Polymer Supported and Freestanding Transparent Electrodes Produced By Ink-Jet Printing and Electrodeposition

Transparent conductive electrodes play an important role in different applications, as thin-film solar cells, flat-panel displays and light emitting diodes^1-3. With the increasing demand arising from flexible devices, mechanical properties of electrodes are becoming more and more important and alternatives to traditional materials are being investigated^4,5. Doped metal oxides, e.g. ITO, are mostly used at the moment, but their main limitation derives from their ceramic nature that makes them brittle and therefore prone to cracking, when deposited on flexible substrates⁶. We studied the production of metallic micronets, with the aim of finding an alternative to ITO for transparent conductive electrodes. The use of metals, which are the materials owning the highest performances in terms of electrical conductivity, allows maintaining the desired level of transparency of the electrode, given by the optimization of the geometrical parameters of the micro-net.  Both polymer supported and free standing metallic micronets were produced. To obtain the former structure, a conductive Ag pattern was printed on PET substrate using ink-jet printing (an example is shown in Figure 1), and then a copper layer can be grown by electrodeposition on the silver printed lines, to obtain the freestanding structure. Release of the metallic micro-net from the PET substrate is spontaneously obtained during the electrodeposition step. Electrical and optical properties of the produced electrodes were investigated. The free-standing metallic micro-net has resistivity two orders of magnitude lower than a commercially available sample of ITO-coated PET, while maintaining high transparency.

Figure 1: SEM image of Ag pattern printed on PET substrate

References

1. S. Reineke, F. Lindner, G. Schwartz, N. Seidler, K. Walzer and K. Leo, Nat. Lett., 459, 234 (2009).

2. A. C. Arias, J. D. MacKenzie, I. McCulloch, J. Rivnay and A. Salleo, Chem. Rev., 110, 3 (2010).

3. J. J. Shiang, Interface, 18, 37 (2009).

4. H. Chang et al., Adv. Funct. Mater., 20, 2893 (2010)

5. L. Hu et al., ACS Nano, 4, 2955 (2010)

6. Z. Chen, Thin Solid Films, 394, 201 (2001)