4 research outputs found
Extraction of Absorption and Scattering Contribution of Metallic Nanoparticles Toward Rational Synthesis and Application
Noble metal nanoparticles have unique
localized surface plasmon
resonance (LSPR), leading to their strong absorption and scattering
in the visible light range. Up to date, the common practice in the
selection of nanoparticles for a specific application is still based
on the measured extinction spectra. This practice may be erroneous,
because the extinction spectra contain both absorption and scattering
contribution that may play different roles in different applications.
It would be highly desirable to develop an efficient way to obtain
the absorption and scattering spectra simultaneously. Herein, we develop
a method to use the experimentally measured extinction and scattering
signals to extract the absorption and scattering spectra that is in
excellent agreement with that simulated by discrete dipole approximation
(DDA). The heating curve measurement on the three types of gold nanorods,
with almost the same extinction spectra but different absorption and
scattering contribution, convincingly reveals an excellent correlation
between the heating effect and the absorption strength rather than
the extinction strength. The result demonstrates the importance to
obtain the scattering and absorption spectra to predict the potential
application for different types of nanoparticles, which in turn will
screen efficiently nanoparticles for a specific application
Understanding the Cubic Phase Stabilization and Crystallization Kinetics in Mixed Cations and Halides Perovskite Single Crystals
The
spontaneous α-to-δ phase transition of the formamidinium-based
(FA) lead halide perovskite hinders its large scale application in
solar cells. Though this phase transition can be inhibited by alloying
with methylammonium-based (MA) perovskite, the underlying mechanism
is largely unexplored. In this Communication, we grow high-quality
mixed cations and halides perovskite single crystals (FAPbI<sub>3</sub>)<sub>1–<i>x</i></sub>(MAPbBr<sub>3</sub>)<sub><i>x</i></sub> to understand the principles for maintaining pure
perovskite phase, which is essential to device optimization. We demonstrate
that the best composition for a perfect α-phase perovskite without
segregation is <i>x</i> = 0.1–0.15, and such a mixed
perovskite exhibits carrier lifetime as long as 11.0 μs, which
is over 20 times of that of FAPbI<sub>3</sub> single crystal. Powder
XRD, single crystal XRD and FT-IR results reveal that the incorporation
of MA<sup>+</sup> is critical for tuning the effective Goldschmidt
tolerance factor toward the ideal value of 1 and lowering the Gibbs
free energy via unit cell contraction and cation disorder. Moreover,
we find that Br incorporation can effectively control the perovskite
crystallization kinetics and reduce defect density to acquire high-quality
single crystals with significant inhibition of δ-phase. These
findings benefit the understanding of α-phase stabilization
behavior, and have led to fabrication of perovskite solar cells with
highest efficiency of 19.9% via solvent management
Understanding the Cubic Phase Stabilization and Crystallization Kinetics in Mixed Cations and Halides Perovskite Single Crystals
The
spontaneous α-to-δ phase transition of the formamidinium-based
(FA) lead halide perovskite hinders its large scale application in
solar cells. Though this phase transition can be inhibited by alloying
with methylammonium-based (MA) perovskite, the underlying mechanism
is largely unexplored. In this Communication, we grow high-quality
mixed cations and halides perovskite single crystals (FAPbI<sub>3</sub>)<sub>1–<i>x</i></sub>(MAPbBr<sub>3</sub>)<sub><i>x</i></sub> to understand the principles for maintaining pure
perovskite phase, which is essential to device optimization. We demonstrate
that the best composition for a perfect α-phase perovskite without
segregation is <i>x</i> = 0.1–0.15, and such a mixed
perovskite exhibits carrier lifetime as long as 11.0 μs, which
is over 20 times of that of FAPbI<sub>3</sub> single crystal. Powder
XRD, single crystal XRD and FT-IR results reveal that the incorporation
of MA<sup>+</sup> is critical for tuning the effective Goldschmidt
tolerance factor toward the ideal value of 1 and lowering the Gibbs
free energy via unit cell contraction and cation disorder. Moreover,
we find that Br incorporation can effectively control the perovskite
crystallization kinetics and reduce defect density to acquire high-quality
single crystals with significant inhibition of δ-phase. These
findings benefit the understanding of α-phase stabilization
behavior, and have led to fabrication of perovskite solar cells with
highest efficiency of 19.9% via solvent management
Recommended from our members
Constructing Two-Dimensional Nanoparticle Arrays on Layered Materials Inspired by Atomic Epitaxial Growth
Constructing
nanoparticles into well-defined structures at mesoscale
and larger to create novel functional materials remains a challenge.
Inspired by atomic epitaxial growth, we propose an “epitaxial
assembly” method to form two-dimensional nanoparticle arrays
(2D NAs) directly onto desired materials. As an illustration, we employ
a series of surfactant-capped nanoparticles as the “artificial
atoms” and layered hybrid perovskite (LHP) materials as the
substrates and obtain 2D NAs in a large area with few defects. This
method is universal for nanoparticles with different shapes, sizes,
and compositions and for LHP substrates with different metallic cores.
Raman spectroscopic and X-ray diffraction data support our hypothesis
of epitaxial assembly. The novel method offers new insights into the
controllable assembly of complex functional materials and may push
the development of materials science at the mesoscale