ABSTRACTAlternatives to ITO are under heavy investigation. Organic and inorganic transparent conducting materials are compared based on their transparency versus sheet resistance characteristics. Although graphene has advanced recently, TCOs are still superior in performance and can only be surpassed by the combination of transparent materials with a metal grid. Results on modeling and design optimization using a monolithically integrated CIGS cell configuration as case showed that considerable efficiency enhancement (up to 17% in power output compared to single TCOs) can be achieved for metal grid/TCO combinations. Conductivity improvement has been experimentally verified by four point probe measurements. on both commercial ITO coated PET foil as well as on ZnO coated glass with electrochemically deposited metal grids Sheet resistances as low as 0,1 Ohm/sq were reached and 80 times and 400 times conductivity improvements were obtained at a transparency loss of only 3% and 6%, respectively. It was also found that electrochemical deposition results in more conductive grids than obtained by Ag-ink screen printing due to higher aspect ratios and bulk-like conductivity of the first. Simultaneously, nanopatterning allows optimal grid width of 20 μm, as determined by modeling.
Transparent conducting materials: overview and recent results
