Grids on TCOs for higly transparent materials with a resistivity below 1 Ohm/sq

Abstract

Various transparent conducting materials are compared based on their transparency versus sheet resistance characteristics. At present, transparent conducting oxides (TCOs) are still superior in performance compared to various recent alternatives and can only be surpassed by the combination of TCOs with a metal grid. Results on modeling and design optimization are presented using a monolithically integrated CIGS cell configuration as case. This study showed that considerable efficiency enhancement (17% in power output) can be achieved for metal grid TCO combinations compared to single TCOs. Conductivity improvement has been experimentally verified on both commercial ITO PET foil as well as on ZnO coated glass with electrochemically deposited metal grids. Conductivities below 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 and more transparent grids than obtained by Ag-ink screen printing.