9 research outputs found
Improved Electrical Performance and Bias Stability of Solution-Processed Active Bilayer Structure of Indium Zinc Oxide based TFT
We
fabricated active single- and bilayer structure thin film transistors
(TFTs) with aluminum or gallium doped (IZO:Al or IZO:Ga) and undoped
indium zinc oxide (IZO) thin film layers using an aqueous solution
process. The electrical performance and bias stability of these active
single- and bilayer structure TFTs were investigated and compared
to reveal the effects of Al/Gal doping and bilayer structure. The
single-layer structure IZO TFT shows a high mobility of 19 cm<sup>2</sup>/V·s with a poor positive bias stability (PBS) of Δ<i>V</i><sub>T</sub> + 3.4 V. However, Al/Ga doped in IZO TFT reduced
mobility to 8.5–9.9 cm<sup>2</sup>/V·s but improved PBS
to Δ<i>V</i><sub>T</sub> + 1.6–1.7 V due to
the reduction of oxygen vacancy. Thus, it is found the bilayer structure
TFTs with a combination of bottom- and top-layer compositions modify
both the mobility and bias stability of the TFTs to be optimized.
The bilayer structure TFT with an IZO:X bottom layer possess high
mobility and an IZO bottom layer improves the PBS
Sol–Gel Derived Transparent Zirconium-Phenyl Siloxane Hybrid for Robust High Refractive Index LED Encapsulant
We report a zirconium-phenyl siloxane
hybrid material (ZPH) that can be used as a robust LED encapsulant.
The ZPH encapsulant was fabricated via hydrosilylation-curing of sol–gel derived multifunctional (vinyl-
and hydride-functions) siloxane resins containing phenyl-groups and
Zr–O–Si heterometallic phase for achieving a high refractive
index (<i>n</i> ≈ 1.58). In thermal aging, the ZPH
LED encapsulant exhibited superior performances with a high optical
transparency (∼88% at 450 nm) and exhibited high thermal stability
(no yellowing at 180 °C for 1008 h), compared to a commercial
LED encapsulant (OE-6630, Dow Corning Corporation). This suggests
potential for ZPH to be a robust LED encapsulant
Thermally Stable Siloxane Hybrid Matrix with Low Dielectric Loss for Copper-Clad Laminates for High-Frequency Applications
We report vinyl-phenyl siloxane hybrid
material (VPH) that can
be used as a matrix for copper-clad laminates (CCLs) for high-frequency
applications. The CCLs, with a VPH matrix fabricated via radical polymerization
of resin blend consisting of sol–gel-derived linear vinyl oligosiloxane
and bulky siloxane monomer, phenyltrisÂ(trimethylsiloxy)Âsilane, achieve
low dielectric constant (Dk) and dissipation factor (Df). The CCLs
with the VPH matrix exhibit excellent dielectric performance (Dk =
2.75, Df = 0.0015 at 1 GHz) with stability in wide frequency range
(1 MHz to 10 GHz) and at high temperature (up to 275 °C). Also,
the VPH shows good flame resistance without any additives. These results
suggest the potential of the VPH for use in high-speed IC boards
Thermally Stable Siloxane Hybrid Matrix with Low Dielectric Loss for Copper-Clad Laminates for High-Frequency Applications
We report vinyl-phenyl siloxane hybrid
material (VPH) that can
be used as a matrix for copper-clad laminates (CCLs) for high-frequency
applications. The CCLs, with a VPH matrix fabricated via radical polymerization
of resin blend consisting of sol–gel-derived linear vinyl oligosiloxane
and bulky siloxane monomer, phenyltrisÂ(trimethylsiloxy)Âsilane, achieve
low dielectric constant (Dk) and dissipation factor (Df). The CCLs
with the VPH matrix exhibit excellent dielectric performance (Dk =
2.75, Df = 0.0015 at 1 GHz) with stability in wide frequency range
(1 MHz to 10 GHz) and at high temperature (up to 275 °C). Also,
the VPH shows good flame resistance without any additives. These results
suggest the potential of the VPH for use in high-speed IC boards
Ultraviolet Light Stable and Transparent Sol–Gel Methyl Siloxane Hybrid Material for UV Light-Emitting Diode (UV LED) Encapsulant
An
ultraviolet (UV) transparent and stable methyl-siloxane hybrid
material was prepared by a facile sol–gel method. The transparency
and stability of a UV-LED encapsulant is an important issue because
it affects UV light extraction efficiency and long-term reliability.
We introduced a novel concept for UV-LED encapsulation using a thermally
curable oligosiloxane resin. The encapsulant was fabricated by a hydrosilylation
of hydrogen-methyl oligosiloxane resin and vinyl-methyl siloxane resin,
and showed a comparable transmittance to polydimethylsiloxane (PDMS)
in the UVB (∼300 nm) region. Most remarkably, the methyl-siloxane
hybrid materials exhibited long-term UV stability under light soaking
in UVB (∼300 nm) for 1000 h
Quantum Dot/Siloxane Composite Film Exceptionally Stable against Oxidation under Heat and Moisture
We report on the fabrication of a
siloxane-encapsulated quantum
dot (QD) film (QD-silox film), which exhibits stable emission intensity
for over 1 month even at elevated temperature and humidity. QD-silox
films are solidified via free radical addition reaction between oligosiloxane
resin and ligand molecules on QDs. We prepare the QD-oligosiloxane
resin by sol–gel condensation reaction of silane precursors
with QDs blended in the precursor solution, forgoing ligand-exchange
of QDs. The resulting QD-oligosiloxane resin remains optically clear
after 40 days of storage, in contrast to other QD-containing resins
which turn turbid and ultimately form sediments. QDs also disperse
uniformly in the QD-silox film, whose photoluminescence (PL) quantum
yield (QY) remains nearly unaltered under harsh conditions; for example,
85 °C/5% relative humidity (RH), 85 °C/85% RH, strongly
acidic, and strongly basic environments for 40 days. The QD-silox
film appears to remain equally emissive even after being immersed
into boiling water (100 °C). Interestingly, the PL QY of the
QD-silox film noticeably increases when the film is exposed to a moist
environment, which opens a new, facile avenue to curing dimmed QD-containing
films. Given its excellent stability, we envision that the QD-silox
film is best suited in display applications, particularly as a PL-type
down-conversion layer
Quantum Dot/Siloxane Composite Film Exceptionally Stable against Oxidation under Heat and Moisture
We report on the fabrication of a
siloxane-encapsulated quantum
dot (QD) film (QD-silox film), which exhibits stable emission intensity
for over 1 month even at elevated temperature and humidity. QD-silox
films are solidified via free radical addition reaction between oligosiloxane
resin and ligand molecules on QDs. We prepare the QD-oligosiloxane
resin by sol–gel condensation reaction of silane precursors
with QDs blended in the precursor solution, forgoing ligand-exchange
of QDs. The resulting QD-oligosiloxane resin remains optically clear
after 40 days of storage, in contrast to other QD-containing resins
which turn turbid and ultimately form sediments. QDs also disperse
uniformly in the QD-silox film, whose photoluminescence (PL) quantum
yield (QY) remains nearly unaltered under harsh conditions; for example,
85 °C/5% relative humidity (RH), 85 °C/85% RH, strongly
acidic, and strongly basic environments for 40 days. The QD-silox
film appears to remain equally emissive even after being immersed
into boiling water (100 °C). Interestingly, the PL QY of the
QD-silox film noticeably increases when the film is exposed to a moist
environment, which opens a new, facile avenue to curing dimmed QD-containing
films. Given its excellent stability, we envision that the QD-silox
film is best suited in display applications, particularly as a PL-type
down-conversion layer
Complementary p- and n‑Type Polymer Doping for Ambient Stable Graphene Inverter
Graphene offers great promise to complement the inherent limitations of silicon electronics. To date, considerable research efforts have been devoted to complementary p- and n-type doping of graphene as a fundamental requirement for graphene-based electronics. Unfortunately, previous efforts suffer from undesired defect formation, poor controllability of doping level, and subtle environmental sensitivity. Here we present that graphene can be complementary p- and n-doped by simple polymer coating with different dipolar characteristics. Significantly, spontaneous vertical ordering of dipolar pyridine side groups of poly(4-vinylpyridine) at graphene surface can stabilize n-type doping at room-temperature ambient condition. The dipole field also enhances and balances the charge mobility by screening the impurity charge effect from the bottom substrate. We successfully demonstrate ambient stable inverters by integrating p- and n-type graphene transistors, which demonstrated clear voltage inversion with a gain of 0.17 at a 3.3 V input voltage. This straightforward polymer doping offers diverse opportunities for graphene-based electronics, including logic circuits, particularly in mechanically flexible form
Conducting Nanopaper: A Carbon-Free Cathode Platform for Li–O<sub>2</sub> Batteries
For a lithium–oxygen
(Li–O<sub>2</sub>) battery air
electrode, we have developed a new all-in-one platform for designing
a porous, carbon-free conducting nanopaper (CNp), which has dual functions
as catalyst and current-collector, composed of one-dimensional conductive
nanowires bound by a chitin binder. The CNp platform is fabricated
by a liquid diffusion-induced crystallization and vacuum filtration
methods. Employing less than 1 wt % chitin to connect the conductive
skeleton, pores and active sites for reactions have become maximized
in self-standing CNp. The carbon-free CNp enables the Li–O<sub>2</sub> air electrode to be more stably operated compared to carbon
nanofibers and other CNps bound by PVDF and PMMA; side reactions are
largely suppressed on the CNp. The versatile chitin is highlighted
for diverse conducting nanopapers that can be used in various applications