Modification of fluorine-doped tin oxide-electrodes by electrochemical reduction of di(4-nitrophenyl)iodonium tetrafluoroborate - And its application as a photo-anode in dye-sensitized solar cells

We report on a straightforward methodology to cover the FTO layer of the DSC photo anode with an insulating
layer of nitro phenyl groups by electrochemical reduction of di(4-nitrophenyl)-iodonium tetrafluoroborate 1.
The efficiency of the blocking layer was demonstrated by a ferrocene CV test, in which ferrocene CV peak
separations increased from 200 to 400 mV, and in which the charge transfer resistance measured by EIS increased from 600 to 20.000 Ω depending on the number of grafting CV scans. Our DSCs displayed a Voc increase
of 182 mV at 90 W/m2 corresponding to a reduction in the dark current with a factor of 1000, when using D5 as sensitizing dye, [Co(bipy)3]2+/3+ as mediator, and FTO│TiO2 as an electrode that had been grafted before by
three CV scans of 1. However, DSCs prepared with N719 and D35 as dyes and using FTO│TiO2 as photoanode grafted with 1 showed decreased performance on all cell parameters.