Guanidine Nitrate (GuNO₃) as an Efficient Additive in the Electrolyte of Dye-Sensitized Solar Cells

Guanidine nitrate (GuNO₃) was introduced as an additive in I^-/I₃^--based electrolyte to investigate its photoelectrochemical effects on dye-sensitized solar cells (DSSCs). GuNO₃ induced the enhancement of the power conversion efficiency (PCE) up to ca. 21% by increasing both the photocurrent density and the open circuit voltage (V_oc) of the DSSCs relative to that without additives. Meanwhile the adsorption of guanidinium cation (Gu⁺) induced a positive shift in the conduction band edge of the TiO₂ nanoparticles (E_CB,TiO2), toward electrochemical potentials by up to ∼110 mV, the presence of NO₃^- instead of SCN^- in the electrolyte resulted in the shift in E_CB,TiO2 in the opposite direction by up to ca. 40 mV, which corresponded to an additional increase in the V_oc up to ca. 30 mV in the DSSCs with GuNO₃ relative to that with GuSCN. The use of GuNO₃ instead of GuSCN as an additive improved the PCE of DSSCs by up to ca. 6% owing to the relatively high values of V_oc and the significant increase of the fill factor (FF) by enhancement of ionic conductivity of electrolyte.