Non‐Corrosive, Non‐Absorbing Organic Redox Couple for Dye‐Sensitized Solar Cells

A new colorless electrolyte containing an organic redox couple, tetramethylthiourea (TMTU) and its oxidized dimer tetramethylformaminium disulfide dication ([TMFDS] 2+ ), is applied to dye‐sensitized solar cells (DSCs). Advantages of this redox couple include its non‐corrosive nature, low cost, and easy handling. More impressively, it operates well with carbon electrodes. The DSCs fabricated with a lab‐made HCS‐CB carbon counter‐electrode can present up to 3.1% power conversion efficiency under AM 1.5 illumination of 100 mW·cm −2 and 4.5% under weaker light intensities. This result distinctly outperforms the identical DSCs with a Pt electrode. Corrosive experiments reveal that Al and stainless steel (SS) sheets are stable in the [TMFDS] 2+ /TMTU‐based electrolyte. Its electrochemical impedance spectrum (EIS) is used to evaluate the influence of different counter‐electrodes on the cell performance, and preliminary investigations reveal that carbon electrodes with large surface areas and ideal corrosion‐inertness toward the sulfur‐containing [TMFDS] 2+ /TMTU redox couple exhibit promise for application in iodine‐free DSCs.