1. Field of Invention
The field of the currently claimed embodiments of this invention relates to solution processes for producing electrodes for electro-optic devices and devices that use the electrodes.
2. Discussion of Related Art
The most dominant transparent conductive film currently in use for electro-optic devices, such as liquid crystal displays, touch-screen displays and photovoltaic cells, for example, is Indium-Tin-Oxide (ITO). High transparency and low sheet resistant have ensured its wide application in many areas. Although it has been used for several decades, there is significant interest in developing alternatives to ITO because of the decreasing availability, and accompanying increase in price, of indium. Due to the high and increasing demand for transparent electrodes, and the limited supply of indium, there is currently an urgent need for new transparent electrodes.
There are several candidates for transparent electrodes based on materials that can potentially replace ITO. These include the use of carbon nanotubes (CNT), graphene, or thin metal films, for example. However, these candidates all have disadvantages that they compromise between optical transparency and electrical conductivity.
Recently, some efforts have been directed to using silver nanowire (AgNW) networks to form transparent conductors. There are several issues that remain to be addressed for the large scale fabrication of AgNW films. First, a good electrical connection between crossed AgNWs is a key factor to achieve high conductivity. However, due to surfactant coating of PVP on the surface of AgNW, extra processes are often utilized to fuse the crossed AgNWs together. These processes include high temperature thermal annealing (>150 ° C.), applying extra pressure or vacuum filtering on anodized aluminum oxide (AAO) membrane substrates and HCl vapor treatment, etc. Second, strong adhesion between AgNW and substrates is necessary to obtain stable and robust AgNW fibrous films. Substrate surface modification has been used to improve the adhesion of AgNWs on the substrate. Burying AgNW into polymer films by applying pressure can also provide strong adhesion between AgNWs and substrates. Moreover, nail polish or in-situ polymerization has also been reported to improve the adhesion. However, these efforts have not provided transparent electrodes and methods of production that are adequate to replace ITO. Therefore, there remains a need for improved transparent electrodes, methods of producing the electrodes, and devices that use the electrodes.