Solution-processed transparent electrodes

Abstract

Typically, materials with high electrical conductivity such as metals are opaque, and materials with high optical transparency such as glass are insulating. Finding materials that are both transparent to visible light and electrically conductive has proven to be a challenge. The need for such materials continues to grow, as many of today's popular devices such as liquid-crystal displays and organic light-emitting diodes in televisions, touch screens in phones or tablet computers, electrophoretic displays in e-readers, or solar cells on a roof require one or more layers to transmit visible light, while simultaneously applying a voltage or conducting a current. Today, the industry's need for such a material is serviced by various metal oxides, of which indium tin oxide (ITO) is by far the most common. The opto-electronic properties of ITO satisfy industry need for most devices; however, ITO has several drawbacks (e.g., brittle, expensive, and typically applied via costly sputtering techniques). To address these issues, recent advances in solution-processed nanomaterials have enabled several printable alternatives to sputtered ITO. These nanomaterials include conducting polymers, metallic nanostructures, ITO nanostructures, carbon nanotubes, and graphene. The ability to apply nanomaterials from the liquid phase opens the possibility to print these electronic materials roll-to-roll, greatly reducing cost and increasing yield and throughput, while the nanomaterial topology enables truly flexible devices. © 2011 Materials Research Society.