4 research outputs found
Enhanced Photocurrent of Transparent CuFeO<sub>2</sub> Photocathodes by Self-Light-Harvesting Architecture
Efficient
sunlight-driven water-splitting devices can be achieved by using an
optically and energetically well-matched pair of photoelectrodes in
a tandem configuration. The key for maximizing the photoelectrochemical
efficiency is the use of a highly transparent front photoelectrode
with a band gap below 2.0 eV. Herein, we propose two-dimensional (2D)
photonic crystal (PC) structures consisting of a CuFeO<sub>2</sub>-decorated microsphere monolayer, which serve as self-light-harvesting
architectures allowing for amplified light absorption and high transparency.
The photocurrent densities are evaluated for three CuFeO<sub>2</sub> 2D PC-based photoelectrodes with microspheres of different sizes.
The optical analysis confirmed the presence of a photonic stop band
that generates <i>slow light</i> and at the same time amplifies
the absorption of light. The 410 nm sized CuFeO<sub>2</sub>-decorated
microsphere 2D PC photocathode shows an exceptionally high visible
light transmittance of 76.4% and a relatively high photocurrent of
0.2 mA cm<sup>–2</sup> at 0.6 V vs a reversible hydrogen electrode.
The effect of the microsphere size on the carrier collection efficiency
was analyzed by in situ conductive atomic force microscopy observation
under illumination. Our novel synthetic method to produce self-light-harvesting
nanostructures provides a promising approach for the effective use
of solar energy by highly transparent photocathodes
Molecular Chemistry-Controlled Hybrid Ink-Derived Efficient Cu<sub>2</sub>ZnSnS<sub>4</sub> Photocathodes for Photoelectrochemical Water Splitting
To realize economically competitive
hydrogen production through
photoelectrochemical (PEC) water splitting, it is essential to develop
an efficient photoelectrode consisting of earth-abundant constituents
in conjunction with low-cost solution processing. Cu<sub>2</sub>ZnSnS<sub>4</sub> (CZTS) has received significant attention as a promising
photocathode owing to its abundance and good absorption properties.
However, the efficiency of the solution-processed CZTS photocathode
is not yet comparable to its counterparts. Here, a hybrid ink, obtained
by careful control of precursor mixing order, was used to produce
a highly efficient CZTS photocathode. The molecular chemistry-controlled
hybrid ink formulation, particularly the roles of thiourea–Sn<sup>2+</sup> complexation, was elucidated by liquid Raman spectroscopy.
The hybrid ink-derived CZTS thin films modified with conformal coating
of an n-type TiO<sub>2</sub>/CdS double layer and a Pt electrocatalyst
achieved an exceptionally high photocurrent of 13 mA cm<sup>–2</sup> at −0.2 V versus a reversible hydrogen electrode
under 1 sun illumination. The modified photocathodes showed relatively
stable H<sub>2</sub> production with faradaic efficiency close to
unity
Retarding Crystallization during Facile Single Coating of NaCl-Incorporated Precursor Solution for Efficient Large-Area Uniform Perovskite Solar Cells
We demonstrated crystallization
retardation of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> thin film
during single coating of precursor solution by simple addition of
NaCl. NaCl was codissolved into a precursor mixture solution containing
PbI<sub>2</sub> and methylammonium iodide (MAI). Dissolved NaCl interacted
with the PbI<sub>2</sub> in solution and produced a stable intermediate
phase, which was converted to a full-coverage uniform perovskite absorber
layer via reaction with MAI during a single spin-coating. The resulting
planar-structure perovskite solar cell made from NaCl-supplemented
precursor solution showed a 48% improvement in power conversion efficiency
(PCE) (maximum value 15.16%) over the device fabricated without the
additive. Our NaCl-supplemented single coating represents an easy
approach to effectively obtain highly reproducible uniform performance
at an overall position in 5 cm × 5 cm sized cells (divided into
20 subcells with an active area of 0.06 cm<sup>2</sup>) with average
PCEs of 12.00 ± 0.48%
Investigating Recombination and Charge Carrier Dynamics in a One-Dimensional Nanopillared Perovskite Absorber
Organometal
halide perovskite materials have become an exciting
research topic as manifested by intense development of thin film solar
cells. Although high-performance solar-cell-based planar and mesoscopic
configurations have been reported, one-dimensional (1-D) nanostructured
perovskite solar cells are rarely investigated despite their expected
promising optoelectrical properties, such as enhanced charge transport/extraction.
Herein, we have analyzed the 1-D nanostructure effects of organometal
halide perovskite (CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3–<i>x</i></sub>Cl<sub><i>x</i></sub>) on recombination
and charge carrier dynamics by utilizing a nanoporous anodized alumina
oxide scaffold to fabricate a vertically aligned 1-D nanopillared
array with controllable diameters. It was observed that the 1-D perovskite
exhibits faster charge transport/extraction characteristics, lower
defect density, and lower bulk resistance than the planar counterpart.
As the aspect ratio increases in the 1-D structures, in addition,
the charge transport/extraction rate is enhanced and the resistance
further decreases. However, when the aspect ratio reaches 6.67 (diameter
∼30 nm), the recombination rate is aggravated due to high interface-to-volume
ratio-induced defect generation. To obtain the full benefits of 1-D
perovskite nanostructuring, our study provides a design rule to choose
the appropriate aspect ratio of 1-D perovskite structures for improved
photovoltaic and other optoelectrical applications