Low-Cost Fabrication of Organic Photovoltaics and Polymer LEDs - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 236

Fig. 12 Illustration of the multilayer structure and the solutions of the functional layers

brittleness. Moreover, the flexible ITO sputtered on PET substrate has less
transmittance and conductivity than that of the ITO-glass. There are many can-
didates for the alternative transparent electrodes such as metal mesh, silver
nanowire [ 11 ], graphene [ 12 ], carbon nanotubes [ 13 ], and conducting polymer
[ 14 ]. The conducting polymer of PEDOT:PSS fabricated by roll-to-roll coating
offers satisfactory optical transparency and electrical conductivity (Fig. 13 )as
polymer anode. For example, a 200 nm thick polymer anode (PEDOT:PSS, H.C.
Stock PH1000) can be coated by roll-to-roll blade-slit coating method over large
substrate at one time without wasting of the solution as shown in Fig. 14 .In
comparison, spin coating method requires three time coatings and wasting lots of
solutions to cast the same 200 nm thick polymer anode. The sheet resistance of the
polymer anode made by roll-to-roll coating is around 40 X/sq, when the thickness
is 250 nm. The transmittance including PET substrate of the polymer anode is
74 % at 550 nm wavelength. For a thinner, 120 nm thick polymer anode, the sheet
resistance is 110 X/sq and the transmittance is around 85 %.