As can be seen from Table 4, efficiency loss of DSSCs
decreased with a decreasing pH from 17.3% to 5.7%, after
being exposed to the simulated sunlight for 3 h. A reason
for the better efficiency and stability is that, at pH below 2,
anthocyanin existed as flavylium ion, which is stable form
of anthocyanin, an increasing pH hydrated this ion to
quinonoidal bases. These compounds are labile and can be
transformed into the colorless carbinol pseudobase and
chalcone [18]. It was evident that at low pH the formation
of flavylium ion form is favorable [18]. However, the cell
deterioration by acid leaching is expected as the pH goes
lower (pH o 1), which results in a lower efficienc