4 research outputs found
p-Type Dye-Sensitized Solar Cells Based on Delafossite CuGaO<sub>2</sub> Nanoplates with Saturation Photovoltages Exceeding 460 mV
Exploring new p-type semiconductor nanoparticles alternative to
the commonly used NiO is crucial for p-type dye-sensitized solar cells
(p-DSSCs) to achieve higher open-circuit voltages (<i>V</i><sub>oc</sub>). Here we report the first application of delafossite
CuGaO<sub>2</sub> nanoplates for p-DSSCs with high photovoltages.
In contrast to the dark color of NiO, our CuGaO<sub>2</sub> nanoplates
are white. Therefore, the porous films made of these nanoplates barely
compete with the dye sensitizers for visible light absorption. This
presents an attractive advantage over the NiO films commonly used
in p-DSSCs. We have measured the dependence of <i>V</i><sub>oc</sub> on the illumination intensity to estimate the maximum obtainable <i>V</i><sub>oc</sub> from the CuGaO<sub>2</sub>-based p-DSSCs.
Excitingly, a saturation photovoltage of 464 mV has been observed
when a polypyridyl Co<sup>3+/2+</sup>(dtb-bpy) electrolyte was used.
Under 1 Sun AM 1.5 illumination, a <i>V</i><sub>oc</sub> of 357 mV has been achieved. These are among the highest values
that have been reported for p-DSSCs
p-Type Dye-Sensitized Solar Cells Based on Delafossite CuGaO<sub>2</sub> Nanoplates with Saturation Photovoltages Exceeding 460 mV
Exploring new p-type semiconductor nanoparticles alternative to
the commonly used NiO is crucial for p-type dye-sensitized solar cells
(p-DSSCs) to achieve higher open-circuit voltages (<i>V</i><sub>oc</sub>). Here we report the first application of delafossite
CuGaO<sub>2</sub> nanoplates for p-DSSCs with high photovoltages.
In contrast to the dark color of NiO, our CuGaO<sub>2</sub> nanoplates
are white. Therefore, the porous films made of these nanoplates barely
compete with the dye sensitizers for visible light absorption. This
presents an attractive advantage over the NiO films commonly used
in p-DSSCs. We have measured the dependence of <i>V</i><sub>oc</sub> on the illumination intensity to estimate the maximum obtainable <i>V</i><sub>oc</sub> from the CuGaO<sub>2</sub>-based p-DSSCs.
Excitingly, a saturation photovoltage of 464 mV has been observed
when a polypyridyl Co<sup>3+/2+</sup>(dtb-bpy) electrolyte was used.
Under 1 Sun AM 1.5 illumination, a <i>V</i><sub>oc</sub> of 357 mV has been achieved. These are among the highest values
that have been reported for p-DSSCs
Probing the Low Fill Factor of NiO pāType Dye-Sensitized Solar Cells
p-Type dye-sensitized solar cells (<i>p</i>-DSCs) have
attracted increasing attention recently, but they suffer from low
fill factors (FFs) and unsatisfactory efficiencies. A full comprehension
of the hole transport and recombination processes in the NiO <i>p</i>-DSC is of paramount importance for both the fundamental
study and the practical device optimization. In this article, NiO <i>p</i>-DSCs were systematically probed under various bias and
illumination conditions using electrochemical impedance spectroscopy
(EIS), intensity modulated photocurrent spectroscopy (IMPS), and intensity
modulated photovoltage spectroscopy (IMVS). Under the constant 1 sun
illumination, the recombination resistance (<i>R</i><sub>rec</sub>) of the cell deviates from an exponential relationship
with the potential and saturates at ā¼130 Ī© cm<sup>2</sup> under the short circuit condition, which is ascribed to the overwhelming
recombination with the reduced dye anions. Such a small <i>R</i><sub>rec</sub> results in the small dc resistance, which decreases
the āflatnessā of the <i>JāV</i> curve.
The quantitative analysis demonstrates that the FF value is largely
attenuated by the recombination of holes in NiO with the reduced dyes.
Our analysis also shows that if this recombination can be eliminated,
then an FF value of 0.6 can be reached, which agrees with the theoretical
calculation with a <i>V</i><sub>oc</sub> of 160 mV
Synthesis, Photophysics, and Photovoltaic Studies of Ruthenium Cyclometalated Complexes as Sensitizers for pāType NiO Dye-Sensitized Solar Cells
We report the first application of cyclometalated ruthenium
complexes
of the type RuĀ[(N<sup>ā§</sup>N)<sub>2</sub>(C<sup>ā§</sup>N)]<sup>+</sup> as sensitizers for p-type NiO dye-sensitized solar
cells (NiO p-DSCs). These dyes exhibit broad absorption in the visible
region. The carboxylic anchoring group is attached to the phenylpyridine
ligand, which results in efficient hole injection. Moreover, the distance
between the RuĀ[(N<sup>ā§</sup>N)<sub>2</sub>(C<sup>ā§</sup>N)]<sup>+</sup> core and the carboxylic anchoring group is systematically
varied by inserting rigid phenylene linkers. Femtosecond transient
absorption (TA) studies reveal that the interfacial charge recombination
rate between reduced sensitizers and holes in the valence band of
NiO decreases as the number of phenylene linkers increases across
the series. As a result, the solar cell made of the dye with the longest
spacer (O12) exhibits the highest efficiency with both increased short-circuit
current (<i>J</i><sub>sc</sub>) and open-circuit voltage
(<i>V</i><sub>oc</sub>). The incident photon-to-current
conversion efficiency (IPCE) spectra match well with the absorption
spectra of sensitizers, suggesting the observed cathodic current is
generated from the dye sensitization. In addition, the absorbed photon-to-current
conversion efficiencies (APCEs) display an increment across the series.
We further studied the interfacial charge recombination of our solar
cells by electrochemical impedance spectroscopy (EIS). The results
reveal an enhanced hole lifetime as the number of phenylene linkers
increases. This study opens up opportunities of using cyclometalated
Ru complexes for p-DSCs