Diode Reverse Saturation Current Research Articles

Solar Cell Modeling and Parameter Optimization Using Simulated Annealing

This paper develops a unique solar cell modeling approach that incorporates search and optimization techniques for the determination of equivalent circuit parameters. In particular, simulated annealing is applied to automate the procedure of finding near-optimal values of the solar cell under various environmental settings. Photocurrents, diode reverse saturation currents, diode ideality factors, series resistances, and shunt resistances involved in the cell structure and parameters can be identified this way for every operating condition in an accurate modeling of the cell behavior. The developed models are evaluated for a set of solar cells, and their accuracy is verified by comparing the I=V curves generated from computer simulations with those provided by the cell manufacturer or determined experimentally. In addition, an algorithm has also been presented to use this model in solar array simulation under varying environmental conditions.

A rapid MPPT algorithm based on the research of solar cell's diode factor and reverse saturation current

An efficient Maximum Power Point Tracking (MPPT) algorithm is important to increase the output efficiency of a photovoltaic (PV) generate system. The conventional method have some problems in that ...

Modelling and experimental verification of the operating current of mono-crystalline photovoltaic modules using four- and five-parameter models

This article presents the modelling and experimental verification of the operating current of a 120 W of mono-crystalline photovoltaic module using four- and five-parameter analytical models. The southern part of Turkey, where the experimental system is mounted, is particularly well suited to photovoltaic installations. The operating current of the photovoltaic module, calculated from the models, is validated based on a series of experimental measurements. As well as the current and voltage of the photovoltaic module, the environmental variables such as ambient temperature and solar irradiance were measured and used for validation of the operating current. The photovoltaic cell models considered in this article are drawn from the equivalent electrical circuit that includes light-generated current, diode reverse saturation current, and series and shunt resistances. The simplified four-parameter model assumes the shunt resistance as infinite and thus neglects it. After determining the model parameters, the operating current is calculated using both models and compared to the measured current produced by the photovoltaic module. It is shown that the complete five-parameter model predicts the operating current better than the simplified four-parameter model, especially around solar noon, when most of the power is produced.

Deep level defects in GaAs on Si substrates grown by atomic hydrogen-assisted molecular beam epitaxy

The electrical activity of defects in GaAs p+n diodes grown on Si and GaAs substrates by both conventional molecular beam epitaxy (MBE) and atomic hydrogen-assisted MBE (H-MBE) were characterized by deep level transient spectroscopy. The well-known electron traps typical of MBE-grown GaAs were detected without the presence of any new levels in the upper half of the band gap. The trap densities and diode reverse saturation currents are significantly reduced in the homoepitaxial GaAs grown by H-MBE compared to that grown by MBE. The trap densities for the heteroepitaxial GaAs-on-Si grown by H-MBE have values higher than those of homoepitaxial GaAs grown by H-MBE at 330 °C, which are possibly affected by the residual dislocation density and stress. The reduction of trap density is attributed to in situ passivation of these defects by atomic H during the growth.

Photoelectrochemical investigations on particulate ZnO thin film electrodes in non-aqueous solvents

This particulate films of ZnO prepared from its ultrafine colloidal particles obtained by the sol-gel technique were studied as photoelectrodes in non-aqueous photoelectrochemical cells. With the use of non-aqueous (acetonitrile and propylene carbonate) electrolytes, higher photovoltage and photocurrent were observed as compared with those obtained with aqueous electrolyte. In propylene carbonate medium the particulate ZnO thin film electrode exhibited an almost ideal current-potential characteristic. By measuring the open-circuit photovoltage ( V oc) and short-circuit photocurrent ( i sc) as a function of monochromatic light ( λ = 360 nm) intensity, the diode quality factor ( n) and reverse saturation current ( i o) were evaluated as n = 1.5 and i o = 0.75 nA in propylene carbonate medium and i o = 2.6 nA in acetonitrile electrolyte. The Mott-Schottky plots for particulate ZnO thin film electrodes were found to be non-linear, so the flat-band potentials in various solvents were determined using the approximated Gartner equation (i.e. from the i photo 2 vs. V curve). Transient photocurrent-time profiles were also determined in various solvents using white light as well as monochromatic light for irradiation of the working electrode. The incident photon-to-current conversion efficiency (IPCE) at the peak wavelength ( λ = 360 nm) was found to be 27%, 24% and 14% in propylene carbonate, acetonitrile and aqueous electrolytes respectively, indicating clearly the advantage of non-aqueous solvents. The power conversion efficiency of the cell was found to vary with a change in counterelectrode and electrolyte medim. A high power conversion efficiency of about 1.8% was found in the case of propylene carbonate medium and carbon counterelectrode for monochromatic incident light ( λ = 360 nm). The fill factor in this case was 0.49.

Device physics of TRAPATT oscillators

This paper utilizes a simplified physical model to describe TRAPATT (TRApped Plasma Avalanche Triggered Transit) operation. By yielding on computational accuracy, a complete high-efficiency device design is generated and the dependence of operation on physical parameters is elucidated. The extreme complexity of the precise differential equations describing TRAPATT operation has made the calculation of a single diode-circuit configuration a tour de force. However, by observing the important features of such a solution, a simplified approach giving realistic answers has been evolved. A theoretical device design has been evolved. This design provides device width and impurity density as a function of TRAPATT frequency, and indicates a decreasing degree of reach with increasing frequency. In addition, the explicit dependence of width and impurity density on the diode's reverse saturation current has been obtained. The launching of the avalanche zone through the diode, and, in particular, the limitations implicit in the recovery to a swept-out state, are of broad significance in other types of diodes, particularly p-i-n switches and snap diodes.

Theoretical Considerations Governing the Choice of the Optimum Semiconductor for Photovoltaic Solar Energy Conversion

The theory of the photovoltaic effect is used to predict the characteristics of a semiconductor which would operate with an optimum efficiency as a photovoltaic solar energy converter. The existence of such an optimum material results from the interaction between the optical properties of the semiconductor which determine what fraction of the solar spectrum is utilized and its electrical properties which determine the maximum efficiency of conversion into electricity. Considerable attention is devoted to the effect of the forbidden energy gap (EG) of the semiconductor. It is shown that atmospheric absorption causes a shift in the solar spectrum which changes the value of the optimum forbidden energy gap between the limits 1.2 ev<EG <1.6 ev. Furthermore, plausible departures of the diode reverse saturation current (I0) from the parametric dependence predicted by Shockley are considered, and it is shown that such departures reduce the advantage of the optimum material over others in the range 1.1 ev<EG<2.0 ev. The relation between EG and the load impedance for maximum power transfer from the solar converter is discussed. Finally, I0 is computed from the published values of the semiconductor parameters of three intermetallic compounds, i.e., InP, GaAs, and CdTe, and it is shown that the efficiencies predicted for these materials are greater than those predicted for other materials which have been proposed, i.e., Si, CdS, Se, and AlSb.