The research of employing polyoxometalates as pure-inorganic electron-transfer mediators on dye-sensitized solar cells

•This is the first report of a pure-inorganic-cobalt-compound redox couple for DSSCs.•Two Keggin-type POMs have been employed as a redox couple in DSSCs.•The redox potential of the {CoII/IIIW12} couple matches with dye and TiO2.•The {CoII/IIIW12} redox couple shows weak absorption in the visible light region.

Two Keggin-type polyoxometalates [K6CoIIW12O40 (denoted as {CoIIW12}) and K5CoIIIW12O40 (denoted as {CoIIIW12})] were firstly employed as the redox couple in dye-sensitized solar cells. Photocurrent density–photovoltage curves, cyclic voltammetry curves, photocurrent action spectra and UV–vis spectra demonstrated that {CoIIW12} and {CoIIIW12} displayed weak absorption in the visible light region, potential matching with dye and TiO2 conducting band, and significant conversion efficiency.

Graphical abstractTwo Keggin-type polyoxometalates have been successfully employed as the redox couple in dye-sensitized solar cells for the first time, which achieved relatively high values of open circuit voltage (651 mV) and fill factor (0.549).Figure optionsDownload full-size imageDownload as PowerPoint slide