Intensity-voltage Characteristics Research Articles

Revisiting Schottky barriers for CIGS solar cells: Electrical characterization of the Al/Cu(InGa)Se2 contact

Devices based on a metal‐semiconductor contact are potential candidates for the fabrication of photovoltaic cells as long as the corresponding junctions exhibit good rectifying properties and a low contact resistance. This article presents a detailed electrical analysis of the aluminum/CIGS system. The values of the representative parameters of the quality of the diode such as the barrier height, the ideality factor and the series resistance are deduced from an analytical study of the intensity‐voltage characteristics. It is concluded that this system does fulfill the necessary (but not sufficient) basic conditions for being used in photovoltaic cells.

Image Sensor System With Bio-Inspired Efficient Coding and Adaptation

We designed and implemented an image sensor system equipped with three bio-inspired coding and adaptation strategies: logarithmic transform, local average subtraction, and feedback gain control. The system comprises a field-programmable gate array (FPGA), a resistive network, and active pixel sensors (APS), whose light intensity-voltage characteristics are controllable. The system employs multiple time-varying reset voltage signals for APS in order to realize multiple logarithmic intensity-voltage characteristics, which are controlled so that the entropy of the output image is maximized. The system also employs local average subtraction and gain control in order to obtain images with an appropriate contrast. The local average is calculated by the resistive network instantaneously. The designed system was successfully used to obtain appropriate images of objects that were subjected to large changes in illumination.

Electro-optical and dielectric relaxation studies of an antiferroelectric liquid-crystal mixture (W-132A)

Electro-optical properties and dielectric relaxation phenomenon have been investigated for antiferroelectric liquid-crystal mixture W-132A exhibiting SmA*, SmC*, and wide temperature range (∼0–48°C) induced SmCA* phases. Spontaneous polarization, tilt angle, response time, viscosity, relaxation frequency, dielectric strength, and distribution parameter have been determined as a function of temperature. Switching process has been studied in the antiferroelectric SmCA* phase with the help of transmission intensity-voltage characteristics. Impedance spectroscopy of the material under the planar anchoring conditioning of the sample has been carried out in the frequency range of 1Hz–10MHz. Usual soft-mode dielectric relaxation in the SmA* phase and Goldstone mode in the SmC* phase have been observed. A tendency of the soft mode to penetrate into the SmC* phase and that of the Goldstone mode into the SmCA* phase have been observed. The dielectric spectrum of the SmCA* phase exhibits two absorption peaks, namely, PL and PH modes which are separated by about two decades of frequency. PL is related to in-phase azimuthal angle fluctuation of the molecules in antitilt pairs, whereas PH is due to the antiphase fluctuation of the molecules in antitilt pairs.

Extraction of electro-optic coefficient in thin-film linear electro-optic Mach-Zehnder interferometers with nonperiodic intensity-voltage output characteristics

The intensity-voltage output characteristics of thin-film linear electro-optic Mach-Zehnder interferometer modulators can be nonperiodic for configurations where the optic axis is perpendicular to the applied electric field. As a result, the electro-optic coefficient for the material can not be determined assuming a periodic half-wave voltage. From the Jones matrix calculation, an analytic expression of the output intensity is derived in terms of the phase retardation. A method of determining the linear electro-optic coefficient is proposed based on the determination of the first intensity minimum in intensity-voltage characteristics. This method provides a simple expression for determining the electro-optic coefficient given values for the ordinary and extraordinary refractive indices, the modulator geometry, and the first half-period voltage. The first half-period voltage is found to be approximately inversely proportional to the square root of the electrode length. The method shows close agreement to the exact Jones matrix method for the case where the sum of the principal refractive indices in one arm of Mach-Zehnder interferometer is close to that of the other arm under an electric field.

Transition Phenomenon in Salt-Doped Organic Electroluminescent Devices at High Bias Voltage

Organic electroluminescent (EL) devices using molecularly dispersed poly(N-vinylcarbazole) (PVCz) exhibit an irreversible transition phenomenon with a simultaneous and remarkable improvement in carrier injection at high bias voltage by doping with ammonium salt. The device structure used in this study was an indium tin oxide anode/PVCz:2,5-bis(1-naphtyl)-l,3,4-ox adiazole:coumarin 6:tetra-n-butylammonium tetrafluoroborate/metal cathode. The altered devices require significantly lower driving voltage and exhibit higher EL intensity compared with undoped devices. Furthermore, the EL intensity-voltage characteristics of the altered devices are independent of the work function of the cathodes.

Resonant-Tunneling-Injection Photoluminescence of Single InAs Self-Assembled Quantum Dots Embedded in a Thin AlGaAs Barrier

We have investigated resonant-tunneling-injection photoluminescence (PL) of single InAs self-assembled quantum dots (QDs) which were embedded in the barrier layer of an n-GaAs/i-AlGaAs/n-GaAs tunneling diode. A triangular structure in the PL intensity-voltage characteristics of a single PL line was observed. This reflects the electron tunneling from a three-dimensional emitter to the zero-dimensional quantum level of the QD. In addition, three subpeaks and a broad bulge of the PL were superimposed on the triangular structure. The subpeaks were ascribed to the resonant tunneling of holes into valence quantum levels of the QD. The origin of the excess PL bulge which is obtained at off-resonance bias condition is also discussed.

Non-linear contribution to intensity-voltage characteristics of gold nanowires

In this paper, we present experimental results for room temperature (I–V) characteristics of gold nanowires whose zero current conductance is quantized. We have analysed more throroughly the (I–V) characteristics of high stability nanoscopic gold contacts changing several parameters such as the formation technique (MCBJ, nanolithography, STM related technique) or the environment conditions around the nanowire (vacuum, air, polymer, non-conductive substrate). In all these experiments, a faster than linear increase of the current was observed, but at different threshold voltages depending on the situation: 0. 1V for “free standing” nanowires (in air or vacuum), 0.2 to 0.5V for non “free standing”, i.e., nanowires deposited on a substrate or embedded in a polymer.

Thin Films Photovoltaic Cells From Undoped And Doped Polyacetylene.

Abstract We realised thin film photovoltaic Cells by a direct polymerisation of (CH)X onto a sprayed (CH)x layer, The dark intensity-voltage characteristics are obtained for different temperatures and the capacity-voltage curves at different frequencies. The photovoltaic behaviour is studied. In spite of its low efficiency such junctions could lead, after improvment to very cheap photovoltaic cells.