Solution-processed copper nanowire flexible transparent electrodes with PEDOT: PSS as binder, protector and oxide-layer scavenger for polymer solar cells

The easy oxidation and surface roughness of Cu nanowire (NW) films are the main bottlenecks for their usage in transparent conductive electrodes (TCEs). Herein, we have developed a facile and scaled-up solution route to prepare Cu NW-based TCEs by embedding Cu NWs into pre-coated smooth poly(3, 4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) films on poly(ethylene terephthalate) (PET) substrates. The so obtained Cu NW-PEDOT: PSS/PET films have low surface roughness (~70 nm in height), high stability toward oxidation and good flexibility. The optimal TCEs show a typical sheet resistance of 15 Ω·sq^-1 at high transparency (76% at λ = 550 nm) and have been used successfully to make polymer (poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester) solar cells, giving an efficiency of 1.4%. The overall properties of Cu NW-PEDOT: PSS/PET films demonstrate their potential application as a replacement for indium tin oxide in flexible solar cells.