3. Results and discussion
In order to examine the effect of operating temperature
on the photovoltaic performance of the DSSCs, we varied
the operating temperature of the DSSCs using a Peltier cell
under the fixed 1-Sun irradiance condition (i.e. AM 1.5 &
100 mW cm2). From the values listed in Table 1 and
Fig. 3a, we can clearly observe that the short-circuit current
density (Jsc) and open-circuit voltage (Voc) decrease with an
increase in cell temperature. Both the Jsc and Voc values of
the DSSCs decrease from 14.78 mA cm2 and 0.75 V at
T = 4 C to 13.56 mA cm2 and 0.64 V at T = 60 C,
respectively, thereby resulting in a considerable reduction
in the corresponding PCE value from 7.25% at
T = 4 C to 5.67% at T = 60 C, respectively.
In order to determine the possible reasons for these
observed phenomena, we performed an electrochemical
impedance spectroscope (EIS) measurement for the DSSCs
operated at different temperatures. Further, from Table 1
and Fig. 3b, we note that the calculated electron lifetime
(se = [2pfmax]1, where fmax denotes the maximum frequency)
slightly reduces with increasing operating temperature,
thereby suggesting that the photogenerated electrons
diffuse further at lower temperatures. From the Nyquist
plots (Fig. 3c) and the corresponding analyzed elemental
resistance (Fig. 3d), we observe that the charge transfer
resistance gradually reduces with increasing operating tem-