3 research outputs found
Universal Features of Electron Dynamics in Solar Cells with TiO<sub>2</sub> Contact: From Dye Solar Cells to Perovskite Solar Cells
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
Universal Features of Electron Dynamics in Solar Cells with TiO<sub>2</sub> Contact: From Dye Solar Cells to Perovskite Solar Cells
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
Origin and Whereabouts of Recombination in Perovskite Solar Cells
The
success of metal halide perovskite solar cells stems from high
absorption combined with a low recombination rate. Despite the fact
these properties are inherent to the perovskite material, the choice
of selective contacts is critical to achieve high voltages according
to experimental evidence. In this work, the impedance and the open-circuit
photopotential are measured for two excitation wavelengths (blue and
red light), in two illumination directions (back and front), and at
different temperatures. The open-circuit recombination characteristics
of two different perovskite compositions, i.e., pure MAPbI<sub>3</sub> and mixed ion-based (FAPbI<sub>3</sub>)<sub>0.85</sub>(MABr<sub>3</sub>)<sub>0.15</sub>, and with two different hole selective layers
(Spiro-OMeTAD and P3HT) have been studied. Our results indicate that,
for the studied devices, the recombination process that determines
the open-circuit potential is governed by the bulk of the perovskite
layer via a trap-limited mechanism, but surface-mediated recombination
cannot be ruled out for P3HT contact or degraded devices. Further,
we propose a model that provides a general interpretation of the nature
of recombination in perovskite solar cells