15 research outputs found
Role of Intrinsic Ion Accumulation in the Photocurrent and Photocapacitive Responses of MAPbBr<sub>3</sub> Photodetectors
We studied steady state and transient
photocurrents in thin film
and single-crystal devices of MAPbBr<sub>3</sub>, a prototype organicâinorganic
hybrid perovskite. We found that the devicesâ capacitance is
abnormally large, which originates from accumulation of large densities
of Pb<sup>2+</sup> and Br<sup>â</sup> in the active perovskite
layer. Under applied bias, these ions are driven toward the opposite
electrodes leading to space-charge fields close to the metal/perovskite
interfaces. The ion accumulation, in turn, causes photocurrent reversal
polarity that depends on the history of the applied bias and excitation
photon energy with respect to the optical gap. Furthermore, the large
capacitive response dominates the transient photocurrent and, therefore,
obscures the weaker contribution from the photocarriersâ drift.
We show that these properties depend on the ambient conditions in
which the measurements are performed. Understanding these phenomena
may lead to better control over the stability of perovskite photodetectors
for visible light
Manipulation of Emission Colors Based on Intrinsic and Extrinsic Magneto-Electroluminescence from Exciplex Organic Light-Emitting Diodes
Exciplex organic light-emitting diodes
(XOLEDs) utilize nonemissive
triplet excitons via a reverse intersystem crossing process of thermally
activated delayed fluorescence. The small energy difference between
the lowest singlet and triplet levels of exciplex also allows a magnetic
field to manipulate their populations, thereby achieving ultralarge
âintrinsicâ magneto-electroluminescence (MEL) in XOLEDs.
Here we incorporate it into a hybrid type of spintronic device (âhybrid
spin-XOLEDâ), where the XOLED is connected to a magnetic tunnel
junction with large magnetoresistance, to introduce an âextrinsicâ
MEL response that interferes with the âintrinsicâ MEL.
The ratio between two MEL contributions, the MEL value, and the field
response were altered by changing the exciplex layer thickness or
actively manipulated by adding another current source that drives
the XOLED. Most importantly, by involving two XOLEDs (green and red)
in the same circuit, the hybrid spin-XOLED shows a color change when
sweeping the magnetic field, which provides an alternative way for
future OLED display technologies
Electroabsorption Spectroscopy Studies of (C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>4</sub> OrganicâInorganic Hybrid Perovskite Multiple Quantum Wells
Two-dimensional (2D)
organicâinorganic hybrid perovskite
multiple quantum wells that consist of multilayers of alternate organic
and inorganic layers exhibit large exciton binding energies of order
of 0.3 eV due to the dielectric confinement between the inorganic
and organic layers. We have investigated the exciton characteristics
of 2D butylammonium lead iodide, (C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>4</sub> using photoluminescence and UVâvis
absorption in the temperature range of 10 K to 300 K, and electroabsorption
spectroscopy. The evolution of an additional absorption/emission at
low temperature indicates that this compound undergoes a phase transition
at â250 K. We found that the electroabsorption spectrum of
each structural phase contains contributions from both quantum confined
exciton Stark effect and FranzâKeldysh oscillation of the continuum
band, from which we could determine more accurately the 1s exciton,
continuum band edge, and the exciton binding energy
Machine-Learning-Driven Discovery of Mn<sup>4+</sup>-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays
The discovery of high-efficiency Mn4+-activated
fluoride
red phosphors with short excited-state lifetimes (ESLs) is urgent
and crucial for high-quality, wide-color-gamut display applications.
However, it is still a great challenge to design target phosphors
with both short ESL and high luminescence efficiency. Herein, we propose
an efficient machine learning approach based on a small dataset to
establish the ESL prediction model, thereby facilitating the discovery
of new Mn4+-activated fluorides with short ESLs. Such a
model can not only accurately predict the ESLs of Mn4+ in
fluorides but also quantify the impact of structure features on ESLs,
therefore elucidating the âstructure-lifetimeâ correlations.
Guided by the correlations, two new Mn4+-doped tetramethylammonium
(TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (Ï â€ 3.7
ms) and high quantum efficiencies (internal QEs > 92%, external
QEs
> 55%) have been discovered successfully. A prototype displayer
with
excellent performance (âŒ124% National Television Standards
Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight
module, demonstrating its practical prospects in high-quality displays.
This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference
for accelerating the discovery of new promising phosphors
Machine-Learning-Driven Discovery of Mn<sup>4+</sup>-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays
The discovery of high-efficiency Mn4+-activated
fluoride
red phosphors with short excited-state lifetimes (ESLs) is urgent
and crucial for high-quality, wide-color-gamut display applications.
However, it is still a great challenge to design target phosphors
with both short ESL and high luminescence efficiency. Herein, we propose
an efficient machine learning approach based on a small dataset to
establish the ESL prediction model, thereby facilitating the discovery
of new Mn4+-activated fluorides with short ESLs. Such a
model can not only accurately predict the ESLs of Mn4+ in
fluorides but also quantify the impact of structure features on ESLs,
therefore elucidating the âstructure-lifetimeâ correlations.
Guided by the correlations, two new Mn4+-doped tetramethylammonium
(TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (Ï â€ 3.7
ms) and high quantum efficiencies (internal QEs > 92%, external
QEs
> 55%) have been discovered successfully. A prototype displayer
with
excellent performance (âŒ124% National Television Standards
Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight
module, demonstrating its practical prospects in high-quality displays.
This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference
for accelerating the discovery of new promising phosphors
Magnetic-Field-Driven Reconfigurable Microsphere Arrays for Laser Display Pixels
Reconfigurable
microlaser arrays are essential to the construction
of display panels where the individual pixel should be highly tunable
in resonance mode, optical polarization, and lasing wavelength upon
external control signals. Here we demonstrate a facile yet reliable
approach to fabrication of organic microlaser pixels, in which the
assembly of microsphere arrays on each pixel is controlled according
to the near-field magnetostatic confinement. The geometrical configuration
of diamagnetic microspheres could be readily modulated with the near-field
potential traps by using the external field to alternate the saturation
magnetization of the underneath micromagnet. The motion of microspheres
can be modulated among several states upon applied field, and the
reconfigurable microsphere array is thus achieved with high spatial
precision and rapid temporal response. Moreover, both isolated and
coupled spheres serve as low-threshold microlasers with tunable optical
resonance modes, whereas the switching between the vertical and horizontal
alignments of coupled spheres manipulates the polarization of lasing
outputs. By repeating the magnetostatic confinement on the same substrate,
the full-color laser display pixels with magnetically tunable color
expression capability are successfully achieved
Machine-Learning-Driven Discovery of Mn<sup>4+</sup>-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays
The discovery of high-efficiency Mn4+-activated
fluoride
red phosphors with short excited-state lifetimes (ESLs) is urgent
and crucial for high-quality, wide-color-gamut display applications.
However, it is still a great challenge to design target phosphors
with both short ESL and high luminescence efficiency. Herein, we propose
an efficient machine learning approach based on a small dataset to
establish the ESL prediction model, thereby facilitating the discovery
of new Mn4+-activated fluorides with short ESLs. Such a
model can not only accurately predict the ESLs of Mn4+ in
fluorides but also quantify the impact of structure features on ESLs,
therefore elucidating the âstructure-lifetimeâ correlations.
Guided by the correlations, two new Mn4+-doped tetramethylammonium
(TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (Ï â€ 3.7
ms) and high quantum efficiencies (internal QEs > 92%, external
QEs
> 55%) have been discovered successfully. A prototype displayer
with
excellent performance (âŒ124% National Television Standards
Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight
module, demonstrating its practical prospects in high-quality displays.
This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference
for accelerating the discovery of new promising phosphors
Machine-Learning-Driven Discovery of Mn<sup>4+</sup>-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays
The discovery of high-efficiency Mn4+-activated
fluoride
red phosphors with short excited-state lifetimes (ESLs) is urgent
and crucial for high-quality, wide-color-gamut display applications.
However, it is still a great challenge to design target phosphors
with both short ESL and high luminescence efficiency. Herein, we propose
an efficient machine learning approach based on a small dataset to
establish the ESL prediction model, thereby facilitating the discovery
of new Mn4+-activated fluorides with short ESLs. Such a
model can not only accurately predict the ESLs of Mn4+ in
fluorides but also quantify the impact of structure features on ESLs,
therefore elucidating the âstructure-lifetimeâ correlations.
Guided by the correlations, two new Mn4+-doped tetramethylammonium
(TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (Ï â€ 3.7
ms) and high quantum efficiencies (internal QEs > 92%, external
QEs
> 55%) have been discovered successfully. A prototype displayer
with
excellent performance (âŒ124% National Television Standards
Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight
module, demonstrating its practical prospects in high-quality displays.
This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference
for accelerating the discovery of new promising phosphors
Magnetic-Field-Driven Reconfigurable Microsphere Arrays for Laser Display Pixels
Reconfigurable
microlaser arrays are essential to the construction
of display panels where the individual pixel should be highly tunable
in resonance mode, optical polarization, and lasing wavelength upon
external control signals. Here we demonstrate a facile yet reliable
approach to fabrication of organic microlaser pixels, in which the
assembly of microsphere arrays on each pixel is controlled according
to the near-field magnetostatic confinement. The geometrical configuration
of diamagnetic microspheres could be readily modulated with the near-field
potential traps by using the external field to alternate the saturation
magnetization of the underneath micromagnet. The motion of microspheres
can be modulated among several states upon applied field, and the
reconfigurable microsphere array is thus achieved with high spatial
precision and rapid temporal response. Moreover, both isolated and
coupled spheres serve as low-threshold microlasers with tunable optical
resonance modes, whereas the switching between the vertical and horizontal
alignments of coupled spheres manipulates the polarization of lasing
outputs. By repeating the magnetostatic confinement on the same substrate,
the full-color laser display pixels with magnetically tunable color
expression capability are successfully achieved