Photoelectric Measurements Research Articles

Designs, Synthesis, Characterization and Direct Electrochemistry of Zinc‐Porphyrin Bearing Pyrene Noncovalent Functionalized Graphene Oxide Sheet

AbstractWe have designed and synthesis a new compound of zinc‐porphyrin bearing four pyrene groups (ZnP‐t‐P(py)4) and prepared a new hybrid materials of ZnP‐t‐P(py)4 with graphene oxide (GO) via non‐covalent interactions. The ZnP‐t‐P(py)4, along with four pendant pyrene entities ZnP‐t‐P(py)4, stacking on the (GO) surface due to π‐ π interactions, has been revealed by AFM measurements. FTIR, UV‐vis absorption confirm the non‐covalent functionalization of the GO. Raman spectral measurements revealed the electronic structure of the GO to be intact upon hybrid formation. In this donor‐acceptor nanohybrid, the fluorescence of photoexcited ZnP‐t‐P(py)4 is effectively quenched by a possible electron‐transfer process. The fluorescence and photoelectrical response measurements also showed that this hybrid may act as an efficient photoelectric conversion material for optoelectronic applications.

Synthesis of ZnTe dendrites on multi-walled carbon nanotubes/polyimide nanocomposite membrane by electrochemical atomic layer deposition and photoelectrical property research

We report on the electrochemical atomic layer deposition (EC-ALD) of ZnTe dendrites on the carboxyl-functionalized multi-walled carbon nanotubes/polyimide (COOH-MWCNTs/PI) membrane. Electrochemical characteristics were studied by cyclic voltammetry (CV) and the deposition of ZnTe dendrites was completed using amperometric method (I–t). The prepared ZnTe dendrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The growth mechanism of ZnTe dendrites was elucidated to give a deep understanding of crystal growth. The concentration of reagents and deposition cycle had a significant effect on the morphology and structure of deposits. UV–vis transmission study indicated a direct band gap of 2.26eV. Photoelectrical measurement confirmed the p-type conductivity of ZnTe dendrites, which indicated that the dendritic ZnTe crystals may have potential practical application in optoelectronic devices.

Click‐Functionalized Ru(II) Complexes for Dye‐Sensitized Solar Cells

AbstractThree heteroleptic ruthenium complexes incorporating new ancillary ligands synthesized by sequential connection of different alkyl functionalities with triazole as a linker are prepared using click chemistry. These sensitizers exhibit low‐energy metal‐to‐ligand charge transfer bands centered at 540 nm with molar extinction coefficients of up to 1.54 × 104 L mol−1 cm−1. The devices using these sensitizers in conjunction with a volatile electrolyte show high photovoltaic conversion efficiencies of 8.7 to 9.9% under standard AM 1.5G sunlight (100 mW cm−2) conditions. Using an ionic liquid electrolyte, the cells show not only a good power‐conversion efficiency of up to 7.1%, but also promising long‐term stability under full sunlight intensity at 60 °C. The difference in the photovoltaic parameters during the ageing process is investigated by employing transient photoelectrical measurements.

Light controlled assembling of iodine-free dye-sensitized solar cells with poly(3,4-ethylenedioxythiophene) as a hole conductor reaching 7.1% efficiency

We report the fabrication of indoline D205 dye-sensitized solar cells (DSSCs) with photoelectrochemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) as a hole conductor. Different from conventional photoelectrochemical polymerization under continuous spectral light illumination (e.g. Xe lamp), we conduct the polymerization under monochromatic light. The device performance is found to be dependent on the wavelength of monochromatic light used for the polymerization of PEDOT. Under optimized conditions, the efficiency of DSSCs reaches 7.1%, which is better than that of devices fabricated via continuous spectral light illumination. Detailed characterization of these devices with photoelectrical and impedance measurements reveals that the wavelength of monochromatic light affects PEDOT penetration into TiO2 porous electrodes and photoelectron recombination at the FTO surface. The best device performance is obtained when penetration and recombination are optimized.

Preparation and Characterization of Nano‐Polyaniline Film on ITO Conductive Glass by Electrochemical Polymerization

Polyaniline (PANI) films were synthesized on a conducting ITO glass by potentiostatic techniques to construct a low‐cost counter electrode for dye‐sensitized solar cell (DSSC). The compact layer, nanoparticles, nanorods‐ and fibrils were observed on the top of PANI films with different constant potentials by SEM. Then the conductivity test illuminated that a polyaniline film with the highest conductivity was electrodeposited at 1.0 V. Finally, the photoelectric measurement showed that the energy conversion efficiency of DSSC with the PANI electrode was increased with the potential decreasing. And the efficiency of DSSC with PANI counter electrode at 1.0 V was higher than that with Pt electrode, owing to the high surface area, high conductivity, and excellent catalytic activity of PANI electrode. Therefore, the PANI counter electrode with excellent catalytic performance is a potential substitute for platinized electrode to save cost of DSSC.

Concentration of uncompensated impurities as a key parameter of CdTe and CdZnTe crystals for Schottky diode xγ-ray detectors

In this paper we report on the strong impact of the concentration of uncompensated impurities on the detection efficiency of CdTe and Cd0.9Zn0.1Te Schottky diodes. The results of our study explain the observed poor detection properties of some Cd0.9Zn0.1Te detectors with resistivity and lifetime of carriers comparable to those of good CdTe detectors. We show that the concentration of uncompensated impurities in a highly efficient CdTe Schottky diode detector is several orders of magnitude higher than that of a CdZnTe, which does not register the gamma spectra of commonly used isotopes (59–662 keV) by using photoelectric measurements. The significant difference of the concentration of uncompensated impurities between CdTe and Cd0.9Zn0.1Te crystals is confirmed by our study of the temperature change of the resistivity and of the Fermi level energy. The degree of compensation of the donor complex, responsible for the electrical conductivity of the material, is much lower in the CdTe crystal compared to that in the Cd0.9Zn0.1Te crystal. The calculations of the detection efficiency of x/γ-radiation by a Schottky diode result in a dependence on the concentration of uncompensated impurities described by a curve with a pronounced maximum. The position of this maximum occurs at a concentration of uncompensated impurities which ranges from 3 × 1010 to 3 × 1012 cm−3 depending on the registered photon energy of x/γ-rays and on the lifetime of the charge carriers. Our measurements and calculations lead to the conclusion that the concentration of uncompensated impurities in this range is a necessary condition for the effective operation of x- and γ-ray Schottky diode detectors based on CdTe and Cd1−xZnxTe crystals.

Band diagram determination of MOS structures with different gate materials on 3C-SiC substrate

AbstractMOS capacitors were fabricated on 3C-SiC n-type substrate (001) with a 10-μm N-type epitaxial layer. An SiO2 layer of the thickness tOX ≈55 nm was deposited by PECVD. Circular Al, Ni, and Au gate contacts 0.7 mm in diameter were formed by ion beam sputtering and lift-off. Energy band diagrams of the MOS capacitors were determined using the photoelectric, electric, and optical measurement methods. Optical method (ellipsometry) was used to determine the gate and dielectric layer thicknesses and their optical indices: the refraction n and the extinction k coefficients. Electrical method of C = f(VG) characteristic measurements allowed to determine the doping density ND and the flat band voltage VFB in the semiconductor. Most of the parameters which were necessary for the construction of the band diagrams and for determination of the basic physical properties of the structures (e.g. the effective contact potential difference ϕMS) were measured by several photoelectric methods and calculated using the measurement data. As a result, complete energy band diagrams have been determined for MOS capacitors with three different gate materials and they are demonstrated for two different gate voltages VG: for the flat-band in the semiconductor (VG = VFB) and for the flat-band in the dielectric (VG = VG0).

Ruthenium Sensitizer with Thienothiophene-Linked Carbazole Antennas in Conjunction with Liquid Electrolytes for Dye-Sensitized Solar Cells

A new heteroleptic ruthenium complex, coded CYC-B12, incorporating an antenna ligand composed of sequential connections of a thienothiophene conjugated bridge and carbazole hole-transport moiety was prepared. This new sensitizer exhibits a lower energy MLCT band centered at 555 nm with a high molar absorption coefficient of 2.24 × 104 M–1 cm–1. The device sensitized by CYC-B12 in conjunction with a volatile electrolyte shows a high photovoltaic efficiency of 9.4% under an illumination of standard global AM 1.5G sunlight. With a low-volatile electrolyte, the cell based on this new sensitizer shows not only a good conversion efficiency of 8.2% but also excellent durability (>96%) under light soaking at 60 °C in a simulated sunlight for 1000 h. The difference in the electron recombination kinetics caused by various liquid electrolytes or aging process is also investigated by employing the transient photoelectrical measurements.

Preventing Dye Aggregation on ZnO by Adding Water in the Dye-Sensitization Process

ZnO based dye-sensitized solar cells have been studied using N719 and Z-907 as sensitizing dyes, with and without including water to the dye solution. The solar cells have been characterized with photoelectric measurements and the interface between the dye and the ZnO surface has been studied using photoelectron spectroscopy. It was shown that water in the dye solution greatly reduces surface dye aggregation and thereby enhances the solar cell performance for N719. For Z-907 where no sign of dye aggregation could be found, the presence of water had minor effect on the surface structure and solar cell performance.

Charge propagation dynamics at trapping centers that induce the luminescence of rare-earth dopants in wide-gap materials

For rare-earth doped semiconductors, charge propagation from semiconductors to rare-earths is essential for excitation of optically active dopants. However, the qualitative model that has been widely accepted to describe this process is based upon indirect evidence; in this model, it is believed that trapping and subsequent recombination of the charges at some rare-earth-related defect excite the dopants. In this work, we observe the sequential process directly, and quantify the trapped charge density and relaxation frequency using a photoelectric measurement technique for samarium-doped titanium dioxide with intense visible luminescence under ultraviolet light.

Electrical and Photoelectrical Characteristics of the ZnO/Organic Hybrid Heterostructure

The characteristics of the p-n heterojunction between vertically aligned ZnO nanowires and a Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) thin film were investigated. The current-voltage characteristics of the structures had a very good rectifying diode-like behavior with a leakage current less than 5.39 × 10−7 A at -2 V, a breakdown voltage greater than 10 V, and a forward turn-on voltage of 1 V. In addition, the effects of ultraviolet (UV) illumination and temperature on the I-V characteristics of the ZnO/PEDOT:PSS configuration were also investigated. The photoelectric measurements demonstrated that the photodiode had a high sensitivity and selectivity to UV light.

Stress state around cracks on the boundary of a hole in a photoelastic orthotropic plate under creep

The stress–strain state near cracks on the boundary of a circular hole in a linear elastic orthotropic composite plate under tension is analyzed. The distribution of stress intensity factors (SIFs) at the crack tip is found from photoelectric measurements. The dependence of the SIFs on the ratio of crack length to hole radius and on the mechanical properties of the material is established

Photoinduced processes in chromophore–gold nanoparticle assemblies

Development of nanotechnology requires that the interaction between components of nanoscale devices can be studied and understood better. Photoinduced processes between small (2–5 nm in core diameter) gold nanoparticles (GNPs) and chromophores, including porphyrin, fullerene, and phthalocyanine, were studied. Two methods were selected for controlled assembly of chromophores and gold particles at close distances: thin films and covalent attachment, which yields chromophore-functionalized particles. Time-resolved spectroscopic and photoelectrical measurements carried out further confirmed the known strong effect of GNPs on photoexcited chromophores that leads to fast photoinduced processes. When GNPs are combined with suitable chromophores, the particles can act as electron donors or acceptors. GNPs are efficient energy acceptors, and some indications of their ability to act as energy donors were obtained. The participation of the GNPs in photoinduced charge transfer in addition to energy-transfer processes makes them attractive components for photoactive devices.

Electrical and photoelectrical measurements on ZnO-Nanowires coated with PEDOT:PSS for Dye-Sensitized Solar Cells

ABSTRACTDye-sensitized solar cells composed of an n-doped ZnO nanowire array and a p-doped polymer layer appears to be a promising candidate for low-cost production of environment-friendly solar cells. In this work, we investigate hybrid devices consisting of a transparent conducting oxide (TCO) substrate, ZnO-nanowires (ZnO-NW) or a sol-gel prepared ZnO layer, a ruthenium dye (N719) and a PEDOT:PSS or P3HT layer. The dense polycrystalline ZnO layer is able to prevent short circuits, which have a strong effect on the performance of the solar cells. This is demonstrated by the use of only the ZnO layer which improves the open circuit voltage by a factor of 2 and the efficiency by a factor of 1.7 compared to cells with nanowires. That indicates that the system combined with a thin but dense ZnO layer and NW grown on it will show further improvement. Furthermore three different TCO substrates were investigated. Impedance spectroscopy (IS) reveals at least one additional Schottky barrier formed with ZnO:Al substrates. Spectral photovoltage measurements clearly show distinct absorption features correlated with the ZnO and N719 dye.

多光谱多光轴设备光轴平行性测量装置研制

Parallelism calibration apparatuses equipped with multispectral and multi axial system are extensively used for the calibration and measurement of parallelism among detection units in the small multi-sensor photoelectric measurement equipment,meanwhile provide infinite targets for detection units.A sort of multispectral and multi axial calibration apparatus with Cassegrain reflective collimator are researched,its effective aperture is φ350 mm,may measure the optical-axis parallelism among visible light system,middle infrared system,long wave infrared system and laser distance measuring system,measuring accuracy is better than 5″.

Anomalies in the Temperature Dependence of the Photoelectrical Response of GaAs/InGaP Superlattices

Photoelectrical measurements were taken on InGaP (p+)-GaAs/InGaP-InGaP (n+) multilayers structures, formed by a sequence of nominally undoped InGaP/GaAs quantum wells, interposed between two p+ and n+ InGaP cladding layers. The heterostructures were grown through Low Pressure Metal Organic Vapour Phase Epitaxy, with liquid precursors for the III–V elements and growth conditions optimized for obtaining sharp interfaces and negligible ordering effects in InGaP. The experimental temperature dependence of the photoelectrical signal intensity exhibited peculiarities and anomalies which could lead to erroneous analysis of the perpendicular transport mechanisms, so that they are here critically discussed in the light of a partial depletion of the nominally intrinsic superlattice region of the p–i–n structure.

Low cost method to obtain counter electrode for dye sensitised solar cells

In this paper, nanoscaled polypyrrole particles were synthesised using I2 as dopant and oxidant, which were subsequently used to prepare polypyrrole/epoxy resin composition counter electrode for construction of dye sensitised solar cells (DSSCs). The results of photoelectric properties measurement revealed that the open-circuit voltage Voc was 0·525 V, short circuit current density Jsc was 0·90 mA cm–2, fill factor FF was 0·45 and overall energy conversion efficiency η was 0·22% respectively. The introduction of polypyrrole/epoxy resin counter electrode decreased the demand of fluorine doped tin oxide (FTO) coated glass substrate of DSSCs, which proposed a novel idea for the development of counter electrodes.

The investigation of structural, electrical, and optical properties of thermal evaporated AgGaS 2 thin films

AgGaS 2 (AGS) thin films were deposited onto glass substrates by sequential thermal evaporation of AgGaS 2 single crystalline powder and excess silver (Ag) interlayer. Systematic optimization to obtain single phase AgGaS 2 thin films was carried out by changing the thickness of the excess silver layer. The structure and composition of as-grown and annealed films were studied by means of X-ray diffraction and energy dispersive X-ray analysis, respectively. The optical properties of AGS thin films determined by transmittance and reflection measurements showed that they had quite high absorption coefficient with the values around 10 4 (cm −1). The calculated band gap values were found to be between 2.30 and 2.75 eV depending on annealing temperature. The refractive index ( n) and extinction coefficient ( k) of the films were determined by the envelope method. Finally, photo-electrical measurements under different illumination intensities were carried out, and different sensitizing and recombination centers were defined.

Growth of thin epitaxial alumina films onto Ni(111): an electron spectroscopy and diffraction study

AbstractAn epitaxial ultra‐thin alumina layer was prepared on Ni(111) by simultaneous Al deposition and oxidation at elevated temperatures. Different deposition procedures lead to creation of oxide layers of various thicknesses and quality. Low‐energy electron diffraction revealed epitaxial parameters of the films and the relationship between the nickel substrate and the oxide overlayer. Core‐level photoelectron spectroscopy using Al‐Kα and synchrotron‐generated photons show that the oxide‐metal interface is formed by oxygen atoms, which is contrary to the case of epitaxial alumina layers prepared by the oxidation of NiAl(110) and Ni3Al(111) surfaces. The results of a photoelectric work function measurement are also discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Interpretation of the light curve for the young binary (?) system UY Aur

Using visual, photographic, and photoelectric measurements, we have constructed a historical light curve for the young binary system UY Aur on an interval longer than 100 yr. About a quarter of all magnitude estimates have been obtained for the first time from photographic plates of the Sternberg Astronomical Institute and Harvard College Observatory Astronomical Plate Stacks. Analysis of the light curve and the magnitude dependences of the polarization and color has led us to the following conclusions. Cyclic variations in the seasonally mean brightness of the binary’s primary component UY Aur A with a period of ≃16.3 yr occurred from the mid-1920s to the mid-1940s and after 1986. The variations are caused by the change in the rate of disk accretion onto the star attributable to the motion of the hypothetical companion UY Aur C around the primary star in an orbit with a semimajor axis of ≃ 6 AU. From the early 1950s to the mid-1980s, the periodicity of the seasonally mean variations was not noticeable due to nonperiodic eclipses of UY Aur A by gas-dust clouds. Between 1945 and 1974, another gas-dust cloud obscured and still obscures the component UY Aur B, causing its mean optical brightness to drop by several magnitudes. The role of the clouds that caused an almost simultaneous eclipse of the stars, whose separation in projection onto the celestial sphere exceeds 100 AU, is played by the denser and puffed-up regions of their accretion disks. These regions are the result of a dynamical interaction between the binary’s stars and the outer circumbinary accretion disk. The extinction variations with time are attributable to orbital motion of the binary’s stars and azimuthal inhomogeneity of the clump regions in the disks. A number of observational tests are suggested to verify our conclusions.