Amorphous ZnO/PbS Quantum Dots Heterojunction for Efficient Responsivity Broadband Photodetectors

Improvement in Performance and Stability of PbS QD/IGZO Phototransistors Through the Introduction of Ga2O3 Film for Broadband Sensor Applications

The development of broadband photosensors has become crucial in various fields. Indium-gallium-zinc oxide (IGZO, In:Ga:Zn = 1:1:1) phototransistors with PbS quantum dots (QDs) have shown promising features for such sensors, such as reasonable mobility, low leakage current, good photosensitivity, and low-cost fabrication. However, the instability of PbS QD/IGZO phototransistors under an air atmosphere and prolonged storage remain serious concerns. In this article, two concepts to improve the reliability of PbS QD/IGZO phototransistors were implemented. P-type doping in the PbS QD layer through oxidation allows increasing the built-in potential between IGZO and PbS QDs, leading to enhancement in photoinduced electron-hole pair creation. Second, agglomeration and fusion of a PbS QDs layer were controlled via thermal annealing, which facilitated the transport of photocreated carriers. The p-type doping and interconnection of a PbS QD layer can be achieved by deposition and subsequent thermal annealing of gallium oxide (Ga2O3) on PbS QD/IGZO stacks. The resulting Ga2O3/PbS QD/IGZO phototransistors exhibited high-performance switching characteristics under dark conditions. Notably, they showed a remarkable photoresponsivity of 196.69 ± 4.05 A/W and a detectivity of (5.47 ± 1.4) × 1012 Jones even at a long-wavelength illumination of 1550 nm. While the unpassivated PbS/IGZO phototransistor suffered serious degradation in optical performance after 2 weeks of storage, the Ga2O3/PbS QD/IGZO phototransistor demonstrated enhanced stability, maintaining high performance for over 5 weeks. These findings suggest that Ga2O3/PbS QD/IGZO phototransistors offer a feasible approach for the fabrication of large-scale active matrix broadband photosensor arrays, potentially revolutionizing optical sensing in various cutting-edge applications.

Continuous Tunable Energy Band Tailoring Boosts Extending the Sensing of the Waveband Based on (InxGa1-x)2O3 Solar-Blind Photodetectors

Rising wide bandgap semiconductor gallium oxide (Ga2O3) displays huge potential in performing solar-blind photodetection, with constraint in narrow detection wavebands in nature, whereas bandgap modulation through the introduction of exotic atoms into Ga2O3 has an essential effect on the tunable performance of photodetectors and the detection waveband. Here, a novel method for the preparation of (InxGa1-x)2O3 alloy films is proposed, and the continuous tuning of the bandgap in the range of 3.70-4.99 eV is achieved by varying the In-doping content. Alloy-based metal-semiconductor-metal photodetectors were fabricated, achieving a peak responsivity between 254 and 295 nm, superior performance compared to Ga2O3 photodetectors, with a photo-to-dark current ratio as high as 106, and a better optical image-sensing capability. This study offers new insight for high-performance detection of full solar-blind waveband ultraviolet light.

Preparation of a polyaniline/ZnO-NPs composite for the visible-light-driven hydrogen generation

Compositions of ZnO nanoparticles and polyaniline, in the form of emeraldine salt, were manufactured as thin layers by using the spin-coating method. Then, the effect of polyaniline content on their photoelectrochemical characteristics was studied. Results indicate that all the samples are sensitive to light. Besides, with 0.30% of PANI, the composite sample demonstrates the highest photocurrent density; also, its photocurrent increment starts to increase at a voltage of ⁓ 1.23 V (vs. RHE), which is approximately in accordance with the theoretical potential of water electrolysis. Furthermore, since the rate of electron-hole recombination in this composite sample is the lowest, it possesses the highest photoelectrochemical efficiency. Main findings were analyzed with respect to UV-visible absorption and photoluminescence spectra as well as SEM micrographs of the samples and Raman spectral measurements. Besides, electrochemical impedance spectroscopy analysis was applied to both pure ZnO and the sample with the best response. Effects of drying temperature and layer thickness were also investigated.

Flexible and broadband colloidal quantum dots photodiode array for pixel-level X-ray to near-infrared image fusion

Combining information from multispectral images into a fused image is informative and beneficial for human or machine perception. Currently, multiple photodetectors with different response bands are used, which require complicated algorithms and systems to solve the pixel and position mismatch problem. An ideal solution would be pixel-level multispectral image fusion, which involves multispectral image using the same photodetector and circumventing the mismatch problem. Here we presented the potential of pixel-level multispectral image fusion utilizing colloidal quantum dots photodiode array, with a broadband response range from X-ray to near infrared and excellent tolerance for bending and X-ray irradiation. The colloidal quantum dots photodiode array showed a specific detectivity exceeding 1012 Jones in visible and near infrared range and a favorable volume sensitivity of approximately 2 × 105 μC Gy-1 cm-3 for X-ray irradiation. To showcase the advantages of pixel-level multispectral image fusion, we imaged a capsule enfolding an iron wire and soft plastic, successfully revealing internal information through an X-ray to near infrared fused image.

High-Performance Near-Infrared Photodetector Based on PbS Colloidal Quantum Dots/ZnO-Nanowires Hybrid Nanostructures

Quantum dots have found significant applications in photoelectric detectors due to their unique electronic and optical properties, such as tunable bandgap. Recently, colloidal quantum dots (CQDs) have attracted much interest because of the ease of controlling the dot size and low production cost. In this paper, a high-performance ZnO/PbS heterojunction photodetector was fabricated by spin-coating PbS CQDs onto the surface of a hydrothermally grown vertical array of ZnO nanowires (NWs) on an indium tin oxide (ITO) substrate. Under 940 nm near-infrared light illumination, the device demonstrated a responsivity and detectivity of ~3.9 × 10⁴ A/W and ~9.4 × 10¹³ Jones, respectively. The excellent performances and low cost of this nanocomposite-based photodetector show that it has the potential for widespread applications ranging from medical diagnosis to environmental monitoring.

An efficient optical properties of Sn doped ZnO/CdS based solar light driven nanocomposites for enhanced photocatalytic degradation applications

Metal sulfide - semiconductor nanocomposites synthesized with well-defined tin metal, exhibited the wide bandgap, the absorptions are limited to the UV-vis region for reduction of Reactive Blue 160 (RB 160) under solar light irradiation. The prepared samples were characterized using optoelectronic techniques. Conveniently, a wider range of wavelengths and physical properties can be enabled by doping these metal oxide nanoparticles. Whereas the photoreduction of RB 160 is unambiguously associated within charge separation and transmission progression from the excited Sn doped ZnO/CdS. Furthermore, Photocatalytic degradation efficiency for the Sn doped ZnO/CdS composites still reliant on the excitation strength, indicating the several electrons and protons were precise as a result of charge separation and transmission in prepared catalyst. Sn doped ZnO/CdS composites shows 94% Photocatalytic degradation efficiency within 120 min under sunlight irradiation. This photocatalytic nanocomposites may find capable applications in solar cells to power stretchable and also in wearable electronics.

In situ probing the dynamic reconstruction of copper-zinc electrocatalysts for CO2 reduction

Unravelling the dynamic characterization of electrocatalysts during the electrochemical CO₂ reduction reaction (CO₂RR) is a critical factor to improve the production efficiency and selectivity, since most pre-electrocatalysts undergo structural reconstruction and surface rearrangement under working conditions. Herein, a series of pre-electrocatalysts including CuO, ZnO and two different ratios of CuO/ZnO were systematically designed by a sputtering process to clarify the correlation of the dynamic characterization of Cu sites in the presence of Zn/ZnO and the product profile. The evidence provided by in situ X-ray absorption spectroscopy (XAS) indicated that appropriate Zn/ZnO levels could induce a variation in the coordination number of Cu sites via reversing Ostwald ripening. Specifically, the recrystallized Cu site with a lower coordination number exhibited a preferential production of methane (CH₄). More importantly, our findings provide a promising approach for the efficient production of CH₄ by in situ reconstructing Cu-based binary electrocatalysts.

A stretchable ultraviolet-to-NIR broad spectral photodetector using organic-inorganic vertical multiheterojunctions

Stretchable broadband photodetectors (PDs) are attractive for applications in wearable optoelectronics and personal healthcare. However, the development of stretchable broadband PDs is limited by difficulties in obtaining materials, designing device structures, and finding reliable fabrication processes. Here, we report stretchable broadband PDs by forming organic-inorganic vertical multiheterojunctions on a three-dimensionally micro-patterned stretchable substrate (3D-MPSS). The stress-adaptable 3D-MPSS structure allows all layers of the PD coated on it to sustain tensile strains. Generation of photovoltage in the vertical hybrid structure of PbS quantum dots/ZnO nanorods as a photo-responsive material on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) as a transport channel is considred to be the mechanism of the device response to UV-Vis-NIR. The fabricated PDs present responsivity to UV (365 nm), Vis (565 nm and 660 nm), and NIR (880 nm and 970 nm) light, as well as reliable electrical performance under applied stretching up to 30%.

Surface state-induced barrierless carrier injection in quantum dot electroluminescent devices

The past decade has witnessed remarkable progress in the device efficiency of quantum dot light-emitting diodes based on the framework of organic-inorganic hybrid device structure. The striking improvement notwithstanding, the following conundrum remains underexplored: state-of-the-art devices with seemingly unfavorable energy landscape exhibit barrierless hole injection initiated even at sub-band gap voltages. Here, we unravel that the cause of barrierless hole injection stems from the Fermi level alignment derived by the surface states. The reorganized energy landscape provides macroscopic electrostatic potential gain to promote hole injection to quantum dots. The energy level alignment surpasses the Coulombic attraction induced by a charge employed in quantum dots which adjust the local carrier injection barrier of opposite charges by a relatively small margin. Our finding elucidates how quantum dots accommodate barrierless carrier injection and paves the way to a generalized design principle for efficient electroluminescent devices employing nanocrystal emitters.

Hybrid quantum dot light-emitting diodes exhibit barrier-less carrier injection despite a seemingly unfavourable energy landscape. Here, Lee et al. unravel the origin of this barrier-less carrier injection, showing the critical role of surface states of quantum dots.

Selective and Sensitive ZnO Quantum Dots Based Fluorescent Biosensor for Detection of Cysteine

In the present article, a novel and effective ZnO quantum dots-based fluorescent probe has been developed for the detection of cysteine in different solutions. Firstly, melamine-based fluorescent pre-probe was successfully synthesized via condensation reaction and, then ZnO quantum dots (QDs) were homogenously dispersed into this solution. This fluorescent probe was used for the detection of cysteine in different solutions such as bovine serum albumin and tap water. ZnO QDs were characterized using XRD, nano-particle size analyzer, and FE-SEM techniques. The size of the ZnO QDs was calculated as 28.03±9.86 nm, and 31.95±10.02 nm from Scherrer's equation and nano-particle size analyzer, respectively. The developed fluorescent probe was exhibited a highly selective and sensitive response to the detection of cysteine. Also, the proposed fluorescent probe has a larger Stokes shift value (236 nm). The limit of detection and linear range of ZnO QDs-based fluorescent biosensor were found as 0.642 μM and 0.1-600 μM, respectively. ZnO quantum dot-based fluorescent sensor for L-cysteine.

Photodetecting properties of single CuO-ZnO core-shell nanowires with p-n radial heterojunction

CuO-ZnO core-shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO-ZnO core-shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO-ZnO core-shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p-n radial heterojunction diodes based on single CuO-ZnO core-shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO-ZnO core-shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.