Photoelectric Measurements Research Articles

Fabrication of PEDOT:PSS/ZnO:S based hybrid heterostructures and their photoelectrical characteristics

Sulfur doped ZnO nanorods were synthesized through a simple, low-cost, and low temperature hydrothermal route. The influence of sulfur doping on the material properties of ZnO were studied using scanning electron microscopy (SEM) and Raman spectroscopy. The density of defects states associated with ZnO was found to increase on sulfur doping through the photoluminescence measurements from the visible band emissions. The current–voltage characteristics on the fabricated PEDOT: PSS/SZO heterojunction diodes were found to exhibit excellent rectifying characteristics under dark and illumination conditions. The photoelectric measurements demonstrated that sulfur doping leads to significant improvements in the photo electronic performances of the corresponding hybrid hetero-structures.

Field-Effect Phototransistors Based on Graphene-Quantum Dot Hybrids

Field effect photo-transistors (FEpTs) based on graphene-PbSe quantum dot (QD) hybrids have been designed and fabricated. By electrical and photoelectrical measurements, the carrier mobilities reached to 1621 cm 2 V -1 s -1 for electrons and 1228 cm 2 V -1 s -1 for holes, the photoresponsivity (R) achieved to 1 AW -1 , and the photoresponse time (τ 1 ) was 0.7 s when the photocurrent came to about 80%. Therefore, the FEpTs based on graphene-QD hybrids have shown broad application prospects.

The Study of Full-Size Objects’ Bistatic Rader Cross Section Measurement Based on Photoelectric Conversion

In the past years, bistatic Radar Cross Section (RCS) characteristic has been caught increasing attention. The paper presents a bistatic RCS measurement system of full-size goals, which uses photoelectric conversion technology to solve the problem that excessive electrical signal attenuation exits because of the large distance between sending and receiving antenna. The paper analyzes the basic principle of photoelectric conversion and RCS measurement system, applies photoelectric conversion technology to RCS measurement system, and tests whether RCS measurement system works well while using photoelectric conversion technology. The test results show that the system can efficiently obtain the bistatic RCS characteristic of full-size targets.

光电测量设备图像高频频谱对主观评价的影响

光电测量设备图像高频频谱对主观评价的影响

Synthesis, crystal structure, electronic structure, and photoelectric response properties of KCu2SbS3.

Copper thioantimonates have received enormous attention due to their potential for applications in photovoltaic devices. In this work, a new layered compound KCu2SbS3 was synthesized via a reactive flux method using thiourea as a reactive flux. The compound crystallizes in the triclinic space group P1[combining macron]. The structure features two-dimensional [Cu2SbS3](-) layers stacking along the c axis with K(+) ions intercalated between the layers. Each [Cu2SbS3](-) layer is composed of two single graphene-like layers connected via interlayer Cu-S bonds and CuSb contacts. The optical measurements indicate that the compound has a band gap of 1.7 eV. The Hall effect measurement shows that KCu2SbS3 is a p-type semiconductor with a carrier concentration of 7 × 10(16) cm(-3). First-principles calculations reveal that the direct transition occurs between Cu-3d-S-3p orbitals (VBM) to Sb-5p-S-3p orbitals (CBM). The photoelectric response properties of KCu2SbS3 under visible light irradiation were analyzed. The photocurrent is 3.7 μA cm(-2) at 10 V bias, demonstrating its potential for applications in photoelectric devices.

BiOI/Bi12O17Cl2: A novel heterojunction composite with outstanding photocatalytic and photoelectric performances

A novel BiOI/Bi12O17Cl2 heterojunction composite was fabricated via a facile deposition–precipitation method. The surface loading of a portion of BiOI strongly broadened the visible light absorption of Bi12O17Cl2 from 500–600nm. The photoelectric performance measurements show that the tightly contacted BiOI/Bi12O17Cl2 heterojunction largely strengthened the spatial separation efficiency of photocharges under visible light. Furthermore, BiOI/Bi12O17Cl2 applying to degrade two contaminant models, methyl orange (MO) and phenol, displayed much higher photocatalytic activity than the single Bi12O17Cl2 and BiOI under visible light (λ>400nm). This is a successful Bi-based semiconductor composite photocatalytic system that can efficiently remove the organic contaminants in wastewater.

Enhanced performance of PbPc photosensitive organic field effect transistors by inserting different-thickness pentacene inducing layers

Lead phthalocyanine (PbPc) based photosensitive organic field effect transistors (PhOFETs) with different-thickness pentacene inducing layers (INLs) inserted between SiO2 and PbPc layer were fabricated and characterized. The photoelectric measurements demonstrate that the device with 2-nm-thick pentacene INL exhibits the largest photoresponsivity of 505.75mA/W and maximum photo/dark current ratio of 405.35 in all devices. For this, we give an overall explanation that different-thickness INLs display different continuity and crystallinity and thus produce strong or weak template inducing. Especially, when the INL thickness (δ) is 2nm a quasi-continuous and highly crystalline approximate-monolayer INL forms on SiO2 surface, which may play a strong role of template inducing, thus causing its upper PbPc film to demonstrate the strongest triclinic (300) line and the strongest NIR absorption in series PbPc films. When δ=1nm, pentacene does not form a continuous film. And when δ=5 or 10nm, a continuous multilayer INL with a declined crystallinity due to possible lattice mismatch forms on SiO2 surface and gives a weakened template inducing. Thereby, it can be recognized that inserting a pentacene INL can markedly enhance the performance of single layer PbPc PhOFET and the optimum INL thickness is proved ∼2nm in present conditions.

Characterization of a‐Se p–i–n junction fabricated using bidirectional electrolysis in NaCl(aq)

In this article, we introduce an electrochemical doping method of amorphous selenium (a‐Se) using NaCl(aq). Recently, an a‐Se photovoltaic device fabricated using this method [I. Saito, W. Miyazaki, M. Onishi, Y. Kudo, T. Masuzawa, T. Yamada, A. Koh, D. Chua, K. Soga, M. Overend, M. Aono, G. A. J. Amaratunga, and K. Okano, Appl. Phys. Lett. 98, 152102 (2011)] has been announced and opened up the potential of a new impurity doping method. This study will further explore its possibilities by doping chlorine (Cl) and sodium (Na) and aim to fabricate a p–n junction by reversing the applied voltage during the electrolysis. The device is characterized through photoelectric measurements. The I–V characteristics show rectification under light illumination.

Photogeneration process in bulk heterojunction solar cell based on quaterthiophene and CdS nanoparticles

In this paper, the blended systems composed of organic oligothiophenes and CdS nanoparticles were investigated through their optical and photoelectrical measurements for their potential applications in photovoltaic devices. The electrical and photoelectrical properties of the devices fabricated with the active layer sandwiched between the metal anode and the metal cathode have been reported. Dependence of the performance of this bulk heterojunction photovoltaic device on their composition has been investigated with respect to charge transport. The organic/inorganic interface area in bulk heterojunction is an important factor in the photovoltaic process. The incorporation of nanoparticles in the polymer matrix, for the purpose to fabricate hybrid inorganic–organic materials, could be a good alternative to enhance the charge generation process of free carriers. The J–V curves of the quaterthiophene (4T) and hybrid quaterthiophene/cadmium sulfide nanoparticles CdS show the important role played by the nanoparticles for energy conversion improvement. The experimental data were found to be in good agreement with a modified Braun–Onsager model.

Behavior of the Fe impurity in Hg3In2Te6 crystals

Optical and photoelectric measurements reveal that doping with iron leads to the formation of a deep level at Ec–0.69 eV in Hg3In2Te6 crystals. When light is absorbed by Fe2+ impurity centers, both electronic transitions of the impurity-level–conduction-band type and optical transitions between ground and excited states of the aforementioned centers (intracenter transitions) are observed. Investigations of transport phenomena point to the acceptor properties of Fe2+ centers.

Photo electrical and optical anomaly in ferromagnetic cobalt doped ZnO nanostructures

For the development of novel devices, the correlation of oxygen vacancies and room temperature ferromagnetism in cobalt doped zinc oxide nanostructures synthesized by Co precipitation route reported earlier Zia et al (2014 Phys. Scr. 89 105802) has been further explored on the basis of structural, optical, magnetic and photoelectrical measurements. In the current study, x-ray diffraction data is further exploited for the measurement of d-spacing, c-direction growth for the plane (002) and cell volume. Increased volume of the unit cell is observed with the increase in cobalt content. UV–visible absorption spectroscopy analysis reveals the reduction in optical energy band gap with the increase in cobalt concentration. The saturated and remanence magnetization were found to be increasing with cobalt addition during the magnetic analysis. The photoelectrical conductivity has maximum value for the sample Co (3% mol) and least recovery time as compared to Co (0% mol). The sensing response was found to be decreasing with the addition of cobalt. The anomalies in the photoelectric parameters clearly reflect the presence of photoconductive nature, which may have ramifications for device engineers.

Synthesis, Crystal Structure, and Photoelectric Properties of a New Layered Bismuth Oxysulfide.

[Bi2O2]-containing tetragonal compounds have received enormous attention due to unique functions including ferroelectricity, photocatalysis, and superconductivity. Here, a new layered compound Bi9O7.5S6 was synthesized via a facile hydrothermal route. The compound, belonging to a new structure type crystallizes in a rhombohedral system with space group R3̅m (a = 4.0685(1) Å, c = 31.029(5) Å, V = 444.8(1) Å(3), Z = 1). The overall crystal structure consists of alternatively packed unique [Bi2O2] and [BiS2] layers along [001] which are combined with each other by van der Waals interaction. The phase purity of the product is confirmed by powder X-ray diffraction. XPS analyses indicate +3 for Bi and -2 for S atoms. The temperature dependence of resistivity ρ(T) indicates that the semiconducting sample follows the mechanisms of variable range hopping (VRH) and adiabatic small polaron hopping (SPH). The direct-transition band gap, Eg = 1.27 eV derived from optical absorption spectrum, falls in the optimal region of solar absorber materials. Accordingly, the photoelectric measurement demonstrates the potential for applications for photovoltaic devices.

Effect of Arcing in Air on the Photoelectric Work Function of Silver-Based Contacts

In this paper, we report new photoelectric measurements that throw light on the effect of arcing in air on the electron work function (EWF) of contact pastilles made of pure silver [Ag (99.999%)], silver–nickel alloy [Ag–Ni (60/40)], silver–tungsten alloy [Ag–W (50/50)], and silver–tungsten carbide [Ag–WC (50/50)]. The influence of industrial treatment (polishing, mechanical shocks, and electrical arcs in air) of pure metals and silver–metal alloys on their EWF is experimentally investigated. To study the effects of arcing on the EWF, the metallic samples were subjected to electrical arcs in air, at atmospheric pressure, and room temperature, after that, they have been introduced into the vacuum chamber of an experimental ultrahigh vacuum setup for EWF measurements. Fowler’s method of isothermal curves was used for the measurement of the EWF by the photoelectric effect. Contacts were mounted in a contactor working repetitively in air (laboratory atmosphere). A cycle of arcing consisted in opening contacts on charging, with production of an electric arc with adjustable duration, and closing a few seconds after arc extinction at zero voltage. When subjected to 500 arcs, the EWF for Ag contacts is 4.50 ± 0.03 eV at room temperature, while for virgin Ag contacts, it was 4.30±0.03 eV. The increase in the EWF is due to the progressive inclusion of silver oxide in the Ag contact surface during arcing in air. The conditioned (500 arcs) silver–metal alloys studied in this paper exhibit the same electronic emission behavior, namely, arcing in air increases their EWF. We demonstrated that the electromechanical conditioning by successive electrical arcs affects the photo-EWF.

Synthesis and electrical properties of In2O3(ZnO)m superlattice nanobelt**Project supported by the National Natural Science Foundation of China (Grant No. 51172058), the Key Project of the Science Technology and Research Project of Education Bureau, Heilongjiang Province, China (Grant No. 12521z012), and the Natural Science Foundation of Heilongjiang Province for Returned Chinese Scholars, China (Grant No. LC2013C17).

One-dimensional (1D) In2O3(ZnO)m superlattice nanobelts are synthesized by a chemical vapor deposition method. The formation of the In2O3(ZnO)m superlattice is verified by the high-resolution transmission electron microscopy images. The typical zigzag boundaries could be clearly observed. An additional peak at 614 cm−1 is found in the Raman spectrum, which may correspond to the superlattice structure. The study about the electrical transport properties reveals that the In2O3(ZnO)m nanobelts exhibit peculiar nonlinear I–V characteristics even under the Ohmic contact measurement condition, which are different from the Ohmic behaviors of the In-doped ZnO nanobelts. The photoelectrical measurements show the differences in the photocurrent property between them, and their transport mechanisms are also discussed.

UV-induced SiC nanowire sensors

Ultraviolet (UV)-induced sensors based on a single SiC nanowire (NW) were fabricated and the photoelectric properties including I–V characteristics and time response of the UV sensors were studied. SiC NWs (NWs) were prepared through pyrolyzing a polymer precursor with ferrocene as the catalyst by a CVD route. To elucidate the physical mechanism giving rise to the photoelectrical response in SiC NW sensors, three kinds of contacts between electrodes and SiC NW were prepared, i.e. Schottky contact, p–n junction contact, and Ohmic contact. The photoelectric measurements of the device with Schottky contact indicates the lowest dark current and the largest photocurrent. The results suggest that photocurrent generated at SiC NW-electrode contacts is a result of the photovoltaic effect, in which a built-in electric field accelerates photo generated charge carriers to the electronic contacts. The UV sensors based on SiC NWs could be applied in a harsh environment due to the excellent physical stability and photoelectric properties.

Photo-Induced Doping in Graphene/Silicon Heterostructures

Photoinduced doping in graphene and its related heterostructures has drawn much interest as one of the possible ways to control the electronic properties of graphene. In this paper, we report that graphene/silicon (Gr/Si) heterostructures are an effective configuration for photoinduced doping in graphene. Raman spectroscopy, electrical and photoelectrical measurements are used to characterize the photoinduced doping effect. The results demonstrate that the graphene in the Gr/Si heterostructure is p-doped by light irradiation, and the doping effect can be controlled by varying the irradiation time. For the electrical properties of the Gr/Si Schottky junction, the photoinduced doping effect reduces the barrier height and series resistance but enhances the ideality factor. For the photovoltaic properties, the doping strengthens the open-circuit voltage, short-circuit current, fill factor, and conversion efficiency. The work should be helpful on developing effective ways for graphene doping and in depth understanding and better use of Gr/Si Schottky junctions for electronics and optoelectronics.

Effects of CH3NH3I on fabricating CH3NH3PbI(3-x)Clx perovskite solar cells

Perovskite solar cell, which is prepared by using the organic-inorganic hybrid halide CH3NH3PbX3 (X = I, Cl and Br), receives widespread attention because of its solution processability and high photon-to-electron conversion efficiency. The highest reported photon-to-electron conversion efficiency is that using CH3NH3PbI(3-x)Clx as an absorber. It is reported that the diffusion length is greater than 1 micrometer in this mixed halide perovskite. The method most commonly used in preparing CH3NH3PbI(3-x)Clx film is the one-step pyrolysis method, which has a complex reaction mechanism. In this paper, we review the work about CH3NH3PbI(3-x)Clx perovskite, in which emphasis is put on the importance of the preparation process, and analyze the role of CH3NH3I in the one-step pyrolysis method for fabricating the CH3NH3PbI(3-x)Clxperovskite layer. Scanning electron microscope images show that CH3NH3I can improve the coverage and crystallinity of the perovskite layer for precursors in low CH3NH3I concentrations (CH3NH3I/PbCl2=2.0 and 2.5). For precursors in high CH3NH3I concentrations (CH3NH3I/PbCl2=2.75 and 3), this change is not obvious. X-ray photoelectron spectroscopy confirms the change of coverage, and indicates that the content of Cl in CH3NH3PbI(3-x)Clx will be less than 5% for precursors with high CH3NH3I concentrations (CH3NH3I/PbCl2>2.5). Perovskite solar cells based on CH3NH3PbI(3-x)Clx with different Cl dopant concentrations are studied by photoelectric measurements. Photocurrent density-photovoltage curves show that the performance of the devices increases with the increase of CH3NH3I concentration in precursors. And the incident-photon-to-current conversion efficiency (IPCE) measurements indicate that the devices fabricated by using precursors with high CH3NH3I concentration have a relatively high external quantum efficiency. These results imply that only CH3NH3PbI(3-x)Clx with very low Cl dopant concentration will be effective material for photovoltaic application. To further understand the difference between these devices during working condition, transient photovoltage/photocurrent measurements are carried out to investigate the carrier dynamics in the device. Transient photovoltage decay curves indicate that high Cl dopant concentration may decrease the photoelectron lifetime in CH3NH3PbI(3-x)Clx, and results in a relative low open-circuit photovoltage in the corresponding photovoltaic devices. The charge transport time in the devices of various Cl concentrations are studied by transient photocurrent decay method. CH3NH3PbI(3-x)Clx with low Cl dopant concentration has relative short transport time, which can avoid the recombination process and increase the charge collection efficiency.

Preparation of AgInS₂ quantum dot/In₂S₃ co-sensitized photoelectrodes by a facile aqueous-phase synthesis route and their photovoltaic performance.

In an aqueous-phase system, AgInS2 quantum dot (QD) sensitized TiO2 photoanodes were prepared in situ by the reaction of β-In2S3 nanocrystals and as-prepared TiO2/Ag2S-QD electrodes, followed by a covering process with a ZnS passivation layer. A facile successive ionic layer adsorption and reaction (SILAR) method was adopted to obtain TiO2/Ag2S-QD electrodes. β-In2S3 nanocrystals synthesized by the chemical bath deposition (CBD) process serve as the reactant of AgInS2 as well as a buffer layer between the interfaces of TiO2 and AgInS2-QDs. A polysulfide electrolyte and a Pt-coated FTO glass count electrode were used to test the photovoltaic performance of the constructed devices. The characteristics of the sensitized photoelectrodes were studied in more detail by electron microscopy, X-ray techniques, and optical and photoelectric performance measurements. AgInS2 is the main photo-sensitizer for TiO2/AgInS2-QD/In2S3 electrodes and excess In2S3 appears on the surface of the electrodes. Based on the optimal Ag2S SILAR cycle, the best photovoltaic performance of the prepared TiO2/AgInS2-QD/In2S3 electrode with the short-circuit photocurrent density (Jsc) of 7.87 mA cm(-2) and power conversion efficiency (η) of 0.70% under full one-sun illumination was achieved.

A Photoinduced Electron Transfer System by Graphene Oxide Non-covalently Linked Porphyrin Antennae in Water

Non-covalent interacting porphyrin/Graphene Oxide (GO) nanohybrids were formed in water and confirmed by TEM, Raman, FT-IR, XRD, UV-vis and fluorescence spectroscopy. The binding constant between porphyrin and GO is 2.38 × 103 L mol−1 calculated by Benesi-Hildebrand equation based on absorbance plot, which confirmed a robust porphyrin/GO nanohybrid formation. Fluorescence of porphyrin was effectively quenched by GO indicated the efficient photoinduced electron transfer (PET) from porphyrin moieties to GO, which porphyrin acts as energy absorbing and electron transferring antennae and GO serves as an efficient electron acceptor of the system. The photoelectrical response measurements of porphyrin/GO nanohybrid showed a rapid and reversible on/off photovoltage and photocurrent by the alternative white light. The PET from porphyrin to GO is energetically favorable deduced by calculating free Gibbs energy. Non-covalent porphyrin/GO nanohybrid may be used as photovoltaic conversion materials for photoelectronic applications.

Photoelectric Property Measurement of Organic Materials Based on TOF Method

The principle and experimental setup of photoelectric property measurement withTime of Flight (TOF) method are described. Si sample is used to affirm thevalidity of the experiment setup. The photoelectric property of MEH-PPVmaterials is measured and the mobility is accounted base on TOF method. Moreover,the attention items of using TOF method are proposed. The results consist well with the theoretical value.