Highly conductive PEDOT:PSS electrode by simple film treatment with methanol for ITO-free polymer solar cells

Abstract

We proposed a simple yet robust film treatment method with methanol having only one hydroxyl group to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by four orders of magnitude. Different methods of film treatment: immersing PEDOT:PSS film in the methanol solution; dropping methanol on the film; and a combination of these are employed and the results are compared. The conductivity of PEDOT:PSS films was enhanced from 0.3 S cm À1 to 1362 S cm À1 after film treatment with methanol. Other alcohols like ethanol and propanol were also used to treat the PEDOT:PSS film and showed inferior conductivity enhancement compared to methanol. The conductivity enhancement was greatly affected by the hydrophilicity and dielectric constant of the alcohols used. The mechanism of conductivity enhancement was investigated through various characterization techniques including FTIR, XPS and AFM. Removal of the insulator PSS from the film, and morphology and conformational changes are the mechanisms for the conductivity enhancement. The treated films also showed high transmittance and low sheet resistance desirable for a standalone electrode. ITO-free polymer solar cells were fabricated using PEDOT:PSS electrodes treated with methanol and showed almost equal performance to ITO electrodes.

Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

“…This has been driven by escalating indium costs, energy intensive manufacturing requirements for ITO 1 and concerns over release of indium and oxygen into active 2 layers, particularly of organic devices. 2 Numerous candidates have been identified as transparent electrodes ranging from polymeric systems, 3 carbon nanotubes, 4 graphene, 5 metallic nanostructures 6 and doped metal oxides. 7 Of these candidates, doped metal oxides are of particular interest owing to their ease of fabrication, suitability for large area processing, low-cost and tuneable electronic properties.…”

Fully Solution-Processed Semitransparent Organic Solar Cells with a Silver Nanowire Cathode and a Conducting Polymer Anode

“…1 ITO, however, suffers from several drawbacks that limit its viability as a TCE for next-generation optoelectronics, including high cost, poor performance on plastic substrates, and a tendency to crack when flexed. 2,3 Potential solution-processable alternatives to ITO include carbon nanotubes, 4,5 graphene, [6][7][8][9] conducting polymers, 10,11 and metal nanowires [12][13][14][15] Single-Walled Carbon Nanotubes (SWCNTs) are attractive TCE materials due to their high intrinsic conductivity and mechanical durability but, owing to large inter-tube resistances, their reported performance characteristics are significantly worse than ITO. The need for aggressive acid treatments to induce p-type doping of semiconducting tubes and the non-permanent nature of the doped state are also problematic.…”

Comparison of dimethyl sulfoxide treated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) electrodes for use in indium tin oxide-free organic electronic photovoltaic devices

“…The conductivity can also be enhanced by post-treatment of the PEDOT:PSS film. sulphuric acid [20], and low boiling point organic solvents such as methanol and ethanol used singularly or as a co-solvent can be dropped onto a PEDOT:PSS film [21,22]. Immersing pre-formed PEDOT:PSS films in a polar organic solvent like ethylene glycol has also been shown to improve the intrinsic conductivity of PEDOT:PSS films [23].…”