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Here, a photodetector based on Au decorated MoS2/poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonate) PEDOT:PSS nanocomposite films (NCFs) were prepared and their ambipolar (negative and positive) photoresponse under UVC (220–300 nm) and UVA (320–400 nm) UV illumination by increasing the Au decoration on MoS2 in NCFs was reported. This unusual phenomenon relates to the confinement and trapping of charges induced by radiation and plasmons. The hydrothermal technique is employed for generating MoS2 nanosheets. Optical studies reveal the observable bandgap difference resulting from the addition of increasing Au decoration on MoS2 in NCFs. Fourier transform infrared spectroscopy investigations are conducted to comprehend the vibrational characteristics of the produced samples. Carrier localization and trapping generated by photoexcitation and plasmon-induced ambipolar photoresponses provide a versatile control parameter. These results provide opportunities for the application of NCF material in electrical, optical, and optoelectronic devices. The results of this work broaden the pool of potential materials for UVC and UVA photodetectors, perhaps providing new perspectives on the photoresponse of the NCF. [ABSTRACT FROM AUTHOR]

The 2D Bi2Te3 narrow bandgap semiconductor is an outstanding applicant for optoelectronics and thermoelectric devices. The doping of Se into Bi2Te3 makes metal-double chalcogenide more important. In the current investigation, the Se diffusion into the Bi2Te3 film by thermal annealing at different temperatures is probed through a temperature-dependent Raman study along with other characterizations. Upon annealing, the Se/Bi2Te3 films of ∼810 nm thickness resulted in significant changes to their structural, electronic, and optical behavior. The existence of a rhombohedral Bi2Te3 phase was confirmed by structural investigation. The improvement in crystallinity and decrease in lattice strain modified the optical behavior of the films. The morphology analysis showed a slight aggregation at the higher annealed stage. The uniform and homogeneous dispersal and the composition of elements in the film were verified through surface mapping and compositional analysis. The optical investigation revealed a drop in absorbance with increased transmittance. The direct optical bandgap increased from 0.53 ± 0.002 to 0.77 ± 0.002 eV, showing a blue shift. The non-linear refractive index decreased from 3.72 to 1.85 × 10−16 m2/W upon annealing. The temperature-dependent Raman analysis demonstrated a thermally induced significant vibrational change in the material with specific additional peaks at higher annealing. Such findings can be employed as a phase change material at very high temperatures. The obtained findings are very useful for optoelectronic applications. Surface wettability shows a reduction in hydrophilicity, thus inching toward a hydrophobic one with an increase in annealing temperatures. The enhancement in the photocurrent with the increment in the annealing temperature is more suitable for photovoltaic applications. [ABSTRACT FROM AUTHOR]

Engineering transition metal dichalcogenides-based semiconducting two-dimensional (2D) layered materials for photo(electro)chemical (PEC) hydrogen evolution reaction (HER) by water splitting is an enduring challenge. Here, alloy-assisted photoconductivity and photoresponse from CVD-grown MoS2(1-x)Se2x (MSSE) 2D ternary atomic layered alloy-based photodetector device is presented for the realization of PEC HER. The explicit role of ‘S–Se’ and ‘Se2’ atomic alloy sites including chalcogen-induced vacancy defects on the photoconductivity/photoresponse and PEC HER performance of MSSE 2D alloy is investigated. Alloy formation, atomic site-by-site ‘Se’ composition and atomic structure are characterized using Raman/Photoluminescence (PL) spectroscopy, high-angle annular dark field (HAADF)- scanning transmission electron microscopy (STEM) extensively and supported with Auger Electron Spectroscopy (AES) mapping. Further, the local density and concentration of S–Se, Se2 atomic sites and defects were quantitatively estimated using HAADF-STEM image analysis in correlation with AES and it is found between the range of ∼15–20 % in MSSE alloy. A 10-fold high photoresponsivity in the case of MSSE concerning as-grown MS having fast photocurrent growth time and the prolonged decay time originates from the ‘Se’ and this alloy assisted states to enhance the PEC performance of MSSE alloy. The enhanced PEC HER activity of MSSE alloy was identified in terms of overpotential and current density. In addition, increased density of states as a function of ‘Se’ alloying, shifts in a p-band centre and lowers ΔGH* according to density functional theory calculations, which makes MSSE alloy an efficient HER activity. Further, the PEC stability and presence of the ‘S–Se’ and ‘Se2’ alloying and their role towards HER have been correlated by the spectral line shape analysis of PL and Raman spectra from post-PEC HER catalysts. These experimental and theoretical findings establish the role of chalcogen, and transition metal-based 2D alloy, leading to the design of new PECs of engineered 2D atomic layer interfaces.

A new 3D micro-nano integrated M-shaped carbon nanotube (CNT) architecture was designed and fabricated. It is based on vertically aligned carbon nanotube arrays composed of low-density, mainly double-walled CNTs with simple lateral external contacts to the surroundings. Standard optical lithography techniques were used to locally tailor the width of the vertical block structure. The complete sensor system, based on a broadband blackbody absorber region and a high-resistance thermistor region, can be fabricated in a single chemical vapor deposition process step. The thermistor resistance is mainly determined by the high junction resistances of the adjacent aligned CNTs. This configuration also provides low lateral thermal conductivity and a high temperature coefficient of resistance (TCR). These properties are advantageous for new bolometric sensors with high voltage responsivity and broadband absorption from the infrared (IR) to the terahertz spectrum. Preliminary performance evaluations have shown current and voltage responsivities of 2 mA/W and 30 V/W, respectively, in response to IR (980 nm) absorption for a 20 × 20 μm2 device. The device exhibits an exceptionally fast response time of ≈0.15 ms, coupled with a TCR of −0.91 %/K. These attributes underscore its high operating speed and responsivity, respectively. In particular, the device maintains excellent thermal stability and reliable operation at elevated temperatures in excess of 200 °C, extending its potential utility in challenging environmental conditions. This design allows for further device miniaturization using optical lithography techniques. Its unique properties for mass production through large-scale integration techniques make it important for real-time broadband imaging systems.

Owning a narrow bandgap, remarkable optical and electrical properties with notable stability has made cadmium telluride (CdTe) an immensely vital semiconductor to develop cutting-edge optoelectronics. Taking these properties in to account, CdTe thin film is deposited employing the chemical bath deposition (CBD) technique. The X-ray diffraction analysis of the as-deposited thin film unveiled the composite crystalline structure, incorporating cubic, hexagonal, and tetragonal phases. The energy dispersive X-ray analysis and X-ray photoelectron spectroscopy ascertained the chemical composition of CdTe thin film. Distinctive Raman peaks are detected at 141 and 167 cm−1, signifying the presence of Cd-Te bond in the deposited thin film. The comprehensive evaluation of scanning electron micrographs emphasized the firm adhesion of the film to the substrate and displayed a uniform overlay of microstructures resembling rods. The observations from atomic force microscopy unveiled uniform grain structure with topographical features of hills and valleys. The UV-Visible spectroscopic examination elucidated that the as-deposited thin films exhibits a direct optical bandgap value of 1⋅59 eV. Temperature-dependent analysis of d.c. electrical resistivity exhibited a descending pattern, substantiating thin film's semiconducting attributes. The investigation into the photoresponse attributes of the thin film is accomplished by subjecting it to a polychromatic light, green and red monochromatic light source with an intensity of 50 mW/cm² employing three different biasing voltages. The thin film demonstrated maximum photocurrent for red light source than polychromatic and green light with maximum responsivity of 59⋅4 μA/W and detectivity of 17⋅7 × 106 Jones. These findings provide valuable insights on the photoresponse behavior of CBD deposited CdTe thin film in its as-deposited form.

The scientific community is very interested in artificial visual perception systems because of their neuromorphological capabilities, such as image recognition, learning, and memory. This study reports on an organic heterojunction ambipolar transistor with PTCDI‐C8/C8‐BTBT/PTCDI‐C8 sandwich structure. The proposed transistor efficiently transports both holes and electrons, with a current‐on‐switch ratio of ≈106. Furthermore, hole or electron carrier transmission mechanisms are constructed to achieve the controllable adjustment of bi‐directional photoresponse under identical light illumination conditions by adjusting the gate voltage (positive photoresponse for Vg = 30 V and negative photoresponse for Vg = −30 V). The basic synaptic behaviors are simulated under light illumination, and the power consumption of the device is 18.51 fJ per synaptic event, which is comparable to the energy required for biological synapses. Finally, the simulation of human visual adaptation is completed using the bi‐directional photoresponse effects of the organic heterojunction phototransistor array, which provides a novel idea for neuromorphic visual simulation. [ABSTRACT FROM AUTHOR]

Phototransients are investigated for CuSbS2 films with varying the illumination energy. The generation and recombination of photocarriers, which are manifested as changes in the sheet conductivity of the films, take place almost instantaneously for excitation wavelengths of 970 and 633 nm. These rapid responses are, in contrast, absent for the illumination at wavelengths of 375 and 280 nm. In particular, roughly no photoconduction occurs in the case of 280 nm. The sheet conductivity develops thereby random two-level fluctuations following the illumination. Ultraviolet irradiation is thus suggested to generate crystalline defects, giving rise to the quenching of the instantaneous photoresponse caused by their trapping of the photocarriers. The photoresponse in simultaneous illumination at multiple wavelengths is dependent upon the relative intensities of the ultraviolet and visible/infrared components in a nonlinear fashion unless the photo-generated defects are overwhelmed by photocarriers.

Two‐dimensional (2D) intrinsic vacancy semiconductors possess great application prospects in optoelectronics fields, originating from abundant intrinsic vacancy structures and exceptional physical properties. Understanding the structure‐activity relationship between vacancies and physical/photoelectric properties is significant for building advanced photoelectric devices. However, limited by the increasing instability of 2D structure induced by intrinsic vacancies, the precise synthesis of 2D intrinsic vacancy semiconductors faces great challenges. Here, high‐quality 2D intrinsic vacancy semiconductor α‐Ga2Se3 is synthesized via low‐pressure and space‐confined physical vapor deposition. The vacancy structures induce an intermediate energy level and a super‐bandgap photoluminescence (PL) peak, which are verified by temperature‐dependent PL spectra. Furthermore, the vacancy energy level favorably endows 2D α‐Ga2Se3‐based photodetector with a UV‐vis‐NIR super‐bandgap photoresponse, excellent ultraviolet detection ability (photoresponsivity (41.86 A W−1), epitaxial quantum efficiency (1.42 × 104%), and detectivity (6.69 × 1011 Jones) @365 nm), fast photoresponse (20 ms), and superior photocurrent‐light power‐fitting factors. In addition, 2D α‐Ga2Se3‐based phototransistor displays p‐type transport behavior with a responsivity of 105 A W−1@365 nm at a gate voltage of −40 V. This work suggests a bright future of 2D intrinsic vacancy semiconductors in tailoring physical properties and enabling sophisticated device functionality.