Stable and highly conductive carbon nanotube enhanced PEDOT:PSS as transparent electrode for flexible electronics

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a popular polymeric material for solution-processed transparent conductive electrodes (TCE), especially on flexible substrates. PEDOT:PSS electrical properties are often improved with a variety of additives. Here, we present an innovative way to furtherly improve the performances of this material by incorporating single walled carbon nanotubes (SWCNTs) into commercially available conductive PEDOT:PSS formulation (Heraeus Clevios™ FE-T). With a load of 0.01 wt% SWCNT, we observed the best trade-off between transparency (91.0% at 550 nm) and sheet resistance (89.1 Ω sq−1). Moreover, we developed a simple and effective lithographic structuring process for these TCEs and we investigated the process effects on its optoelectronic and morphological properties. The developed SWCNT/FE-T electrodes, processed on both glass and flexible PET substrates, were incorporated in organic photodiodes (OPDs), with P3HT:PCBM as active layer. These OPDs show dark current densities, on-off ratios and external quantum efficiencies (EQE) comparable to reference devices comprising indium-tin-oxide (ITO) as TCE. Additionally, this TCE shows superior mechanical and chemical stability, under bending and damp-heat test condition compared to ITO and PEDOT:PSS, respectively.