Transparent conductive oxides for coating applications

Abstract

Transparent, conductive oxides (TCOs) applied as coatings find multiple applications in various areas such as flat panel display setups, as electrodes in touch-screen panels, electrochromic devices, slar cells and in architectural applications for example as IR reflectors. The favored material in the class of TCOs is still ITO - Sn-doped In2O3 - due to its unique combination of high transparency and electrical conductivity. Though already very good, the potneital of the ITO coatings with regard to their conductivity leaves some space for future improvements. Also ITO as a material has some serious drawbacks, such as limitied availability and high costs. This work presents some strategies to overcome these obstacles. One way to enhance the conductivities of alternative materials is to use carbon nanotubes as a dopant. This strategy was tested for ATO (Antimony-doped Tin Oxide), Titan dioxide and AZO (Aluminium-doped Zinc oxide). The results for these materials are presented. In coatings of ITO on glass or polymeric foils usually silica-based binders are used. They have the disadvantage to reduce the contact between the highly conducting grains and thus reduce overall conductivity in the composite. The matrix between the nanoparticles can be improved by serveral measures. Experiments with relevance in this direction are discussed. A third strategy aims at the reduction of costs in the process of ITO fabrication. Here one way to go is to use in electrochemical synthesis method. Results of the line of development are presented. Other strategies comprise the suitable processing of materials with a lower intrinsic conductivity or the search for materials with high intrinsic conductivity close to that of ITO. Exmples are presented and discussed.