We have demonstrated the generation of photovoltaic currents
upon the illumination of FTO electrodes coated with TiO2 nanocrystals
and sensitized with the pigments carotenoid and anthocyanin,
which were extracted from the flowers of K. japonica and
R. chinensis, respectively, using a simple extraction technique.
The peaks at 1080 and 1646 cm1 for the carotenoid molecule
are attributed to the symmetric vibrational modes of the C–C and
C@C stretching. The partial appearance of the quinonoidal form
of the anthocyanin molecule is confirmed by the peak at
1726 cm1, which corresponds to the C@O stretching vibration.
The broad absorption peak of both the pigments in the visible
range indicates the adsorption of dye molecules to the TiO2 nanoparticles.
The addition of sugar molecules to the carotenoid pigment
enhanced the short-circuit current from 0.559 to
0.750 (mA/cm2) and the fill factor from 0.677 to 0.705, whereas
the addition of sugar molecules to the anthocyanin pigment suppressed
the current density, and thereby caused a decrease in efficiency.
Although the fill factors for the extracted pigments
remained high, the current conversion efficiencies were very low
for both K. japonica and R. chinensis compared to N719 dye. The
efficiency could be improved further by the addition of different
stabilizing agents or binders to the pigments in which the research
is under progress. The simple extraction procedure, low cost, wide
availability, and environmentally friendly nature make such natural
dyes promising alternative sources of sensitizers for DSSCs.