Universal Features of Electron Dynamics in Solar Cells
with TiO<sub>2</sub> Contact: From Dye Solar Cells to Perovskite Solar
Cells
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Abstract
The
electron dynamics of solar cells with mesoporous TiO<sub>2</sub> contact
is studied by electrochemical small-perturbation techniques.
The study involved dye solar cells (DSC), solid-state perovskite solar
cells (SSPSC), and devices where the perovskite acts as sensitizer
in a liquid-junction device. Using a transport-recombination continuity
equation we found that mid-frequency time constants are proper lifetimes
that determine the current–voltage curve. This is not the case
for the SSPSC, where a lifetime of ∼1 μs, 1 order of
magnitude longer, is required to reproduce the current–voltage
curve. This mismatch is attributed to the dielectric response on the
mid-frequency component. Correcting for this effect, lifetimes lie
on a common exponential trend with respect to open-circuit voltage.
Electron transport times share a common trend line too. This universal
behavior of lifetimes and transport times suggests that the main difference
between the cells is the power to populate the mesoporous TiO<sub>2</sub> contact with electrons