The [copper(6,6′-dimethyl-2,2′-bipyridine)2]2+/1+ ([Cu(dmbp)2]2+/1+) redox couple, which possesses a distorted tetragonal geometry of a Cu(I) complex crystal and a distorted tetrahedral coordination geometry of Cu(II) complex crystal, has been developed as a redox mediator in dye-sensitized solar cells (DSSCs). The energy of loss for dye regeneration was reduced with a very low but sufficient driving force of only 0.11 eV. A distinct increase in open-circuit voltage (VOC) was achieved and a remarkable power conversion efficiency of 10.3% was afforded at 100 mW cm−2 under AM 1.5G condition.
![Graphical abstract: Efficient dye-sensitized solar cells with [copper(6,6′-dimethyl-2,2′-bipyridine)2]2+/1+ redox shuttle](http://hg.y866.cn/compound/lib/scimg/usr/1/C6RA25676G.jpg)
