L. Dloczik et al., DYNAMIC-RESPONSE OF DYE-SENSITIZED NANOCRYSTALLINE SOLAR-CELLS - CHARACTERIZATION BY INTENSITY-MODULATED PHOTOCURRENT SPECTROSCOPY, JOURNAL OF PHYSICAL CHEMISTRY B, 101(49), 1997, pp. 10281-10289
The frequency-dependent photocurrent response of dye-sensitized TiO2 c
ells to modulated illumination is analyzed. Analytical expressions are
derived that describe generation, collection, and recombination of el
ectrons in a thin layer nanocrystalline solar cell under conditions of
steady illumination and with a superimposed small amplitude modulatio
n. The analysis considers illumination from the contact side and from
the counter electrode side, and characteristic differences in the inte
nsity-modulated photocurrent response are predicted for the two cases.
The attenuation of the ac photocurrent by the RC time constant of the
cell is also considered. The theoretical analysis shows that intensit
y modulated photocurrent spectroscopy (IMPS) can provide new insight i
nto the dynamics of electron transport and collection in the dye-sensi
tized solar cell. Experimental IMPS data measured for high-efficiency
dye-sensitized cells are fitted to the theoretical model using Bode pl
ots in order to derive values of the lifetime (2 x 10(-2) s) and diffu
sion coefficient (5 x 10(-5) cm(2) s(-1)) of photoinjected electrons.