4 research outputs found
Enhancing Stability of Perovskite Solar Cells to Moisture by the Facile Hydrophobic Passivation
In this study, a novel and facile
passivation process for a perovskite solar cell is reported. Poor
stability in ambient atmosphere, which is the most critical demerit
of a perovskite solar cell, is overcome by a simple passivation process
using a hydrophobic polymer layer. Teflon, the hydrophobic polymer,
is deposited on the top of a perovskite solar cell by a spin-coating
method. With the hydrophobic passivation, the perovskite solar cell
shows negligible degradation after a 30 day storage in ambient atmosphere.
Suppressed degradation of the perovskite film is proved in various
ways: X-ray diffraction, light absorption spectrum, and quartz crystal
microbalance. This simple but effective passivation process suggests
new kind of approach to enhance stability of perovskite solar cells
to moisture
Unbiased Sunlight-Driven Artificial Photosynthesis of Carbon Monoxide from CO<sub>2</sub> Using a ZnTe-Based Photocathode and a Perovskite Solar Cell in Tandem
Solar
fuel production, mimicking natural photosynthesis of converting
CO<sub>2</sub> into useful fuels and storing solar energy as chemical
energy, has received great attention in recent years. Practical large-scale
fuel production needs a unique device capable of CO<sub>2</sub> reduction
using only solar energy and water as an electron source. Here we report
such a system composed of a gold-decorated triple-layered ZnO@ZnTe@CdTe
core–shell nanorod array photocathode and a CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell in tandem. The assembly
allows effective light harvesting of higher energy photons (>2.14
eV) from the front-side photocathode and lower energy photons (>1.5
eV) from the back-side-positioned perovskite solar cell in a single-photon
excitation. This system represents an example of a photocathode–photovoltaic
tandem device operating under sunlight without external bias for selective
CO<sub>2</sub> conversion. It exhibited a steady solar-to-CO conversion
efficiency over 0.35% and a solar-to-fuel conversion efficiency exceeding
0.43% including H<sub>2</sub> as a minor product
Solution-Processed Ultrathin TiO<sub>2</sub> Compact Layer Hybridized with Mesoporous TiO<sub>2</sub> for High-Performance Perovskite Solar Cells
The electron transport layer (ETL)
is a key component of perovskite
solar cells (PSCs) and must provide efficient electron extraction
and collection while minimizing the charge recombination at interfaces
in order to ensure high performance. Conventional bilayered TiO<sub>2</sub> ETLs fabricated by depositing compact TiO<sub>2</sub> (c-TiO<sub>2</sub>) and mesoporous TiO<sub>2</sub> (mp-TiO<sub>2</sub>) in sequence
exhibit resistive losses due to the contact resistance at the c-TiO<sub>2</sub>/mp-TiO<sub>2</sub> interface and the series resistance arising
from the intrinsically low conductivity of TiO<sub>2</sub>. Herein,
to minimize such resistive losses, we developed a novel ETL consisting
of an ultrathin c-TiO<sub>2</sub> layer hybridized with mp-TiO<sub>2</sub>, which is fabricated by performing one-step spin-coating
of a mp-TiO<sub>2</sub> solution containing a small amount of titanium
diisopropoxide bisÂ(acetylacetonate) (TAA). By using electron microscopies
and elemental mapping analysis, we establish that the optimal concentration
of TAA produces an ultrathin blocking layer with a thickness of ∼3
nm and ensures that the mp-TiO<sub>2</sub> layer has a suitable porosity
for efficient perovskite infiltration. We compare PSCs based on mesoscopic
ETLs with and without compact layers to determine the role of the
hole-blocking layer in their performances. The hybrid ETLs exhibit
enhanced electron extraction and reduced charge recombination, resulting
in better photovoltaic performances and reduced hysteresis of PSCs
compared to those with conventional bilayered ETLs
Soft-Template Simple Synthesis of Ordered Mesoporous Titanium Nitride-Carbon Nanocomposite for High Performance Dye-Sensitized Solar Cell Counter Electrodes
Ordered mesoporous titanium nitride-carbon (denoted as
OM TiN-C)
nanocomposite with high surface area (389 m<sup>2</sup> g<sup>–1</sup>) and uniform hexagonal mesopores (ca. 5.5 nm) was facilely synthesized
via the soft-template method. As a structure-directing agent, Pluronic
F127 triblock copolymer formed an ordered structure with inorganic
precursors, resol polymer, and prehydrolyzed TiCl<sub>4</sub>, followed
by a successive heating at 700 °C under nitrogen and ammonia
flow. In this study, the amorphous carbon within the parent OM TiO<sub>2</sub>-C acted as a rigid support, preventing structural collapse
during the conversion process of TiO<sub>2</sub> nanocrystals to TiN
nanocrystals. The OM TiN-C was then successfully applied as counter
electrode material in dye-sensitized solar cells (DSCs). The organic
electrolyte disulfide/thiolate (T<sub>2</sub>/T<sup>–</sup>) was introduced to study the electrocatalytic property of the OM
TiN-C nanocomposite. Because of the existence of TiN nanocrystals
and the defect sites of the amorphous carbon, the DSCs using OM TiN-C
as a counter electrode showed 6.71% energy conversion efficiency (platinum
counter electrode DSCs: 3.32%) in the organic electrolyte system (T<sub>2</sub>/T<sup>–</sup>). Furthermore, the OM TiN-C counter
electrode based DSCs showed an energy conversion efficiency of 8.41%,
whereas the DSCs using platinum as a counter electrode showed a conversion
efficiency of only 8.0% in an iodide electrolyte system. The superior
performance of OM TiN-C counter electrode resulted from the low charge
transfer resistance, enhanced electrical conductivity, and abundance
of active sites of the OM TiN-C nanocomposite. Moreover, OM TiN-C
counter electrode showed better chemical stability in organic electrolyte
compared with the platinum counter electrode