A fluorine-doped SnO2 conducting glass (FTO; sheet resistance
10 X sq.1
; obtained from BHEL, India) was cleaned with double
distilled water and acetone. The TiO2 thin film on FTO glass as
the photo anode was prepared with the active area of 1 1 cm2
according to the procedure described elsewhere [18]. Surface morphology
of the deposited TiO2 film was studied by scanning electron
microscope (SEM) (Hitachi S-3400N) and atomic force
microscopy (AFM) (Bruker Veeco, multimode-8) operated in tapping
mode. Conducting glass coated with chemically deposited
platinum from 0.05 M hexachloroplatinic acid (H2PtCl6) in isopropanol
was used as a counter electrode [19].
The TiO2 film coated on FTO glass was heated at 450 C for
30 min in a tubular furnace [18]. After cooling TiO2 thin film at
80 C, the film was soaked in dye solutions for 24 h at room temperature
for the dye to adsorb properly on the TiO2 surface and
to avoid the rehydration of TiO2 film. After being rinsed with ethanol,
the photo anode was placed on top of the counter electrode
and tightly clipped together to form a cell. An electrolyte was then
injected into the space between two electrodes. The electrolyte is
composed of 0.5 M lithium iodide (LiI), 0.05 M iodine (I2), and
0.5 M 4-tert-butylpyridine (TBP) dissolved in 2-methoxypropionitrile.
The standard cell using cis-bis(isothiocyanato)bis(2,20
-bipyridyl-4,40
-dicarboxylato)-ruthenium(II) (N3 dye) as the sensitizer
was fabricated similarly for comparison with the DSSCs fabricated
with the extracts of fruits of ivy gourd and flowers of red
frangipani.
The solar to electric energy conversion efficiencies were measured
under simulated solar light at 100 mW cm2
. The photocurrent–voltage
characteristics of the DSSCs were recorded with
potentiostat/galvanostat (Autolab-84610).
Res