Metallic grids for low resistive transparent conductors: Modeling and experiments

At present, transparent conducting oxides (TCOs) are still superior in performance to most other transparent conductors. Results on opto-electronic modeling and design optimization of TCOs are presented using a monolithically integrated CIGS cell configuration as case. For various cell dimensions and TCO characteristics, the cell output was determined for both bare TCOs and TCOs with a metallic grid. This study shows that considerable efficiency enhancement (17% in power output) can be achieved for metal grid TCO combinations compared to TCO only. Conductivity improvement has been experimentally verified on both commercial ITO PET foil as well as on ZnO:Al coated glass with electrochemically deposited metal grids. Conductivities below 0,1 Ω/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 lower surface area covering grids than obtained by Ag-ink screen printing.