3 research outputs found
Single-Photon-Camera-Based Time and Spatially Resolved Electroluminescence Spectroscopy for Micro-LED Analysis
To
investigate the operational mechanisms of micrometer-sized light-emitting
diodes (micro-LEDs), we here demonstrate a transient methodology of
time and spatially resolved electroluminescence spectroscopy (TSR-EL)
to measure the spatial distribution of light emission from LED devices.
By combining a single-photon camera (SPC) with the time-gated sampling
method, we derived the time and spatially resolved electroluminescence
intensity with increasing time. Benefiting from the high sensitivity
of the SPC, this methodology can detect ultralow electroluminescence
(EL) at the delay stage from the device operated around the turn-on
voltage. Furthermore, we investigated the spatial light distribution
of a typical quantum dots light-emitting diode (QLED) under different
applied voltages and varied temperatures. It was found that the EL
emission of the QLED device became more uniform with increasing temperature
and applied voltage. Moreover, the methodology of TSR-EL is versatile
to investigate other LEDs such as organic light-emitting diodes (OLEDs),
micro-LEDs, etc
Three-Dimensional Dual-Site Catalysts for Industrial Ammonia Synthesis at Dramatically Decreased Temperatures and Pressures
Industrial
ammonia (NH3) production via the Haber–Bosch
(H–B) process is a great achievement of the 20th century, but
its energy-intensive character renders NH3 production costly.
Despite considerable efforts, progress in developing an efficient
H–B catalyst that operates under near-ambient conditions has
been slow. In this study, we leverage the confinement concept to facilitate
low-temperature and low-pressure NH3 synthesis by constructing
three-dimensional (3D) dual-site environments. Through first-principles
calculations and microkinetic modeling, we demonstrate that the 3D
confined dual site on diporphyrins can surpass the limitations imposed
by energy-scaling relations, resulting in a significantly increased
turnover frequency (TOF) for NH3 production. Notably, the
calculated TOF is 2–3 orders of magnitude higher than that
of the commercial ruthenium catalyst at the same working conditions,
thus enabling a much-milder H–B process, e.g., at a dramatically
decreased working pressure of 10 bar at 590 K. We believe that the
strategy will pave the way for the development of economically viable
alternatives to current industrial processes
Influence of Shell Thickness on the Performance of NiO-Based All-Inorganic Quantum Dot Light-Emitting Diodes
The
effect of shell thickness on the performance of all-inorganic
quantum dot light-emitting diodes (QLEDs) is explored by employing
a series of green quantum dots (QDs) (Zn<sub><i>x</i></sub>Cd<sub>1–<i>x</i></sub>Se/ZnS core/shell QDs with
different ZnS shell thicknesses) as the emitters. ZnO nanoparticles
and sol–gel NiO are employed as the electron and hole transport
materials, respectively. Time-resolved and steady-state photoluminescence
results indicate that positive charging processes might occur for
the QDs deposited on NiO, which results in emission quenching of QDs
and poor device performance. The thick shell outside the core in QDs
not only largely suppresses the QD emission quenching but also effectively
preserves the excitons in QDs from dissociation of electron–hole
pairs when they are subjected to an electric field. The peak efficiency
of 4.2 cd/A and maximum luminance of 4205 cd/m<sup>2</sup> are achieved
for the device based on QDs with the thickest shells (∼4.2
nm). We anticipate that these results will spur progress toward the
design and realization of efficient all-inorganic QLEDs as a platform
for the QD-based full-colored displays