We report a new water soluble and stable thiolate/disulfide redox couple (T(-)/DS) and its use with a new zwitterionic and thiocyanate-free dye (T169) in a 100% aqueous electrolyte system. A DSSC incorporating T169 and the T(-)/DS showed the highest photocurrents (Jsc = 13.30 mA cm(-2)) and IPCE% (84%) values reported to date. In addition, a 2000 h long-term stability measurement was performed, where Jsc and Voc of the above mentioned DSSC stayed somehow the same except for the fill factor (FF) which decreased from 0.62 to 0.48 and consequently lowered the total efficiency (from η = 4.5% on day 1 to η = 3.3% after 2000 h).