Gravure-printed PEDOT:PSS on flexible PEN substrate as ITO-free anode for polymer solar cells

摘要

In this work, highly conductive and transparent films based on poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped with dimethyl sulfoxide (DMSO) were printed onto a flexible substrate, the polyethylene naphthalate (PEN), using the gravure printing method. Gravure-printed DMSO-PEDOT:PSS ink suitably modified with isopropanol was developed and used as anode in flexible solar cells replacing the commonly used anode, that is, Indium Tin Oxide (ITO). Several inks were prepared and characterized in terms of viscosity and surface energy and tested by gravure printing. The wettability of the PEN substrate was investigated through contact angle measurements. For comparison, the anodic conductive polymer was also spin coated on the PEN substrate using an ink suitable for this technique. The films produced with both the techniques, gravure printing and spin coating, each using a proper ink, were characterized in terms of structure and physical-chemical properties. The printed layers were employed as anodes into ITO free-polymer solar cells based on a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C-70-butyric acid methyl ester ([70]PCBM). The performances of the devices with printed and spin coated polymeric anode were compared. The cell with the spin-coated anode reached a power conversion efficiency of 3% while the corresponding device with the printed anode a value around 2%. POLYM. COMPOS., 36:1104-1109, 2015. (c) 2015 Society of Plastics Engineers