Photoelectric Field Research Articles

Hydrothermal synthesis and controlled growth of group-VIB W metal compound nanostructures from tungsten oxide to tungsten disulphide.

Two-dimensional lateral group-VIB transition metal dichalcogenides (TMDs) have attracted much attention in the fast evolving field of advanced photoelectric functional materials, but their controllable fabrication is challenging. Herein, an emerging synthetic route for sulfurization of tungsten oxide was developed. During the hydrothermal reaction, the optimization of the precursor selection and synthesis parameters led to the tunable properties of WO3-WSxOy-WS2 nanostructures. The vulcanization was thermodynamically favorably at low temperatures and in an environment with a sufficient S source, wherein WO3 was reduced by H atoms to WO3-x, and S atoms were preferentially adsorbed on O vacancies. The WSxOy nanostructures have a narrow band-gap attributed to the effect of S on the valence band top and electronic density of states by density functional theory. The photocurrent response and charge transfer properties of WSxOy were improved due to the charge transport between WS2 and WO3. Understanding the formation and transformation of WS2 nanostructures in solution contributes to the discovery of the important structure-efficiency relationship, which may be extended to other TMDs systems. Hence, extensive research efforts are still needed to develop safer and more efficient synthesis and modification methods to fully utilize the distinctive advantageous properties of TMDs in the photoelectric field.

Crystalline-Induced Luminescence of Carbon Dots for the WLED and Fingerprint Recognition

It is profound to obtain simply carbon nanodots (CDots)-based solid-state fluorescent in photoelectric field. However, synthesizing such material is still faced with a challenge due to the serious quenching effect. Here, a microwave pyrolytic route is reported to rapidly synthesize sulfur (S) and nitrogen (N) co-doping CDots wrapped by the crystalline phthalate (CDots/PA). The results show that CDots/PA presents needle-like crystal to coat abundant cluster of CDots inside, after fully optimizing the preparation conditions. The solid state CDots/PA emits a dazzling fluorescence with the fluorescence quantum yield (FLQY) [Formula: see text]%, which is attributed to the formation of barrier from the crystal to avoid the aggregation of CDots. In addition, due to the co-doping of S and N elements, it also presents an orange–red light with a multipeak feature. The excellent photoluminescence (PL) property of CDots/PA gives it an advantage to fabricate light emitting diode (LED)/white light emitting diode (WLED) devices, which achieves an orange light with the correlated color temperature [Formula: see text][Formula: see text]K, color rendering index [Formula: see text] and a warm-white light with the CCT [Formula: see text] 3700[Formula: see text]K, CRI [Formula: see text] 82 at the Commission Internationale de L’Eclairage [Formula: see text], 0.40) combined with the commercial phosphors. Moreover, CDots/PA also shows an excellent recognition capacity in the application of detecting latent fingerprints, endowing such fluorescent nanomaterials broad prospect in the photoelectric industry.

Air-stable CsPbIBr<sub>2</sub> photodetector via dual-ligand-assisted solution strategy

The CsPbIBr<sub>2</sub> perovskite films deposited from the precursor solutions in air, usually suffer poor surface coverage and air-stability due to the uncontrolled nucleation and the existence of I<sup>–</sup> during the film formation, resulting in terrible photoelectric characteristics and reproducibility. At present, the high-quality CsPbIBr<sub>2</sub> films are prepared under nitrogen atmosphere, which results in the increase of the cost and thus impedes their applications in air. Here in this work, we propose a strategy for growing the perovskite films with low defect density and better stability in air via dual-ligand-assisted (ligand 1 (LP) and ligand 2 (NH<sub>4</sub>SCN)) solution strategy. These ligands contain some organic molecules which have strong interaction with ions on the surface of perovskite thin film in order to regulate the addition of precursor ions onto the films. The high-quality CsPbIBr<sub>2</sub> thin films are prepared in air with relative humidity of ≤60% by the spraying method. The results indicate that ligand 1 with hydrophilic group and hydrophobic group, a kind of surfactant, can effectively reduce the surface tension of perovskite precursor solution, improve the coverage of CsPbIBr<sub>2</sub> perovskite film, and form a block layer of water and oxygen. However, the addition of ligand 1 in precursor solution inevitably introduces many grain boundaries, which is unfavorable for carrier transport and collection. Thus, ligand 2 is employed to control the nucleation of perovskite film as another ligand, resulting in reducing the point defect formation. Their combination is beneficial to forming the uniform perovskite film with large-size crystal and low-density defect. The high-quality crystallization of the perovskite film is found to simultaneously enhance the response and the durability of photodetectors. Thus, the unpackaged photodetectors (ITO/CsPbIBr<sub>2</sub>/Au) based on this strategy yield the outstanding photoelectric response under the excitation of 405 nm laser. This device exhibits a low dark current density of 2 × 10<sup>–4</sup> mA/cm<sup>2</sup>, a fast response time of 20–21 µs, and high stability (81%, ≥70 d) in air with a relative humidity of 40%–60%. Hence, this study provides a simple method to prepare high-quality CsPbIBr<sub>2</sub> perovskite thin films with low-density defect and realize air-stable and charge-transport-layer-free CsPbIBr<sub>2</sub> photodetectors for practical applications in photoelectric detection field.

SnSe/SnS: Multifunctions Beyond Thermoelectricity

Miniaturization, lightweight and highly integration have gradually become the main trends in the development of modern science and technology. Two-dimensional (2D) SnSe/SnS-based materials have recently received widespread attention in the field of thermoelectricity because of the remarkable physical transport properties. However, the peculiar crystal structure also ensures that SnSe and SnS materials can meet the requirements of the miniaturized and highly integrated functional devices, which make them the most notable interdisciplinary hotpots. In this review, we initially analyzed the basic physical properties and outlined the important achievements in thermoelectric field of SnSe/SnS. With the development of preparation technology for thin-film materials and nanomaterials, SnSe/SnS has been successfully utilized in multiple fields, including photothermal, photoelectric and ferroelectric fields. We then elaborated the multifunctions in SnSe/SnS, such as solar cells, photodetectors, photocatalysis, etc. Eventually, some personal summaries and prospects are demonstrated, which might highlight the importance of multifunction and promote the potential applications of 2D materials including SnSe/SnS.

Enhancement of photoluminescence of monolayer transition metal dichalcogenide by subwavelength TiO<sub>2</sub> grating

Transition metal dichalcogenide (TMDC) monolayers have direct band gaps and can produce strong photoluminescence(PL), thereby possessing a wide application prospect in photoelectric devices and photoelectric detection fields. However, their PL efficiency needs further improving because they are of atomic thickness only, besides, they have non-radiative recombination of excitons. In this study, a combination structure of a gold film, titanium dioxide subwavelength gratings and TMDC monolayers is designed, which can greatly improve PL efficiency of the TMDC monolayers. The spontaneous emission rate can be controlled by the Purcell effect, and the maximum enhancement of photoluminescence is as high as 3.4 times. In this paper, the PL signals of monolayer WS<sub>2</sub> and monolayer WSe<sub>2</sub> on the designed structure are studied. The feasibility of the enhancement of PL of the TMDC monolayers on the subwavelength grating structure is verified experimentally, which provides a new idea for the application of two-dimensional materials to optoelectronic devices.

Ultrasensitive photodetectors based on graphene quantum dot-InSe mixed-dimensional van der Waals heterostructures

Combining the advantages of GQDs and InSe, GQD/InSe 0D–2D MvdWH-based photodetectors with a responsivity of 27.48 A W−1 and a detectivity of 1.2 × 1012 Jones are proposed.

First principles study of photogalvanic effect of monolayer SnS

The photogalvanic effect of monolayer SnS was investigated at a small bias voltage under perpendicular irradiation using density functional theory combined with the non-equilibrium Green’s function method. The photocurrent was generated over the entire visible light range, and it was saturated at a small bias voltage for photon energies of 2.4, 2.6, 3.2 and 3.4 eV. The photocurrent shows cosine dependence of the polarization angle, which is attributed to the second-order response to the photoelectric field. These results provide a deeper understanding of the photogalvanic properties of the 2D SnS nanosheet based devices.

Ultrahigh Aggregation Induced Emission Efficiency in Multitwist-Based Luminogens under High Pressure.

Increasing aggregation induced emission (AIE) efficiency is of fundamental interest as it directly reflects performance of multitwist-based luminogens in bioimaging and in the photoelectric device field. However, an effective and convenient methodology to increase AIE efficiency significantly remains a challenge. Here, we present a general strategy to increase AIE efficiency of multitwist-based luminogens by pressure, resulting in a 120.1-fold enhancement of the AIE intensity of tris[4-(diethylamino)phenyl]amine (TDAPA) under high pressure compared to that of the traditional method. AIE efficiency of TDAPA increases from 0.5% to 46.1% during compression. Experimental and theoretical investigations reveal that the AIE efficiency enhancement originates from intramolecular vibration and the twisted intramolecular charge transfer are suppressed under high pressure. High AIE efficiency under high pressure provides an important inspiration for improving performance of multitwist-based luminogens in the lighting and biomedical fields.

Optimization Preparation of Indium Tin Oxide Nanoparticles via Microemulsion Method Using Orthogonal Experiment

Indium tin oxide (ITO), an experimentally friendly transparent conducting oxide (TCO), has attracted great attention in the photoelectric field due to its intrinsically low resistivity and high transparency. In this work, the experimental conditions of preparing ITO nanoparticles using the microemulsion method were optimized by an orthogonal experiment. The optimal experimental conditions were obtained: mass ratio of the surfactant (AEO-3, MOA-5), a co-surfactant (n-propyl alcohol) of 5:3, molar ratio of indium and ammonia of 1:20, calcination temperature of 700 °C and calcination time of 4 h. Subsequently, the influence from process variables on the resistivity was researched systematically. The results demonstrated that the calcination temperature had a great effect on the resistivity; the resistivity reduced from 11.28 to 2.72 Ω·cm with the increase in the calcination temperature from 500 to 700 °C. Ultimately, ITO nanoparticles were prepared and systematically characterized under the optimal experimental conditions. The particles with a size of 60 nm were attributed to the cubic ITO crystal phase and showed low resistivity of 0.3675 Ω·cm. Significantly, ITO nanoparticles with low resistivity were obtained using the microemulsion method, which has potential application in the field of ITO nanoparticle preparation.

Double electric dipole moment contribution model of the Verdet constant of paramagnetic magneto-optical materials

Besides considering the influence of the transition dipole moment, the impact of the external magnetic field and photoelectric field on the electron’s movement is also taken into account by using forced vibration to correct the electric dipole moment, and a unique double electric dipole moment contribution model of the Verdet constant of paramagnetic magneto-optic materials is deduced. Using terbium gallium garnet (TGG) crystal as an example, various microscopic effects and energy levels splitting inside the paramagnetic magneto-optic materials are analyzed in detail. Then, the Verdet constant of TGG crystal under different theoretical models is quantitatively solved. Compared with current theories, the results calculated using the double electric dipole moment contribution model are more consistent with the experimental data, indicating that the model has certain advantages.

Photocurrent Enhancement of PtSe2 Photodetectors by Using Au Nanorods

Compact and highly sensitive near-infrared photodetectors that are operable at room temperature are required for light detection and ranging and medical devices. Two-dimensional (2D) PtSe2, a transition metal dichalcogenide, is a candidate material for near-infrared light detection. However, the photoresponse properties of 2D PtSe2 are currently inferior to those of commercial materials. The localized surface plasmon resonance of Au has been widely used for photoelectric field enhancement and in photochemical reactions associated with phase relaxation from plasmon states that occur at specific wavelengths. Spherical Au nanocolloids exhibit an extinction peak in the visible light region, whereas nanorods can be tuned to exhibit the extinction peak in the near-infrared region by controlling their aspect ratio. In this study, hybrid Au nanorod/2D PtSe2 structure was fabricated via spin coating nanorods, with plasmon peaks in the near-infrared region, on 2D PtSe2. Furthermore, the effect of the concentration of the nanorod solution on the photoresponse of nanorod/2D PtSe2 was investigated. The photocurrent of 5 nM Au nanorod-coated 2D PtSe2 was fivefold higher than that of bare 2D PtSe2. The responsivity was maximum 908 μW/A at 0.5 V bias voltage. In addition, the photocurrent enhancement mechanism by Au nanorods is discussed.

Synthesis and Applications of Functional Nanomaterials

The unique physical and chemical properties and variable application potential of nanomaterials are continuously devoted to stimulating scientists’ studying enthusiasm. Extremely fine grains bring quantities excellent properties such as low density, low elastic modulus, high resistance and low thermal conductivity to nanomaterials, which has extensive use in the photoelectric field, environment, bioengineering and other fields. The research progress of graphene quantum dots, transparent reflective coatings and self-assembled nanotubes are mainly demonstrated. This paper shows the role of graphene quantum dots in solar cells, summarizes the synthesis methods of self-assembled nanotubes and their applications in bioengineering, and describes the development of transparent thermal reflective coatings for energy-saving glass attributed to providing relevant reference and basis for the development and research of nanomaterials.

Harmonic dual-wavelength and multi-soliton pattern fiber laser based on GO-Sb2Se3 saturable absorbers

As new two-dimensional materials, antimony selenide (Sb2Se3) and graphene oxide (GO) are ideal photoelectric materials due to their appropriate band gap structure and strong light-matter interaction, which can be used in optical modulators, broadband ultrafast optical switches, and other photoelectric fields. The GO and Sb2Se3/GO measurements show excellent nonlinear characteristics with the modulation depth of 3.18% and 4.78%, respectively. This work proposes a harmonic dual-wavelength (HDW) fiber laser based on GO. This provides new possibilities for the research of ultrashort pulse sources with both high repetition frequency and multiple wavelengths. Furthermore, the conventional soliton mode-locking with 984 fs pulse width and soliton bundles mode-locking is obtained. The Sb2Se3/GO SA is coupled into the laser cavity for the first time to achieve higher performance mode-locked pulse. The results show that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as the pulse width is shortened from 984 fs to 511 fs and the slope efficiency increased from 11.9% to 16.18%, which confirms its potential application in nonlinear optical material and ultrafast pulse generation. The results provide a new opportunity to apply traditional broadband nonlinear optical materials in ultrafast photonics and make a fundamental contribution to the development of advanced nanophotonic devices.

Antisolvent-Processed One-Dimensional Ternary Rubidium Copper Bromine Microwires for Sensitive and Flexible Ultraviolet Photodetectors.

Recently, newly emerging halide perovskites have aroused intensive attention in photoelectric fields in virtue of their good properties, such as well-balanced carrier transport, large light absorption coefficient, tunable band gap, and low-temperature solution processing technique. Nevertheless, their future commercial development is severely hampered by lead toxicity and instability of such materials. In this work, one-dimensional Rb2CuBr3 single-crystal microwires (MWs) were prepared by antisolvent engineering, and they were further employed as absorbers to prepare sensitive ultraviolet (UV) photodetectors. The optical band gap of Rb2CuBr3 MWs is measured to be 3.83 eV, exhibiting an excellent UV absorption. The fabricated device demonstrates a remarkable UV light detection ability with a specific detectivity of 1.23 × 1011 Jones, responsivity of 113.64 mA W-1, and response speed of 69.31/87.55 ms under light illumination of 265 nm. Meanwhile, the proposed photodetector without any encapsulation shows outstanding stability and repeatability. After storing in ambient air for 2 weeks, the light detection ability remains basically unchanged. Further, a flexible photodetector was fabricated with the same structure, which demonstrates a remarkable bending endurance. These results confirm the great potential of Rb2CuBr3 for high-performance UV photodetectors, increasing the possibility for assembly of optoelectronic systems.

Tunable Schottky Barrier and Interfacial Electronic Properties in Graphene/ZnSe Heterostructures.

With a direct bandgap, two-dimensional (2D) ZnSe is a promising semiconductor material in photoelectric device fields. In this work, based on first-principles methods, we theoretically studied the modulation of the Schottky barrier height (SBH) by applying horizontal and vertical strains on graphene/ZnSe heterojunction. The results show that the inherent electronic properties of graphene and ZnSe monolayers are both well-conserved because of the weak van der Waals (vdW) forces between two sublayers. Under horizontal strain condition, the n(p)-type SBH decreases from 0.56 (1.62) eV to 0.21 (0.78) eV. By changing the interlayer distance in the range of 2.8 Å to 4.4 Å, the n(p)-type SBH decreases (increases) from 0.88 (0.98) eV to 0.21 (1.76) eV. These findings prove the SBH of the heterojunction to be tuned effectively, which is of great significance to optoelectronic devices, especially in graphene/ZnSe-based nano-electronic and optoelectronic devices.

MXene Core-Shell Nanosheets: Facile Synthesis, Optical Properties, and Versatile Photonics Applications

In recent years, the transition metal carbonitrides(MXenes) have been widely applied to photoelectric field, and better performance of these applications was achieved via MXene complex structures. In our work, we proposed a MXene core-shell nanosheet composed of a Ti2C (MXene) phase and gold nanoparticles, and applied it to mode-locked and single-frequency fiber laser applications. The optoelectronic results suggested that the performances of these two applications were both improved when MXene core-shell nanosheets were applied. As a result, we obtained a mode-locking operation with 670 fs pulses, and the threshold pump power reached to as low as 20 mW. Besides, a single-frequency laser with the narrowest linewidth of ~1 kHz is also demonstrated experimentally. Our research work proved that MXene core-shell nanosheets could be used as saturable absorbers (SAs) to promote versatile photonic applications.

Construction stable and highly bright photoluminescence of Ag and Mn codoped Zn-In-Se nanocrystals toward wLEDs application

Quantum dots (QDs) with composition/size dependent optoelectronic properties have been regarded as emerging materials to be potentially applied in photoelectric fields. For QDs based light emitting diodes (QDLEDs), the efficient devices are still focused on toxic binary QDs containing heavy metals. Herein, a series of less-toxic and emission color tunable Ag, Mn codoped Zn-In-Se optimized dQDs are synthesized and detailed studied via the facile low-cost one-pot hot-injection synthetic method using Se in octadecene as ‘green’ Se source. After coating a thick ZnSe shell (~7.9 monolayers) on the core dQDs, higher photoluminescence (PL) quantum yield (QY) up to 68% was achieved and higher emission efficiency was retained even when the initially oil-soluble QDs are transferred into aqueous media by ligand replacement. Furthermore, both photostability and thermal stability of the core/shell dQDs were significantly enhanced as compared with those of core dQDs due to the suppressed surface defects resulting from the passivation of the dense ZnSe layers. The dQDs are further applied in QDLEDs as singly emitter and exhibited good performance with color rendering index (CRI) of 79, CIE coordinates of (0.368, 0.327), CCT of 4105 K and maximum luminance of 180 cd m−2, indicating that the studied core/shell dQDs could be a potential candidate in QD-based lighting or solid-state lighting as a single color-converting materials.

(C7H18N2)PbI4: A 2D Hybrid Perovskite Solid-State Phase Transition Material with Semiconducting Properties.

Two-dimensional organic-inorganic hybrid perovskites (OIHPs) have gained attention as a result of their flexibility and adjustability of the structure. However, the large band gap of two-dimensional perovskites limits their application in the photoelectric field. In the present work, we report a two-dimensional organic-inorganic hybrid compound of (C7H18N2)PbI4 (1) with a narrow band gap, which consists of [PbI4]2-n layers and N-(2-aminoethyl)piperidinium cations. 1 exhibits semiconducting properties with a narrow optical band gap of ∼2.02 eV and a photoelectric response with a ratio of photocurrent to dark current of ∼100. In addition, it exhibits a reversible solid-state phase transition at 228 K. This finding should inspire research into more 2D layered OIHPs with the combination of phase transition and semiconductor properties.

High-performance electrochemiluminescence emitter of metal organic framework linked with porphyrin and its application for ultrasensitive detection of biomarker mucin-1

Mucin-1, an essential transmembrane glycoprotein, was regarded as a promising biomarker for colon, breast, ovarian and lung cancers. Thus, its highly sensitive and selective detection is important to develop new analytical strategies. In this work, Zn-based metal organic frameworks with pyridine (Zn-Bp-MOFs) were synthetized via coordination to enhance the ECL responses of zinc meso-tetra(4-sulfonatophenyl) porphine (Zn-TP). The synthesized Zn-Bp-MOFs substantially accelerated the electrocatalytic reduction of K2S2O8 and excited electron amount of Zn-TP. For that, the Zn-TP linked Zn-Bp-MOFs (terminated as Zn-TP@Zn-Bp-MOFs) displayed 32-fold magnification in the ECL efficiency relative to free Zn-TP. By assembly of capture DNA (cDNA), functional luminophore effectively captured the released linked DNA (L-DNA) from double-stranded DNA (dsDNA, hybridization of aptamer DNA (aptDNA) and L-DNA) via the strong interactions between the aptDNA and mucin-1. Consequently, thionine was implanted into the groove of newly-formed dsDNA and severely quenched the ECL intensity of the emitter. The resulting biosensor showed wide linear range from 1 pg mL-1 to 10 ng mL-1 with a limit of detection (LOD) as low as 0.23 pg mL-1. Hence, such MOFs hold substantial promise to broaden their applications in photoelectric detection field.

Photo-electric capacitive deionization enabled by solar-driven nano-ionics on the edges of plasma-made vertical graphenes

Unimpeded ion traffic in carbon materials with ionic selectivity remains a challenge in electrochemical energy storage and chemical purifications represented by capacitive deionization (CDI) of potable and industrial water. In this work, a new concept of solar nano-ionics is developed to directly feed solar energy into photocarriers and localized electric fields near the edges of graphene nanostructures that enable effective, mobility-based ion transport with high mass exchange rates and selectivity. This concept is applied to demonstrate the new approach for CDI, namely the photo-electric capacitive deionization (PECDI), enabled by the solar-enhanced ionic transport. Materialized by edge-enhanced vertical graphenes (eVG), the photocarriers are localized along the edge nano-antennas of eVG to boost the edge-localized electric fields by two orders of magnitude, as confirmed by near-field photo-induced force microscopy. The localized photo-electric fields control and restructure the nano-ionic flows leading to selective transport of ions with different mobility and dramatically enhanced kinetics, as validated by in situ electrochemical quartz crystal microbalance measurements and molecular dynamics simulations. With the photo-enhanced ionic transport kinetics, an average adsorption capacity of 33 mg g−1 at 200 mg L–1 (165 mg g−1 at 5000 mg L–1), a fast adsorption/desorption response and the impressive efficiency are achieved. This work opens a new avenue for solar-enhanced nano-ionic manipulation, which can be extended for a broad range of chemical engineering, energy, and environmental applications.