The transport and recombination of electrons in dye-sensitized TiO(2) solar cells were studied by analysis of the current and voltage response to a small square-wave light-intensity modulation. Solar cells were studied under working conditions by using potentiostatic and galvanostatic conditions. An increase in applied voltage, that is, from 0 V toward open-circuit voltage, was found to lead to faster electron transport at low light intensities, while it slowed transport at higher light intensities. This observation seems to be conflicting with the multiple trapping model with diffusive transport. An effective diffusion length at the maximum power point was calculated, and it was shown that it decreases with increasing light intensity.
Five ionic liquids (ILs) of the general formula Im+A-, where Im+ = 1-methyl-3-n-butyl-imidazolium, A- =
I- (1), BF4
- (2), SCN- (3), CF3CO2
- (4), and CF3SO3
- (5), were used in electrolytes for dye-sensitized
monolithic solar cells. The properties of the electrolytes and various characteristics of the solar cell performance,
such as electron transport and electron lifetime, were studied. The composition of the binary electrolytes, i.e.,
the different anions, have a significant effect on the viscosity, but only a modest effect of the measured
diffusion coefficient for triiodide. No significant effect of the electrolyte composition on the electron transport
time in the mesoporous TiO2 film was found, while there was a pronounced effect on the electron lifetime.
Monolithic solar cells with thiocyanate, IL 3, showed overall light-to-electricity conversion efficiency up to
5.6% in 250 W m-2 simulated sunlight and have promising stability.
Page 17715. In our recently published Letter, the effect of RC attenuation was not correctly taken into account. This led to a misinterpretation of the photocurrent response data shown in Figure 3a and further discussion.Under operating conditions, electrons are accumulated throughout the nanostructured TiO 2 , rendering the film conducting. The photocurrent response under such conditions is affected or dominated by the RC time of the solar cell, where the resistance R is the sum of the resistances of the conducting glass and that of the TiO 2 film, and the capacitance C the sum of the capacity of the conducting glass/electrolyte interface and the chemical capacitance of the nanostructured TiO 2 . Figure 3b (given here) shows the transport time calculated from the data of Figure 3a using appropriate correction for the RC time. At lower light intensities transport time decreased with voltage, whereas little change was observed at the highest light intensity. At voltages higher than 0.65 V transport times were independent of light intensity. Table 2 (given here) shows calculated effective diffusion coefficients and diffusion lengths using the corrected values of τ tr . We thank Dr. B. C. O'Regan, Imperial College London, for rapidly pointing out our error and we would like to refer to his recent paper 1 that deals with similar issues.
References and Notes(1) O'Regan, B. C.; Bakker, K.; Kroeze, J.; Smit, H.; Sommeling, P.; Durrant, J. R.
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