Highly Transparent ITO/Ag/ITO Sandwich Structure with an Ultra-Thin Silver Layer for Solar and Display Applications

A highly and evenly transparent conductive electrode is fabricated on glass substrate thanks to the ability to produce stable continuous ultra-thin silver films, the computational global search of optical properties on ITO/Ag/ITO (IAI) sandwich structures using the transfer matrix method (TMM), and annealing process in the air at high temperature. First, ion beam treatment and aluminum cap layer enable the depositing of stable ultra-thin silver films at 6 and 7 nm. Particularly, ion beam treatment helps to prepare a surface with better wettability toward silver, and the aluminum cap layer help to protect silver film by impeding the movement of silver surface atoms. Secondly, the film thicknesses are then used as the inputs for the simulation of the ITO/Ag/ITO sandwich structure and we found the optimum design of ITO (45 nm)/ Ag (6-7 nm)/ITO (50 nm)/ Glass. Finally, the stable silver film allows further processing of annealing at high temperatures (200C) in the vacuum and in the air, which is not possible for a stand-alone silver film. The resulting 7 nm film on glass substrate has a sheet resistance of 10 Ohm/ sq. an average transmittance in the range of 400-800 nm of 89%. This process can be implemented in other substrates as well as other transparent conductive oxides such as SnO₂, AZO, TTO, and TiO₂. Therefore, a couple of TCOs were taken into consideration for a similar sandwich structure to compare the optical performance showing potential replacements for ITO in optoelectronic applications in the circumstance that indium is getting costly.