Understanding Mass Transport in Copper Electrolyte-Based Dye-Sensitized Solar Cells

Copper redox shuttles, particularly [Cu(tmby)(2)](2+/1+) (tmby = bis-(4,4',6,6'-tetramethyl-2,2'-bipyridine)), proved to be among the best electrolytes for dye-sensitized solar cells (DSCs), realizing higher power conversion efficiencies both under full sun and indoor illumination than conventional iodide/triiodide and cobalt electrolytes. Even though [Cu(tmby)(2)](2+/1+) renders a relatively higher performance, this metal complex is bulky and is limited by mass transport. Since the regeneration of the dye ground state by Cu-I and the reaction of Cu-II at the counter electrode are comparatively faster processes, the efficiency of DSC involving Cu-I/Cu-II electrolytes under relatively high light intensities is largely governed by the diffusion of Cu-I/Cu-II species. Understanding mass transport in these solar cells will enable further improvements in the performance of such copper-based DSCs. In the present stud), the role of illumination intensity on the photogenerated current and its relationship to mass transport is evaluated using the best cosensitized dye (D35:XY1) and copper electrolyte ([Cu(tmby)(2)](2+/1+) combination.