganic/organic TiO2/P3HT acceptor/donor active layers are studied. Stamp transfer printing methods are used to deposit both the VPP-PEDOT top anode and a work function enhancing PEDOT:polystyrenesulphonate (PEDOT:PSS) interlayer. The metal-free devices perform comparably to conventional devices with an evaporated metal top anode, yielding power conversion efficiencies of 3% for bulk heterojunction blend and 0.6% for organic/inorganic hybrid structures. These encouraging results suggest that stamp transfer printed VPP-PEDOT provides a useful addition to the electrode materials tool-box available for low temperature and non-vacuum solar cell fabrication.