Our results
demonstrate the potential of mesoporous SiO2 in improving the
device efficiency in an efficient manner. In order to investigate,
the reasons for the device improvement, we first analysed estimated
photovoltaic parameters. As shown in the figures, the open
circuit voltage (Voc) remains almost unaffected while the short
circuit current density (Jsc) increases gradually with increase in
wt% of mesoporous SiO2. The improvement in JSC is attributable
to enhanced light harvesting on account of incorporation of mesoporous
SiO2. However, FF is maximum upon incorporation of
0.75 wt% of mesoporous SiO2 and this improvement is attributable
to the blocking effect of SiO2. Incorporation of mesoporous SiO2
more than 0.75 wt% results in reduced fill factor, which may be
due to the resistance posed by insulating SiO2. This is also evident
from the dark J–V characteristics of DSSCs which shows increment
in the value of onset potential upon incorporation of mesoporous
SiO2 up to 0.75 wt% and decreases upon further incorporation of
mesoporous SiO2 (Fig. 5(e)). Therefore, the overall highest
efficiency (3.57%) is obtained for 0.75 wt% of mesoporous SiO2
which is an improvement of 50% over the reference cell.