Type Photodetector Research Articles

Ion Migration as a New Paradigm to Boost Self‐Driven Perovskite Narrowband Photodetectors

AbstractHalide perovskite narrowband photodetectors based on a charge collection narrowing mechanism have emerged as a new class of optoelectronic devices for monochromatic imaging. However, improving the figures‐of‐merit of such narrowband photodetectors remains challenging due to the inability to manipulate the major material players in the elusive photoresponse process. Here, a novel approach of manipulating ion migration to enhance the narrowband photoresponse of self‐driven p‐i‐n type photodetectors is taken by intentionally adding mobile ions into the formamidine and methylamine mixed cation perovskite layer. The excess mobile ions reduce the activation energy of ion migration, and this facilitated migration orchestrates the ions in the perovskite layer to re‐engineer the energy band, and thus modulates the charge separation and collection energetics and kinetics, leading to an unprecedented boost of the narrowband photoresponse. The photodetector based on this approach achieved a peak responsivity of as high as 112.41 mA W−1 at 820 nm at zero bias with a full‐width at half maximum of only 22 nm and an over 3‐fold improvement in the spectral rejection ratio, making it highly promising for the next‐generation color imaging devices.

Flexible metal/semiconductor/metal type photodetectors based on manganese doped ZnO nanorods

High-performance flexible photodetectors are one of the most interesting research areas due to their great possibilities for a variety of applications such as portable and wearable optoelectronics. This study verifies the performance of flexible metal/semiconductor/metal-type photodetector based on pristine and manganese doped ZnO nanorods (ZnO-NRs) prepared in two different concentrations of zinc precursors and manganese dopant at low temperatures. The photodetectors having ZnO-NRs with high aspect ratios were investigated by various material characterization techniques such as electron paramagnetic resonance and photoluminescence spectroscopy to confirm the relationship between defect concentrations and photodetector performance parameters. It has been calculated that the detectivity (D*) and responsivity (R) of the ZnO nanorod-based photodetectors increased 20 and 18 folds, respectively by increasing the concentration of zinc precursor. Besides the D* and R values of the photodetectors, prepared by the 16.5 mM zinc precursor, increased 18 and 4.5-fold, respectively, after manganese doping. We confirmed that even a very low concentration of zinc precursor could produce a photodetector with high performance in photo-response characteristics, flexibility, and stability against 10,000 cycles of convex/concave bending.

Bismuth nanoplatelets: universal synthetic strategy and emerging application for PEC-type photodetectors

Bi nanoplatelets (NPLs) with a narrow size distribution and high yield have been successfully fabricated by a novel two-step sonication-assisted solvothermal method. Applied as photo-electrochemical (PEC)-type photodetectors (PDs), it is shown that the Bi NPLs exhibit a pronounced photo-response ranging from the ultraviolet to the visible regions. The photo-response performance of Bi NPLs-based PDs was adjusted by external conditions and interpreted by density functional theory calculations in terms of the formation of the respective Bi-based compounds. The PEC results demonstrate that the optimal photocurrent density (Pph) and photoresponsivity (Rph) can reach 12.27 μA/cm2 and 3016 μA/W in alkaline electrolytes, respectively. Besides, the Bi NPLs-based PDs exhibit superb long-term cycling stability (∼97.86% remained after 1000 cycles). We conclude that Bi NPLs demonstrate great promise as an emerging building block for the design of high-performance PEC-type PDs as well as other novel optoelectronic devices, holding the potential for breakthrough developments in these fields.

Catalyst-Free β-Ga2O3@a-Ga2O3 Core−Shell nanorod arrays grown on Si substrate for High-performance self-powered solar-blind photoelectrochemical photodetection

Self-powered photodetectors are recognized as one of the developing trends of next-generation optoelectronic devices. Particularly, a novel photoelectrochemical (PEC) type photodetectors have attracted a great deal of attention due to the advantages of low cost and self-powered capability. Herein, we construct, for the first time, solar-blind PEC-type photodetectors based on amorphous Ga2O3-covered β-Ga2O3 (denoted as β-Ga2O3@a-Ga2O3) core−shell nanorod arrays (NRAs) synthesized on silicon substrates using a simple one-step catalyst-free CVD method. The as-fabricated self-powered solar-blind photodetector has comprehensive photodetection performance in terms of a maximum responsivity of 48.4 mA/W, a high detectivity of 8.5 × 1011 Jones as well as fast response and recovery times (tres/trec = 125/160 ms) under 254 nm illumination with a light intensity of 0.1 mW/cm2, outperforming most of the reported Ga2O3 based PEC-type devices to date. Furthermore, the device shows good multicycle stability and repeatability. Such outstanding solar-blind photodetection performance is largely attributed to the superior crystalline quality of catalyst-free grown β-Ga2O3@a-Ga2O3 core−shell NRAs and the additional built-in electric field of a-Ga2O3 and β-Ga2O3 interface. This work provides a simple and feasible route for constructing Ga2O3-based PEC-type solar-blind photodetectors with high performance, stability and low cost.

Ultrathin 2D Violet Phosphorus Nanosheets: Facile Liquid‐Phase Exfoliation, Characterization, and Photoelectrochemical Application

AbstractViolet phosphorus (VP) is a stable layered van der Waals phosphorus allotrope with unique electronic and optoelectronic properties. In this study, 2D VP nanosheets (NSs) are prepared by liquid phase exfoliation (LPE) method under ambient conditions. The prepared VP NSs are characterized and utilized for photoelectrochemical (PEC)‐type photodetector (PD). The systematic PEC measurements reveal that the as‐prepared VP‐based PD shows tunable photo‐response activities from ultraviolet to visible region. A current density of 0.52 µA cm−2, a photo‐responsivity of 31.70 µA W−1, and a detectivity of 7.92 × 1010 Jones can be obtained in 1.0 m KOH under 350 nm irradiation at 0 V, revealing the good self‐powered capability of VP‐based PD. Furthermore, the cycle and time stability tests exhibit the good chemical and environmental stability of the as‐prepared PD via processing 10 000 s on/off switching and placing after one month. It is expected that this work can offer an understanding of a PEC‐type VP NSs‐based PD, and highlight the further promising applications of 2D VP NSs for other optoelectronic devices.

Highly Sensitive and Stable Visible-Light Self-Power Photodetectors Based on Solution-Processed Bi4O5I2

Bismuth oxyiodides have been gradually regarded as a kind of promising optoelectronic material, owing to their various merits, like relatively narrow and tunable band gap, high anisotropic crystal structure, and less toxicity. However, the investigation of bismuth oxyiodide-based photodetectors is still in the early stage, which might be attributed to the immature film deposition techniques in controlling their phase composition and surface morphology. In this work, high-quality Bi4O5I2 thin films were synthesized for the first time by a facile solution-based deposition technique, mist chemical vapor deposition. The synthesized Bi4O5I2 thin films were composed of vertically aligned nanoplatelets. With the increasing synthesis temperatures, the size of the nanoplates and film thickness increased. The iodide content was influenced by the synthesis temperatures such that the I:Bi molar ratio for the Bi4O5I2 thin films at intermediate temperature was close to 50%. The Bi4O5I2 photoelectrochemical (PEC)-type photodetectors were fabricated and exhibited excellent photodetection performance with the highest responsivity of 19.4 mA/W and detectivity of 3.54 × 1010 Jones. In addition, Bi4O5I2 PEC-type photodetectors presented good long-term stability in that the photocurrent density only decreased by around 25% after 6 h, which was superior to most 2D material-based PEC-type photodetectors. These results demonstrated that the Bi4O5I2 thin film has great potential in high-performance optoelectronic devices.

A wire-shaped photoanode of the solar-blind photoelectrochemical-type photodetector based on an α-Ga2O3 nanorods/electrolyte solid/liquid heterojunction

Multifunctional and smart solar-blind photodetectors are of great significance for many applications, particularly for communications, optoelectronic circuits, and environmental risk monitoring. In this study, a wire-shaped photoanode of the solar-blind photoelectrochemical (PEC)-type photodetector based on an α-Ga2O3 nanorods/electrolyte solid/liquid heterojunction is realized. In photovoltaic devices, a junction generally comprises two different solid materials to facilitate the separation of photogenerated electron–hole pairs. Similarly, a solid/liquid junction is formed between the semiconductor and the electrolyte in a PEC photodetector. The apparent rectification characteristics of the dark current indicate that the energy bands bend at the α-Ga2O3 nanorods/electrolyte interface. The local electric field in the semiconductor effectively promotes the separation of carriers. The photodetectors exhibit a high light/dark current ratio (Ilight/Idark) of 68.7; fast rise and decay response times of 0.1 and 0.06 s, respectively; and a high responsivity of 11.2 mA/W (@230 nm) at zero bias. The wire-shaped photoanode is beneficial for realizing potential omnidirectional solar-blind detection.

Rapid growth of a 24 mm2 scale hexagonal boron nitride crystal in Ni–Cr solution

A 24 mm2 exfoliated hBN film is achieved within a total growth time of 49.17 hours. A signal-to-noise ratio of 2 orders of magnitude is reported for a metal–semiconductor–metal type photodetector based on hBN.

CuBi2O4nanocrystals integrated with polyaniline nanobelt arrays for weak light photomultiplication type photodetector

Novel CuBi2O4nanocrystals incorporated in the polyaniline matrix utilized for the fabrication of a flexible and bio-compatible device for the detection of low-intensity photons by using a photomultiplication type photodetector.

Bi2 Te3 /Bi2 Se3 /Bi2 S3 Cascade Heterostructure for Fast-Response and High-Photoresponsivity Photodetector and High-Efficiency Water Splitting with a Small Bias Voltage.

Large-scale multi-heterostructure and optimal band alignment are significantly challenging but vital for photoelectrochemical (PEC)-type photodetector and water splitting. Herein, the centimeter-scale bismuth chalcogenides-based cascade heterostructure is successfully synthesized by a sequential vapor phase deposition method. The multi-staggered band alignment of Bi2 Te3 /Bi2 Se3 /Bi2 S3 is optimized and verified by X-ray photoelectron spectroscopy. The PEC photodetectors based on these cascade heterostructures demonstrate the highest photoresponsivity (103mAW-1 at -0.1V and 3.5mAW-1 at 0V under 475nm light excitation) among the previous reports based on two-dimensional materials and related heterostructures. Furthermore, the photodetectors display a fast response (≈8ms), a high detectivity (8.96×109 Jones), a high external quantum efficiency (26.17%), and a high incident photon-to-current efficiency (27.04%) at 475nm. Due to the rapid charge transport and efficient light absorption, the Bi2 Te3 /Bi2 Se3 /Bi2 S3 cascade heterostructure demonstrates a highly efficient hydrogen production rate (≈0.416mmolcm-2 h-1 and ≈14.320µmolcm-2 h-1 with or without sacrificial agent, respectively), which is far superior to those of pure bismuth chalcogenides and its type-II heterostructures. The large-scale cascade heterostructure offers an innovative method to improve the performance of optoelectronic devices in the future.

Preparation of high-performance Sb2S3 based visible-light photodetector with excellent reversibility

In this study, Sb2S3 films were prepared by dip coating method at 250, 300, 350, 400 and 450 °C temperatures. No heat treatment was applied other than the coating temperatures. XRD, SEM, EDX and photoluminescence measurements of the prepared films were carried out. In addition, metal-semiconductor-metal (MSM) type photodetectors were prepared using Sb2S3 films. According to XRD and SEM results, films coated at 250 °C are still in amorphous structure. On the other hand, the films begin to crystallize at 300 °C. The EDX results show that the S/Sb ratio of Sb2S3 films varies between 1.35 and 1.55 depending on the coating temperature. Photoluminescence results show a strong emission peak with an energy value of 1.98 eV for all samples. Photocurrents of the prepared photodetectors vary between 0.44 and 48.15 nA depending on the coating temperature. A photosensitivity of 56.81 was observed with the photodetector prepared at 400 °C. In addition, Sb2S3 photodetectors prepared at 400 °C exhibit rise and decay times of ∼0.4 and ∼0.4 s, respectively with an excellent reversibility.

Enhanced photoresponse of InxMo1-xS2 (X = 0.05 and 0.1) nanosheets for PEC type photodetector

Transition metal chalcogenides (TMDCs) have great potential in the field of solid state photodetectors and photoelectrochemical (PEC) type photodetector owing to high carrier mobility and suitable energy band gap. Two dimensional MoS2, most intensively investigated member of TMDCs, has shown excellent photoresponsivity in the visible range owing to excitonic transition and suitable electronic structure. Herein, we demonstrate the PEC photodetector based on InxMo1-xS2 nanosheets. High yield liquid phase exfoliation techniques have been employed for the synthesis of InxMo1-xS2 nanosheets. InxMo1-xS2 nanosheets have hexagonal lattice structure with highly crystalline behavior and X-ray diffraction confirms the doping of indium in 2H–MoS2. PEC type detectors show 582 μA/W and 107 μA/W photoresponsivity for In0.05Mo0.95S2 and In0.1Mo0.9S2 nanosheets by optimized concentration of indium. Present investigation advocates the significant development in the field of opto-electronics and photoelectrochemical cells for generation clean energy.

Performance of passivation layer for InP/InGaAs based short-wave infrared photodetector

The surface passivation effects of SiNx films deposited by plasma-enhanced chemical vapour deposition (PECVD) technique are investigated for InP/In0.53Ga0.47As mesa type photodetectors. It is found that the deposited SiNx film effectively reduces the densities of interface states (Dit) and slow trapped charge (Nt) near SiNx/In0.53Ga0.47As interface using NH4OH based pre-passivation treatment. The fixed charge density of 1.98 × 1011 C/cm2, the minimum value of Dit ∼3.2 × 1011 cm−2 eV−1 and Nt of 4.2 × 1011 C/cm2 are determined from the experimental capacitance-voltage curve of Ti–Au/SiNx/In0.53Ga0.47As based metal-insulator-semiconductor structure. Lower values of passivation properties indicate smaller surface recombination centre and lower surface leakage current. Thus, minimum noise related to dark current could be achieved for InP/In0.53Ga0.47As based mesa structured detector array with smaller pitch at room temperature.

Type-I SnSe2/ZnS heterostructure improving photoelectrochemical photodetection and water splitting

Two-dimensional van der Waals heterostructures have been widely designed and applied to numerous optoelectronic devices such as photoelectrochemical (PEC)-type photodetectors, water splitting, and solar cells. The understanding of the influence of band alignment in type-I heterostructures on the photoelectric response remains incomplete yet essential for designing new optoelectronic devices. Herein, two-step physical vapor deposition is used to construct a type-I SnSe2/ZnS heterostructure, which is confirmed by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The type-I heterostructure-based PEC-type photodetector exhibits excellent photoresponse, high stability, and high sensitivity in the ultraviolet-visible range. Furthermore, the photoresponsivity of SnSe2/ZnS is up to 172.60 µA W−1, which is 7.4- and 2.0-fold larger than that of pure ZnS and SnSe2, respectively. Moreover, the SnSe2/ZnS heterostructure possesses high photoelectrocatalytic activity in water splitting, and the total hydrogen production within 2 h is up to 81.25 µmol cm−2. The high PEC-type photodetector and water splitting performances in SnSe2/ZnS are due to the synergistic effect of high light utilization and efficient charge transport. Our work provides a new method for improving photoelectric response by forming type-I heterostructures and for designing high-performance optoelectronic devices for photodetectors and water splitting.

Ti3C2T x MXene anchoring semi-metallic selenium atoms: self-powered photoelectrochemical-type photodetector, hydrogen evolution, and gas-sensing applications

MXenes have demonstrated substantial promise as photocatalysts and electrocatalysts for a variety of applications such as self-powered photoelectrochemical (PEC)-type photodetector, hydrogen evolution reaction (HER), and vapor sensing applications. However, their mechanism is still poorly figured out. Currently, Ti3C2T x MXene suffers from low photoresponsivity, high overpotential, and low sensitivity in such important applications. In order to develop catalytic activity and performances of those devices, modifications must be made to the structure of MXenes to enhance the separation of photogenerated charges, rate of the H+/e− couplings, and surface-active sites. These manipulations of MXenes heavily depend on understanding the mechanism of devices, appropriate modification elements, and the method of modification. This study for the first time reveals a facile solid-state annealing strategy for doping semi-metallic selenium (Se) atoms on Ti3C2T x MXene for self-powered PEC-type photodetector, HER, and vapor sensor applications. The suitable characteristics of Ti3C2T x make it an appropriate substrate to accommodate Se atoms. The well-designed Se-doped Ti3C2 heterojunction including some TiO2 cuboids could exhibit unprecedented photoresponsivity (up to 90 mA W−1) and detectivity (up to 2.0 × 108 cm Hz1/2 W−1) for 420 nm light, HER (−0.7 V at 10 mA cm−2), and gas sensitivity (Z′ = 347 Ω and Z′′ = 150 Ω, for ethanol) in comparison with the pristine Ti3C2T x nanosheets. The acquired promising results can be promoted with some other elements and also be examined in other electrolytes. Then, bring inspiration to the applications involving charge transfer, H+/e− couplings, and surface-active sites.

Broadband self-powered photoelectrochemical photodetector based on Te/Se heterostructure nanocomposites

Van der Waals (vdW) heterojunctions formed from different nanomaterials not only have the characteristics of each material but also exhibit novel physical properties due to the combination of them. In this work, we report on the facile synthesis of Te/Se heterostructure nanocomposites, and their application as a photosensitive material for photoelectrochemical (PEC)-type photodetectors. The Te/Se-based PEC-type photodetectors are found to achieve excellent photodetection performance and have a broad optical response spectrum that covers the ultraviolet (365 nm) to near-infrared (980 nm) regions. With 1.0 M KOH as the electrolyte, the Te/Se-based PEC-type photodetectors exhibit a photoresponsivity of 4.04 μA W−1, a specific detectivity of 1.6 × 107 Jones, and a fast response time of less than 0.2 s under 365 nm illumination at 0 V, indicating excellent self-powered capability. Additionally, under an applied bias potential of 0.6 V, the photodetectors exhibit a high photoresponsivity of up to 83.19 μA W−1 and a specific detectivity of 3.3 × 108 Jones. Moreover, the Te/Se-based PEC-type photodetectors show good cycle stability after loop running for 1500 s.

Tin Oxide (SnO2) Nanoparticles: Facile Fabrication, Characterization, and Application in UV Photodetectors.

Tin oxide (SnO2) nanomaterials are of great interest in many fields such as catalytic, electrochemical, and biomedical applications, due to their low cost, suitable stability characteristics, high photosensitivity, etc. In this contribution, SnO2 NPs were facilely fabricated by calcination of tin (II) oxalate in air, followed by a liquid-phase exfoliation (LPE) method. Size-selected SnO2 NPs were easily obtained using a liquid cascade centrifugation (LCC) technique. The as-obtained SnO2 NPs displayed strong absorption in the UV region (~300 nm) and exhibited narrower absorption characteristics with a decrease in NP size. The as-fabricated SnO2 NPs were, for the first time, directly deposited onto a poly(ethylene terephthalate) (PET) film with a regular Ag lattice to fabricate a flexible working electrode for a photoelectrochemical (PEC)-type photodetector. The results demonstrated that the SnO2-NP-based electrode showed the strongest photoresponse signal in an alkaline electrolyte compared with those in neutral and acidic electrolytes. The maximum photocurrent density reached 14.0 μA cm−2, significantly outperforming black phosphorus nanosheets and black phosphorus analogue nanomaterials such as tin (II) sulfide nanosheets and tellurene. The as-fabricated SnO2 NPs with relatively larger size had better self-powered photoresponse performance. In addition, the as-fabricated SnO2-NP-based PEC photodetector exhibited strong cycling stability for on/off switching behavior under ambient conditions. It is anticipated that SnO2 nanostructures, as building blocks, can offer diverse availabilities for high-performance self-powered optoelectronic devices to realize a carbon-neutral or carbon-free environment.

Electrophoretic deposition of MoS2 nanosheets for photoelectrochemical type photodetector

Herein, we demonstrate the electrophoretic deposition of MoS2 nanosheets on ITO coated glass substrate for preparation of working electrode for photoelectrochemical type photodetector. Vertical alignment of MoS2 nanosheets on substrate offers high surface-to-volume ratio, enhancing the electrochemical charge transport. MoS2 nanosheets based working electrodes shows obvious photovoltaic effect with photocurrent of 0.5 μA/cm2 at zero bias under 670 nm light of power intensity 100 mW/cm2. Maximum photoresponsivity of 170 μA/W, IPCE of 3 × 10−2% is realised owing optimized conditions. Overall, present finding advocates the development of large area, transparent and photosensitive electrode for PEC type photodetection application for visible light.

Performance evaluation of self-mixing interferometer with the ceramic type piezoelectric accelerometers

Abstract In this article, reconstructed displacement from the self-mixing signal is compared with the displacement obtained by the ceramic shear mode design piezoelectric accelerometer. Piezoelectric accelerometers are widely accepted due to the low output noise and wide frequency range, but nevertheless it is not contact-free. Self-mixing interferometric signals due to the vibrating target on which an accelerometer is attached are acquired by an external silicon type photodetector. The laser light hits directly the accelerometer as a target which is driven by the sum of two different sinusoidal frequencies of 150 and 300 Hz with different voltage levels.

A Facile Approach for Elemental-Doped Carbon Quantum Dots and Their Application for Efficient Photodetectors.

The present work demonstrates a facile hydrothermal approach to synthesize lanthanide-doped carbon quantum dots (CQDs) with europium and/or gadolinium elements. Taking the advantage of broadband adsorption in the ultraviolet-visible region, the doped QDs are directly used as building blocks for photo-electrochemical (PEC)-type photodetectors (PDs) and their performance is systematically investigated under various conditions. The europium (Eu) and gadolinium (Gd) co-doped (C:EuGd) QDs exhibit better photo-response than the single-elemental doped ones and also show outstanding long-term stability. According to the apparent response to light from 350 to 400nm, the C:EuGd QDs are demonstrated to hold great potential for narrow-band PDs. This work highlights the practical applications of lanthanide-doped CQDs for PDs, and the results are beneficial for the development of elemental-doped CQDs in general.