4 research outputs found
Growth of Wafer-Scale Standing Layers of WS<sub>2</sub> for Self-Biased High-Speed UV–Visible–NIR Optoelectronic Devices
This
work describes the wafer-scale standing growth of (002)-plane-oriented
layers of WS<sub>2</sub> and their suitability for use in self-biased
broad-band high-speed photodetection. The WS<sub>2</sub> layers are
grown using large-scale sputtering, and the effects of the processing
parameters such as the deposition temperature, deposition time, and
sputtering power are studied. The structural, physical, chemical,
optical, and electrical properties of the WS<sub>2</sub> samples are
also investigated. On the basis of the broad-band light absorption
and high-speed in-plane carrier transport characteristics of the WS<sub>2</sub> layers, a self-biased broad-band high-speed photodetector
is fabricated by forming a type-II heterojunction. This WS<sub>2</sub>/Si heterojunction is sensitive to ultraviolet, visible, and near-infrared
photons and shows an ultrafast photoresponse (1.1 μs) along
with an excellent responsivity (4 mA/W) and a specific detectivity
(∼1.5 × 10<sup>10</sup> Jones). A comprehensive Mott–Schottky
analysis is performed to evaluate the parameters of the device, such
as the frequency-dependent flat-band potential and carrier concentration.
Further, the photodetection parameters of the device, such as its
linear dynamic range, rising time, and falling time, are evaluated
to elucidate its spectral and transient characteristics. The device
exhibits remarkably improved transient and spectral photodetection
performances as compared to those of photodetectors based on atomically
thin WS<sub>2</sub> and two-dimensional materials. These results suggest
that the proposed method is feasible for the manipulation of vertically
standing WS<sub>2</sub> layers that exhibit high in-plane carrier
mobility and allow for high-performance broad-band photodetection
and energy device applications
Silver-Nanowire-Embedded Transparent Metal-Oxide Heterojunction Schottky Photodetector
We
report a self-biased and transparent Cu<sub>4</sub>O<sub>3</sub>/TiO<sub>2</sub> heterojunction for ultraviolet photodetection. The dynamic
photoresponse improved 8.5 × 10<sup>4</sup>% by adding silver
nanowires (AgNWs) Schottky contact and maintaining 39% transparency.
The current density–voltage characteristics revealed a strong
interfacial electric field, responsible for zero-bias operation. In
addition, the dynamic photoresponse measurement endorsed the effective
holes collection by embedded-AgNWs network, leading to fast rise and
fall time of 0.439 and 0.423 ms, respectively. Similarly, a drastic
improvement in responsivity and detectivity of 187.5 mAW<sup>–1</sup> and of 5.13 × 10<sup>9</sup> Jones, is observed, respectively.
The AgNWs employed as contact electrode can ensure high-performance
for transparent and flexible optoelectronic applications
Compliance-Free Multileveled Resistive Switching in a Transparent 2D Perovskite for Neuromorphic Computing
We
demonstrate the pulsed voltage tunable multileveled resistive switching
(RS) across a promising transparent energy material of (C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub>. The X-ray
diffraction and scanning electron microscopy results confirm the growth
of (001) plane-orientated nanostructures of (C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> with an average size
of ∼360 nm. The device depicts optical transmittance higher
than 70% in the visible region and efficient absorbance in the ultraviolet
region. The current–voltage measurement shows the bipolar RS.
In addition, depending on the magnitude of applied electric pulse,
the current across the device can be flipped in four different levels,
which remain stable for long time, indicating multimode RS. Further,
the current across the device increases gradually by applying continuous
pulses, similar to the biological synapses. The observed results are
attributed to the electric field-induced ionic migration across the
(C<sub>4</sub>H<sub>9</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub>. The existing study should open a new avenue to apply this promising
energy material of perovskite for multifunctional advanced devices
Thermally Stable Silver Nanowires-Embedding Metal Oxide for Schottky Junction Solar Cells
Thermally
stable silver nanowires (AgNWs)-embedding metal oxide
was applied for Schottky junction solar cells without an intentional
doping process in Si. A large scale (100 mm<sup>2</sup>) Schottky
solar cell showed a power conversion efficiency of 6.1% under standard
illumination, and 8.3% under diffused illumination conditions which
is the highest efficiency for AgNWs-involved Schottky junction Si
solar cells. Indium–tin–oxide (ITO)-capped AgNWs showed
excellent thermal stability with no deformation at 500 °C. The
top ITO layer grew in a cylindrical shape along the AgNWs, forming
a teardrop shape. The design of ITO/AgNWs/ITO layers is optically
beneficial because the AgNWs generate plasmonic photons, due to the
AgNWs. Electrical investigations were performed by Mott–Schottky
and impedance spectroscopy to reveal the formation of a single space
charge region at the interface between Si and AgNWs-embedding ITO
layer. We propose a route to design the thermally stable AgNWs for
photoelectric device applications with investigation of the optical
and electrical aspects