2,2′-Bipyridine – A new electrolyte additive in dye-sensitized solar cells

In this work 2,2′-bipyridine (bipy) is introduced as a new nitrogen containing electrolyte additive in Dye-sensitized solar cells (DSCs) as an alternative to the commonly used 4-tert-butylpyridine (TBP). Bipy was shown to substitute the thiocyanate ligands in the N719 ruthenium dye ~4 times slower than TBP at elevated temperatures 80–85 °C and therefore reduce the thermal degradation of N719 relative to TBP. The thermal stability experiments were performed in sealed glass ampules filled with a colloidal solution of N719 dyed TiO2 nanoparticles in an ionic liquid electrolyte with either TBP or bipy as N-additive. The glass ampules were opened after various time intervals between 0 and 2000 h of heating at either 80 or 85 °C and the N719 and its degradation
products were extracted from the TiO2 nano particles and analyzed by LC-UV/Vis-MS. After 1000 h at 85 °C in dark, 85% of N719 was intact in an electrolyte containing 0.2 M bipy whereas the same number was 67% for
TBP. DSCs prepared with bipy in the electrolyte was shown to perform equally well as DSCs with TBP containing electrolytes with light to electricity performance of 4.5% for both N-additives. 2,2′-bipyridine may therefore be
used as an alternative to TBP as N-additive in DSCs.