The present invention relates to electrolyte formulations comprising at least one compound of formula (I) Ma+[B(Rf)(CN)x(F)y]a— (I) in which Ma+ is an inorganic or organic cation, Rf denotes straight-chain or branched perfluoroalkyl groups having 1 to 4 C atoms, C6F5, C6H5, partially fluorinated phenyl or phenyl which is monosubstituted or disubstituted by perfluoroalkyl groups having 1 to 4 C atoms, a is 1 or 2, x is 1, 2 or 3, y is 0, 1 or 2 and x+y is 3 and their use in an electrochemical and/or optoelectronic device such as a photovoltaic cell, a capacitor, a light emitting device, an electrochromic or photo-electrochromic device, an electrochemical sensor and/or biosensor, preferably their use in a dye or quantum dot sensitized solar cell.