Cost-effective and Scalable Manufacturing of Metal-mesh Transparent Electrodes for Flexible Applications

Abstract

Transparent conducting electrodes (TCEs) are key materials in optoelectronic devices such as displays, light-emitting diodes (LEDs), touchscreens, solar cells, and smart windows. For better performance of these devices, it is important to develop transparent electrodes with low sheet resistance while maintaining good optical transparency. Currently the dominant materials for TCEs are thin films of transparent oxides (TCOs) demonstrating reasonably good electronic performances, but film brittleness, low infrared transmittance and low abundance limit its suitability for many industrial applications. To overcome these limitations, recently there have been several new generation TCEs based on graphene, carbon nanotube, metal nanowire networks and metal mesh is introduced.These alternative TCEs demonstrate much better performance in terms of optical transparency, electrical conductivity and flexibility, 5 however, materials and fabrication methods involved in its production are expensive and time-consuming which hinder its widespread commercial applications.

Over the past several years, we have developed cost-effective approaches for fabricating flexible transparent metal mesh electrodes via simple solution processed steps involving lithography, electroplating and thermal imprint transfer. Some of the techniques developed in this direction are being commercialized towards mass production. Generally, in our process, a prototypetransparent flexible copper metal-mesh electrode can be fabricated using five simple steps including: (i) mesh pattern formation into the spincoated polymer resist on FTO glass by lithography; (ii) deposition of copper by electroplating inside the trenches to form a uniform Cu mesh; (iii) etching the resist to get the bare Cu mesh on glass substrate; (iv) imprint the bare Cu mesh into the polymer film by thermal imprinting process; and (v) separation of the polymer film from the FTO glass to transfer Cu mesh to a flexiblepolymer substrate in embedded form. Variations of this process have been developed to achieve the better capability for mass production, higher pattern resolution, and more versatile choices of materials. Record-high performance has been demonstrated on the transparent electrodes fabricated using our approach. Various applications are being developed and will also be introduced.