4. Conclusions
We systematically investigated the effects of light intensity
and operating temperature on the photovoltaic performance
of DSSCs. Firstly, a Peltier-cell-assisted
temperature control system enabled us to observe the effect
of temperature on the photovoltaic properties of DSSCs.
As a result, the PCE of DSSCs at the fixed 1-Sun condition
significantly decreased with increasing operating temperature,
which resulted in reduced liquid electrolyte viscosity
that promoted ion mobility and simultaneously accelerated
the charge recombination rate between photogenerated
electrons and liquid iodide ions. Secondly, the use of a neutral-
filter- and condenser-lens-assisted light intensity control
system enabled us to observe the effect of light
intensity in conjunction with operating temperature on
the photovoltaic performance of DSSCs. At low light
intensities (6100 mW cm2), the resulting PCE of DSSCs
significantly decreased with increasing operating temperature.
However, at high light intensities (>100 mW cm2),
the PCE of DSSCs was stably maintained due to the
increased concentration of photogenerated electrons,
which resulted in an increase in electron injection into the
TiO2 NPs and simultaneously mitigating the loss of electrons
by charge recombination. In order to maintain the
optimized photovoltaic performance of DSSCs in practical
applications, we suggest that DSSCs can be installed in
cold and sunny environments with the simultaneous use
of various effective auxiliary facilities (e.g. solar concentrator
and cooling system) for artificially controlling the light
intensity and operating temperature. We believe that our
results can significantly contribute to the development of
solar cells as viable alternative energy sources.