Flexible transparent conductive coatings by electrospinning

Transparent conductive coatings are widely used as transparent conductive electrodes in displays, touch screens, solar cells, antenna structures etc., and require a low sheet resistance combined with a high transmission. For wearable electronics and bendable displays, a flexibility of the electrode material is also required. Electrospinning was used as a facile method to produce very long and thin fibers, and in combination with silver, conductivity was introduced.
The properties of silver (Ag) nanoparticle-containing inks and coatings thereof, applied by electrospinning on PET and PC foil substrates were studied. The tested Ag nanoparticle-containing inks consisted of a commercial nanoparticulate silver ink and a polymeric binder in a suitable solvent. The electrospun fibers were fabricated using different spinning conditions and were then silver plated in an electroless process. The resulting coatings have been characterized with respect to their sheet resistance, transmission, and haze.
It was observed that with the electrospun polymer silver fibers, fibers with a diameter of about 1 to 3 µm and lengths of several cm could be obtained, ensuring a high percolation. By variation of the number and the diameter of the fibers, the conductivity and the optical properties could be improved, and coatings with a sheet resistance below 5 Ω/sq were obtained, showing a high transmission of up to 92 % and a low haze below 2 %.
The achieved sheet resistances in combination with the relatively high transmission are comparable to those of other transparent conductive coatings that are state of the art and available on the market, such as ITO coatings. In addition, the coatings produced by this electrospinning process are flexible and stretchable, which offers interesting new applications for wearable electronics and 3D-formable displays, for example. Other advantages of these coatings are the low-cost process for their production and the possibility of upscaling by a roll-to-roll process.