Supramolecular Hemicage Cobalt Mediators for Efficient and Stable Dye-Sensitized Solar Cells

摘要

A new class of dye-sensitized solar cells (DSCs) using the hemicage cobalt based mediator [Co(ttb)]^2+/3+ with the highly preorganized hexadentate ligand 5,5″,5″″-((2,4,6-triethyl benzene-1,3,5-triyl)tris(ethane-2,1-diyl))tri-2,2′-bipyridine (ttb) have been fully characterized. The performance of DSCs sensitized with organic D-π-A dyes utilizing either [Co(ttb)]^2+/3+ or the conventional [Co(bpy)3]^2+/3+ (bpy = 2,2′-bipyridine) redox mediator have comparable efficiency under 1000 Wm⁻² AM 1.5G illumination. However, the hemicage complexes exhibit exceptional stability under thermal and light stress. In particular, a 120 hour continuous light illumination stability test for DSCs using [Co(ttb)]^2+/3+ resulted in a 10% increase in performance, whereas 40% decrease in performance was found for [Co(bpy)3]^2+/3+ electrolyte based DSCs under the same conditions. The improved stability at high solar cell efficiencies demonstrates the great promise of [Co(ttb)]^2+/3+ complexes as redox mediators for efficient, cost-effective, large-scale DSC devices.