Photoelectric Response Characteristics Research Articles

Genetic algorithm-aided design of broadband near-perfect absorber with MoS2 film in the visible region

Broadband absorption plays a crucial role in the applications of optoelectronic devices. In this paper, we employ a genetic algorithm (GA) approach to enhance the absorption characteristics of an absorber comprising a MoS2 film enclosed within an antireflective coating and a one-dimensional Au grating supported by a gold mirror. An average absorptivity of 97.1 % is achieved for the optimized structure in the visible range (corresponding to wavelengths ranging from 400 nm to 800 nm). Finite element methods (FEM) and electromagnetic field analysis indicate that cavity resonances (CRs) and localized surface plasmon (LSP) resonances lead to absorption throughout a broad wavelength band. In addition, we verify the improved photoelectric response characteristics of the proposed absorber, which are significantly higher than the reference structures. Our approach is of importance for designing high-performance optoelectronic devices in the fields of photodetectors, modulators, solar energy and so on.

Perovskite single-pixel detector for dual-color metasurface imaging recognition in complex environment

Highly efficient multi-dimensional data storage and extraction are two primary ends for the design and fabrication of emerging optical materials. Although metasurfaces show great potential in information storage due to their modulation for different degrees of freedom of light, a compact and efficient detector for relevant multi-dimensional data retrieval is still a challenge, especially in complex environments. Here, we demonstrate a multi-dimensional image storage and retrieval process by using a dual-color metasurface and a double-layer integrated perovskite single-pixel detector (DIP-SPD). Benefitting from the photoelectric response characteristics of the FAPbBr2.4I0.6 and FAPbI3 films and their stacked structure, our filter-free DIP-SPD can accurately reconstruct different colorful images stored in a metasurface within a single-round measurement, even in complex environments with scattering media or strong background noise. Our work not only provides a compact, filter-free, and noise-robust detector for colorful image extraction in a metasurface, but also paves the way for color imaging application of perovskite-like bandgap tunable materials.

Fast solvent evaporation of phase pure CuBi2O4 photocathodes for photoelectrocatalytic water splitting

P-type metal oxide semiconductor CuBi2O4 exhibits excellent energy band structures and photoelectric response characteristics, which are critical for photoelectrocatalytic water splitting. However, the photocurrent densities are still well below the theoretical limit due to poor charge carrier separation and transport properties. In this work, we report a synthetic method for the preparation of phase-pure CuBi2O4 photocathode films via spray pyrolysis by adjusting the evaporation rate of the atomized droplets. An increase in the evaporation rate of the solvent may fix the structure of the deposited film faster and decrease the time available for the establishment of the segregation gradient, thus producing phase-pure semiconductor films. This method reduces process complexity and cost, and the applicability of spray pyrolysis for the preparation of phase-pure CuBi2O4 films is also confirmed. In addition, the photoelectrochemical evaluation of the samples prepared under different treatment conditions reveals that hole transport critically affects the photoelectrocatalytic performance of CuBi2O4 photocathodes. CuO can be used as a hole transport layer to promote the collection and transfer of holes and reduce the recombination of photogenerated carriers.

Investigating wide spectrum photoelectric response characteristics of PbS quantum dots/silicon nanowires array core-shell structure

Investigating wide spectrum photoelectric response characteristics of PbS quantum dots/silicon nanowires array core-shell structure

Effects of iron impurities on the photoelectric response characteristics of silicon.

Since Fe contamination is easily mixed into Si-based photoelectric materials during the fabrication process, the relative changes of energy levels and photoelectric properties of Si material mixed with Fe impurities in different occupancy sites are studied. Based on the first principle and photoelectric response theory, an analysis model of the response characteristics of Si material mixed with Fe impurities is established. The changes of the material's electronic structure are calculated, and the effects of different occupancy sites of Fe impurities on the photoelectric response characteristics of materials are comparatively analyzed. Results show that when the Fe atom occupies the tetrahedral interstitial site in Si, the energy band structure and response characteristics of the material are relatively obviously affected. In this case, the impurity energy band introduced by the Fe impurity passes through the Fermi level, leading to the disappearance of the band gap. The absorption of Si material outside the response band is significantly enhanced. And a new absorption peak is generated at about 1530nm, with an absorption coefficient of about 25513 cm-1. Thus, the Si material can produce a relatively strong response to the light beam outside the response band. In the meantime, the saturation threshold of the Si-based photoreceptor is significantly lower than that of the other two position types. For the irradiation light at the wavelength of 1319nm, the saturation power is only 0.0035 W∙cm-2. The analysis results provide a reference for the application and development of photoelectric devices.

Effects of Mg Component Ratio on Photodetection Performance of MgGa2O4 Solar‐Blind Ultraviolet Photodetectors

Mg x Ga2O4 epitaxial films with different Mg component ratios (x = 0.6, 0.8, 1, 1.1, and 1.4) and their metal–semiconductor–metal solar‐blind ultraviolet (SBUV) photodetectors are prepared on c‐face sapphire by metal–organic chemical vapor deposition (MOCVD). The structure, composition, crystalline quality, and optical properties of the Mg x Ga2O4 thin films have been investigated in detail. It can be found that five Mg x Ga2O4 thin films have the spinel structure with a similar bandgap of ≈5.15 eV, and the highest crystalline quality is observed in Mg x Ga2O4 with x = 1. Besides, photodetector based on Mg x Ga2O4 film with x = 1 has the highest responsivity, the largest UV–visible rejection ratio, and the fastest response speed. As the content of Mg deviates from the stoichiometric ratio of MgGa2O4, the crystalline quality of the Mg x Ga2O4 thin film is reduced, and their photoelectric response characteristics are deteriorated. This work indicates that MgGa2O4 is a promising candidate for the applications in high‐performance solar‐blind ultraviolet photodetectors.

Soil Respiration of Paddy Soils Were Stimulated by Semiconductor Minerals.

Large quantities of semiconductor minerals on soil surfaces have a sensitive photoelectric response. These semiconductor minerals generate photo-electrons and photo-hole pairs that can stimulate soil oxidation–reduction reactions when exposed to sunlight. We speculated that the photocatalysis of semiconductor minerals would affect soil carbon cycles. As the main component of the carbon cycle, soil respiration from paddy soil is often ignored. Five rice cropping areas in China were chosen for soil sampling. Semiconductor minerals were measured, and three main semiconductor minerals including hematile, rutile, and manganosite were identified in the paddy soils. The identified semiconductor minerals consisted of iron, manganese, and titanium oxides. Content of Fe2O3, TiO2, and MnO in the sampled soil was between 4.21–14%, 0.91–2.72%, and 0.02–0.22%, respectively. Most abundant semiconductor mineral was found in the DBDJ rice cropping area in Jilin province, with the highest content of Fe2O3 of 14%. Soils from the five main rice cropping areas were also identified as having strong photoelectric response characteristics. The highest photoelectric response was found in the DBDJ rice cropping area in Jilin province with a maximum photocurrent density of 0.48 μA/cm2. Soil respiration was monitored under both dark and light (3,000 lux light density) conditions. Soil respiration rates in the five regions were (from highest to lowest): DBDJ > XNDJ > XBDJ > HZSJ > HNSJ. Soil respiration was positively correlated with semiconductor mineral content, and soil respiration was higher under the light treatment than the dark treatment in every rice cropping area. This result suggested that soil respiration was stimulated by semiconductor mineral photocatalysis. This analysis provided indirect evidence of the effect semiconductor mineral photocatalysis has on the carbon cycle within paddy soils, while exploring carbon conversion mechanisms that could provide a new perspective on the soil carbon cycle.

Bidirectional Bias Response Ultraviolet Phototransistors With 4H-SiC NPN Multi-Layer Structure

Silicon Carbide (SiC) Ultraviolet (UV) phototransistors with bidirectional bias response were fabricated and analyzed in this letter. The results showed that the fabricated UV phototransistor exhibited stable photoelectric response characteristics and transistor characteristics under both forward and reverse voltages, owing to the structure design of the epi-layers, while the mechanism of the bidirectional response was also studied. The difference in photocurrent under different bias voltages and wavelengths of UV illumination were mainly due to the variation of the absorption coefficient with wavelength and the change in the width of the space charge regions, which ultimately led to a difference in the number of photo-generated carriers. The time response characteristics of the detector showed that there were time delays when the detector was turned on and turned off, which was caused by the photo minority carriers in the depletion layer of the base-collector junction.

Study on Graphene Field Effect Tube Photoelectric Sensor

As a special device that converts the measured physical quantity into electrical signal or other signal output according to specific rules, the sensor becomes the nerve ending connecting the natural world and the electronic world. Photoelectric sensors, as an important branch of sensors, play a central role in applications such as optical communication, imaging and detection, as electronic systems perceive external eyes. At present, the main sensor products in the market have defects such as limited detection wavelength, low responsivity and complex structure. In view of these problems and practical needs, combined with the advantages of graphene with wide detection wavelength range, high influence and high electron mobility, this paper proposes a graphene field effect tube photoelectric sensor with silicon nitride protective layer, and its preparation process, environmental stability test and photoelectric response characteristics are studied and analyzed. The results have potential application value. Graphene field effect transistor photoelectric sensor has many excellent characteristics, such as wide detection band, high response, good environmental stability and easy preparation and integration. It provides a new research idea for MEMS photoelectric sensor and has a very broad application prospect.

Research on near infrared photoelectric response and surface-enhanced Raman scatteringof urchin-like Au-Ag-Pt-Pd nanoalloy

Compared with the single metal, multi-metallic nanoparticle has excellent localized surface plasmon resonance with a wide spectral range response, which is beneficial to improving both the photoinduced electron transfer efficiency and the effective electron-hole separation. In this work, the urchin-like Au-Ag-Pt-Pd nanoalloy (Au-Ag-Pt-Pd NU) with multiple tentacles is successfully synthesized by the seed growth method and chemical reduction method. And we explore the optical properties of Au-Ag-Pt-Pd NU at different annealing temperatures. The results show that the transient photocurrent intensity of Au-Ag-Pt-Pd NU annealed at 200 ℃ is 1.6 times that of the primitive Au-Ag-Pt-Pd NUs at 808 nm excitation. In addition, the SERS signal intensity of crystal violet (CV) adsorbed on the Au-Ag-Pt-Pd NUs annealed at 200 ℃ is 1.8 times that of the primitive Au-Ag-Pt-Pd NUs at 785 nm excitation. For the Au-Ag-Pt-Pd NUs in this work, the concentration of CV can be detected to be as low as 10<sup>–12</sup> M. Furthermore, the interesting NIR-SERS sensor enables the detection limit of H<sub>2</sub>O<sub>2</sub> at low concentration to reach 0.09–1.02 μmol/L. The results show that the obtained nanoalloy has excellent photoelectric response characteristics and high SERS sensitivity due to the synergistic effect of multi-metal. Thus, it possesses great potential for biological NIR detection in the future.

Synthesis and photoelectric properties of SnSe films through selenization of evaporated Sn-metal films

Sn precursor layer was evaporated on a glass substrate by an electron-beam evaporation method and followed by selenization using Se powder. SnSe film was successfully prepared by adjusting the selenization temperature and selenization time. The phase, microstructure and optical properties of the SnSe films were studied by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy, and UV-Vis-NIR spectrophotometer. The results demonstrated that the pure phase polycrystalline SnSe films with a band gap of 0.93 eV could be prepared by selenizing at 450[Formula: see text]C for 60 min. Under the irradiation of a 980 nm laser with a power of 2 mW/cm2, photoelectric response characteristics of the SnSe films were tested, and the response time and recovery time of the prepared film were 62 ms and 80 ms, respectively, indicating that the SnSe film had a large application prospect in near-infrared light detection.

Photoelectric response characteristics of a novel translucent one-dimensional MAPbI<sub>3</sub>·DMF single crystal material

<p indent=0mm>Organic halide perovskites have broad application prospects in photoelectric detector due to their excellent photoelectric properties. Moreover, there has been growing interest in applying halide perovskites to semitransparent photovoltaics to achieve the highest combination of transparency and efficiency. In this paper, we aimed to prepare high-performance materials which are suitable for translucent optoelectronic devices using new preparation methods and explore the potential properties of these materials. We successfully synthesize a type of translucent linear MAPbI₃·DMF single crystal material with controllable size and good stability in atmospheric environment using the anti-solvent method. Toluene, which is often used as one of the surfactants to control the morphology of the perovskite films, was used as an anti-solvent in this paper. The growth of the one-dimensional (1D) single crystal wires was regulated by the control of the adsorbed toluene molecular at the interface, promoting the [PbI₆]⁴⁻octahedral unit in the precursor to assemble into a chain structure along the 1D direction. In addition, we could control the width and length of the single crystal wires via a slow cooling process. The width can reach tens of microns, and the length of the single crystal wires can be the centimeter level. The crystal structure of the transparent wire was analyzed using single crystal X-ray diffraction (XRD). The material exhibited a good 1D chain structure with an infinitely extended single edge-sharing octahedral lead halide chain {PbI₃}⁻ surrounded by CH₃NH₃⁺ (MA) and <italic>N</italic>,<italic>N</italic>-dimethylformamide (DMF). Through XRD characterization of the crystal structure after keeping the material at room temperature in air (~25°C, humidity ~40%) for a long time, we found that the single-crystal wire showed good stability in air. In addition, <italic>in situ </italic>heating XRD and <italic>in situ</italic> heating transmission electron microscopy (TEM) analyses showed that the morphology and crystal structure of the semi-transparent perovskite remained stable at 90°C, indicating that this material has good thermal stability. Further, an ultraviolet-visible absorption spectroscopy test showed that this material could absorb photons at <sc>300–800 nm,</sc> indicating that the obtained single crystal wire could absorb both ultraviolet and visible light. The material also exhibited a strong transmission effect for photons with wavelengths ranging from 500 to <sc>784 nm,</sc> indicating that the material has the semi-transparent property. According to the absorption spectrum, the transparency was calculated, and it was found that the transparency of single crystal materials increased in the range of more than <sc>500 nm,</sc> further implying that they have excellent translucence properties. Photoluminescence (PL) spectrum test showed that the single crystal material could emit <sc>~780 nm</sc> of fluorescence under laser irradiations of 409 and <sc>633 nm.</sc> Furthermore, using the Tauc plot method, we determined that this material has a bandgap of <sc>~1.58 eV,</sc> which is consistent with the PL test. In addition, this material shows good responsivity <sc>(7.13 A W^–1)</sc> with a response time of <sc>9.95 ms,</sc> making it suitable for photodetector applications. The good stability and photoelectric properties make this linear single crystal material an ideal candidate for the core absorbent layer of semi-transparent photodetector devices. This research work is expected to provide a reference for the development of transparent perovskite materials with high stability and good photoelectric properties.

Graphene Directly Growth on Non-Metal Substrate from Amorphous Carbon Nano Films Without Transfer and Its Application in Photodetector

A layer of nano amorphous carbon was fabricated on the target substrate by precisely controlled magnetron sputtering, and then a layer of copper film was fabricated on the amorphous carbon. By using a vertical cold wall chemical vapor deposition system under protective atmosphere, the carbon atoms at high temperature was catalyzed by copper to form graphene films. The amorphous carbon nano thin film was converted into monolayer graphene on a SiO2 substrate directly. The experimental results show that the graphene film has high crystal quality and conductivity. Compared with other methods, the process is simple and the process window is wider. By virtue of this technique, a graphene-Si photodetector was also demonstrated. The photoelectric response and frequency characteristics have been studied which shows good device characteristics.

The research progress of Si-based blocked-impurity-band infrared detecting materials and detectors

<p indent=0mm>Infrared detection possesses a significantly application prospect in the field of astrophysics. Due to the special natures of deep-space exploring objects, the performance of infrared detector is very demanding. Blocked-impurity-band (BIB) infrared detectors, with advantages of wide spectrum coverage, low noise, high sensitivity, good resistance to cosmic particle radiation etc., have become the state-of-the-art choice for astronomical application internationally. The response of BIB detectors ranges from mid-infrared to far-infrared waveband, and the widespread use of BIB detectors help human beings obtain a series of important scientific achievements in the field of deep-space exploration. The research on BIB infrared detector in China started rather late. Even though big progress has been achieved in recent years, it still lags far behind the advanced level globally. This article reviews the research progress for BIB infrared detectors of China in the past <sc>5 years.</sc> The preparation technology, physical property characterization, photoelectric response characteristics of BIB infrared detection material and corresponding devices, and the control of surface plasmon polaritons on the photoelectric response of the detectors are introduced detailly. These provide references and experimental bases for the development of BIB infrared detector in China.

Preparation of a CaFe2O4/ZnCo2O4 composite material and its photocatalytic degradation of tetracycline

Abstract In this paper, a two-step method was used to successfully construct a CaFe2O4/ZnCo2O4 composite photocatalyst. XRD, TEM, XPS, PL, EIS, etc., were used to characterize the morphological structure, element state, photoelectric response and other characteristics of the material. Tetracycline (TC) was used as the target pollutant to evaluate the photocatalytic performance of the composite photocatalyst. The results showed that in the best reaction system (ZC-30), the TC degradation rate reached 88% within 100 min of light exposure, while that in the CaFe2O4 system was only 17%. The TC degradation rate with ZC-30 is 11.26 times and 2.21 times higher than that with CaFe2O4 and ZnCo2O4, respectively. The main reason is that the close contact between CaFe2O4 and ZnCo2O4 can effectively separate and transfer the light-induced carriers, which improves the photocatalytic activity of the catalyst. The SEM and XRD results and the cycling experiments results confirmed that the synthesized photocatalyst showed good stability after 3 cycles. CaFe2O4/ZnCo2O4 can be used for oxytetracycline and chlortetracycline degradation with a good degradation rate. Moreover, the composite photocatalyst was systematically studied in the TC degradation system to analyze the possible TC degradation pathway, the effective active substances and a reasonable catalytic mechanism.

Measurement and Correction Model for Temperature Dependence of an Acousto-Optic Tunable Filter (AOTF) Infrared Spectrometer for Lunar Surface Detection.

The photoelectric response characteristics of an infrared spectrometer based on an acousto-optic tunable filter (AOTF) are greatly affected by the temperature change of the radio frequency power amplifier and shortwave infrared detector. If calibration is not conducted, that will affect the quantitative level of the data. This paper puts forward a measurement and correction method for the temperature characteristics of an AOTF infrared spectrometer which is used in lunar surface detection and sets up a temperature characteristics correction model. This model was applied to an AOTF infrared spectrometer mounted on China's unmanned lunar rover. Laboratory tests show that the temperature causes an instrument variation of ∼20% when the temperature is between -20 ℃ and + 55 ℃, but this model reduces this variation to < 6%. Evaluating data from the lunar surface also verifies the effectiveness of this method.

Preparation of superhydrophobic CdS cotton using visible light response and its application for the control of water pollution

Sewage discharge produced by homes and industries contains both oil and water-soluble components. In order to remove oil from water, materials with specific wettability can be used; however, these materials cannot remove dissolved contaminants from water. In this research, we prepared a superhydrophobic CdS cotton for water purification. This material has the ability to adsorb different types of oil due to its non-wettability (WCA = 152°). Moreover, its response behavior towards visible light enables it to remove water-soluble pollutants as well. The highest oil absorption rate of superhydrophobic CdS cotton is nearly 30 times, and it can absorb light below 564 nm and produce •OH to degrade water soluble pollutants. Finally, based on Mott-Schottky curve, the position of Fermi energy level was determined (–0.55 eV). Also, the positions of valence and conduction bands were calculated based on the analysis of band gap which helps in proving photoelectric response characteristics.

Chemical vapor deposition all-inorganic CsPbI2Br perovskite nanofibers for photodetector

Chemical vapor deposition method can prepare perovskite films with controllable morphology and adjustable photoelectric properties. In this work, we have prepared CsPbI2Br films at 400 °C–700 °C using chemical vapor deposition method. The grain size of perovskite film increases with the deposition temperature increment because higher temperature provides greater driving force for nucleation expansion. CsPbI2Br film deposited at 600 °C shows nanofiber structure with polycrystalline property accompanied by local single crystal structure. Steady-state and time-resolved fluorescence measurement explored the charge carrier recombination process of perovskite films. The photodetector based on CsPbI2Br film deposited at 600 °C shows excellent photoelectric response and switching ratio characteristics. This is ascribed to low defect density and fast charge transport along 1D fiber channels.

Facile synthesis of Ti3+ self-doped and sulfur-doped TiO2 nanotube arrays with enhanced visible-light photoelectrochemical performance

Titanium dioxide nanotube arrays (TiO2 NTAs) has shown its promising properties for use as a photoelectrode material. However, the efficiency in this regard is restricted by the wide band gap of TiO2. In this study, a facile method was employed to prepare Ti3+ self-doped and sulfur-doped (S-doped) TiO2 NTAs (H-S-TiO2 NTAs). The Ti3+ and S co-doping greatly improved the photoelectrochemical performances of TiO2 NTAs. The optimized H-S-TiO2 NTAs showed obviously red-shifted compared with the optimized TiO2 NTAs. The saturation photocurrent density and the photoelectric conversion efficiency of the optimized H-S-TiO2 NTAs reached 1.97 mA/cm2 and 1.18%, which were 3.72 and 4.92 times higher than that of the optimized TiO2 NTAs, respectively. Furthermore, the optimized H-S-TiO2 NTAs exhibited the highest transient photocurrent density (1.08 mA/cm2) with excellent photoelectric response characteristics, indicating that the transfer efficiently of photogenerated carriers was increased in the optimized H-S-TiO2 NTAs. On the basis of research results, such enhanced performances could prove that the Ti3+ self-doping and S-doping had synergistic effects. The established S-doping as well as introduced Ti3+ self-doping of TiO2 NTAs resulted in enhanced visible-light absorption and rapid electron transfer rate.

Covalent organic framework as an efficient, metal-free, heterogeneous photocatalyst for organic transformations under visible light

Visible-light active, heterogeneous, and organic photocatalysts exhibit a more sustainable and environmentally friendly alternative to classical metal-based catalysts. Two-dimensional covalent organic frameworks (2D-COFs) with permanent porosity, columnar π-arrays and excellent stability, that can become an excellent platform for heterogeneous photocatalysis of organic transformations. Here we report a predesigned imine-based COF with electron donor and acceptor structure. And new framework possesses large surface area, high crystallinity, outstanding stability and broad absorption range in the visible-light region as well as good photoelectric response characteristics. Importantly, it was found to be a highly effective heterogeneous photocatalyst for reductive dehalogenation of phenacyl bromide derivatives and α-alkylation of aldehydes under irradiation of visible-light. In addition, the COF gave good recyclability and could be reused after a simple separation manipulation. The current present still reveals a great prospect for 2D-COFs as metal-free, heterogeneous photocatalysts for organic transformations.