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International audience; The exciton blocking layer (EBL) as an interfacial layer is extremely critical in determining the organic photo-voltaic cell (OPV) performances. Here, we studied inverted planar heterojunction solar cells PHJ-OPVs with the following configuration ITO/EBL/C60/CuPc/MoO3/Al. Upon the EBL functionality which can act as an exciton blocking layer and allows the electron collection at the cathode, we proposed the insertion of hybrid EBL con -sisted of KI/Alq(3) thin layer. The Alq(3) is known as an EBL due to its broad bandgap, whereas we found that when a thin layer of 1 nm of KI is introduced in ITO/Alq(3) interface, the KI decomposed during the thermal deposition, and only potassium interacts and diffuses in the Alq(3) layer, which effectively enhances the electrons collection at the ITO/C-60 interfaces leading to the improvement of open-circuit voltage (Voc), and device power conversion efficiency by 36% than the device using Alq(3) alone as EBL.

The impact ionization in semiconductor materials is a process that produces multiple charge carrier pairs from a single excitation. This mechanism constitutes a possible road to increase the efficiency of the p-n and p-i-n solar cells junctions. Our study considers the structure of InN/InGaN quantum dot solar cell in the calculation. In this work, we study the effect of indium concentration and temperature on the coefficient θ of the material type parameter of the impact ionization process for a p(InGaN)-n(InGaN) and p(InGaN)-i(QDs-InN)-n(InGaN) solar cell. Next, we investigate the effect of perturbation such as temperature and indium composition on conventional solar cell’s (p(InGaN)-n(InGaN)) and solar cells of the third generation with quantum dot intermediate band IBSC (p(InGaN-i(QD-InN)-n(InGaN)) by analyzing their behaviour in terms of efficiency of energy conversion at the presence of the impact ionization process. Our numerical results show that the efficiency is strongly influenced by all of these parameters. It is also demonstrated that θ decreased with the increase of indium concentration and temperature which contributes to an overall improvement of the conversion efficiency.

In this work, a numerical study using radial basis functions (RBF) is performed on a Open image in new window-i-Open image in new window junction GaAs solar cell. So, we solve the differential equations satisfied by the density of excess photogenerated minority carriers in the front and rear regions of this junction. We observe the effect of back surface recombination velocity on the minority carrier distribution and the internal quantum efficiency (IQE) in the p type and n type regions. Next, we study the effect of insertion into the i region multiple of InGaAs/GaAsP quantum wells (QWs) with ultra-thin GaAs spacers inserted between the QW and the barriers. Precisely, we focus attention on the effect of In content and the number of QWs on IQE.

In this work we describe the physical properties of the organometallic thin films. We investigate the optical properties of the Bis-(8-hydroxyquinoline) magnesium (Mgq 2 ) thin film grown by Physical Vapor Deposition on glass substrate. Spectral properties of these films were examined using classical and time-dependent photoluminescence investigations. We found that the Mgq 2 thin films have a strong luminescence intensity while measuring in room temperature, however, this intensity decrease in the temperature range from 33 K to 300 K.

We report a theoretical investigation of the photovoltaic conversion efficiency of solar cells based on the introduction of I n x G a 1 − x N / I n N quantum dot supracrystals arrayed in the i-region of a p − i − n photodiode. The position and width of intermediate bands induced by the discrete quantized energy levels of electrons and holes originating from QDs are determined by using the Kronig-Penney model. Thus, interband and intersubband transitions are determined for different dot sizes and inter-dot distances. Taking into account the hole level and its impact on the band offset usually neglected in the same studies, all characteristic parameters of the cell such as open circuit voltage, short circuit current density and photoelectric conversion efficiency are determined as a function of the I n -concentration, mean size and inter-dot spacing of QDs. The results show that the performances of this new generation of solar cell increase considerably and can be adjusted by controlling the size, inter-dot spacing and I n -concentration.

In this paper, we have investigated the structural and optoelectronic properties of A 2 S n B r 6 (A = K, Cs, and Rb) using the density functional theory with generalized gradient approximation (GGA) for potential exchange-correlation. The modified Becke-Johnson (mBJ) potential approximation is also used for calculating the optoelectronic properties of the material. The results show that the band structure of the perovskites A 2 S n B r 6 has a semiconductor behavior with direct bandgap at Γ-Γ direction and that they have strong absorptions, and low reflections. As a result, these compounds are light harvester competent for photovoltaic applications. The spectroscopic limited maximum efficiency (SLME) was used to calculate the efficiency η of the A 2 S n B r 6 double perovskite solar flat cells.

The main problem of the photovoltaic conversion device is that low energy photons cannot excite charge carrier to the conduction band, so that the concept of the quantum dot solar cell is proposed in the intrinsic region of the p − i − n structure. In this work, numerical simulation has been proposed using the Matlab software. We simulate and measure the effects of quantum dots size and temperature on efficiency of GaAs p − i − n structure solar cells incorporating quantum dots (QDs) InAs under illumination. The results show that the efficiency of p − i − n solar cell depend strongly on size of QDs and temperature.

Capacitance-voltage (C-V) have been mainly performed on single diode, have not yet been fully implemented for measuring multijunction (MJ) solar cells because a signal composed by different contributions of each subcell which are not easy to determine. We demonstrate how, using C-V technique, the parameters of each sub-cell through DualJunction (DJ) solar cells can be determined. In this work, we propose a new approach using simple model and C-V method to characterize and evaluate the properties of the subcells in a monolithic DJ stack by extracting the important values of physical parameters, specifically the doping level (N) and the built-in voltage Vbi. To reach this goal, first we have measured the C-V characteristic of global dual-Junction GaAs/Ge solar cells. After, we have used Matlab software assuccess fully sound way to reach the behaviour of every single subcell.

International audience; Recently, the new tunable optoelectronic devices associated to the inclusion of the single dopant are in continuous emergence. Combined to other effects such as magnetic field, geometrical confinement and dielectric discontinuity, it can constitute an approach to adjusting new transitions. In this paper, we present a theoretical investigation of magnetic field, donor position and quantum confinement effects on the ground state binding energy of single dopant confined in ZnS/CdSe core/shell quantum dot. Within the framework of the effective mass approximation, the Schrödinger equation was numerically been solved by using the Ritz variational method under the finite potential barrier. The results show that the binding energy is very affected by the core/shell sizes and by the external magnetic field. It has been shown that the single dopant energy transitions can be controlled by tuning the dopant position and/or the field strength.

We report here on the preparation, X-ray diffraction with Rietveld refinement, AC susceptibility measurements and effect of heat treatments in (Y1-xSmx)SrBaCu3O6+z. Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For each x, the [AO] treatment increases the orthorhombicity epsiv = (b -a) / (b + a) (for 0 les x les 1), T c (for x ges 0.4) and the distance d [Cu(1) - (Sr / Ba)] (decrease T c ) for x 0.5 . When x increase from 0 to 1, epsiv decreases with T c[O]. However, T c[AO] decreases with epsiv until x = 0.2 and after it increases by 6 K to 85 K for x = 1 [AO]. A remarkable correlations were observed between Tc(x) and the volume of the unit cell V (x) ; and between deltaT c(x) = T c[AO] - T c[O] and deltaepsiv(x). A combination of several factors such as decrease in d [Cu(1) - (Sr / Ba)]; increase in cationic and chain oxygen ordering; the number p sh(x) of holes by Cu(2) - O2 superconducting plans and in-phase purity for the [AO] samples may account for the observed data.

Electron or proton irradiations introduce recombination centers, which tend to affect solar cell parameters by reducing the minority-carrier lifetime (MCLT). Because this MCLT plays a fundamental role in the performance degradation of solar cells, in this work we present a new approach that allows us to get accurate values of MCLT. The relationship between MCLT in p -region and n -region both before and after irradiation has been determined by the new method. The validity and accuracy of this approach are justified by the fact that the degradation parameters that fit the experimental data are the same for both short-circuit current and the open-circuit voltages. This method is applied to the p + / n -InGaP solar cell under 1 MeV electron irradiation.

Ferroelectric liquid crystal (FLC) materials exhibiting the cholesteric (N∗), smectic A (SmA) and chiral smectic C (SmC∗) phases have been studied by electro-optical and dielectric investigations. In the dielectric measurements, we have studied the soft mode in the SmC∗ and SmA phases. From experimental data, we have evaluated the soft mode rotational viscosity and the electroclinic coefficient in the SmA phase. All results are discussed and compared with previous studies performed on other homologues of the same series. The main result is that the relaxation process, observed in N∗ phase for the C8, C10 and C11 materials and identified as a soft-mode-like mechanism, disappears for C12.

We report here on the preparation, AC magnetic susceptibility and resistivity measurements of LnSrBaCu3O6+z (Ln = rare earth = Eu, Sm, Nd). Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. In the normal state, the heat treatment [AO] reduced considerably the linear resistivity parameters indicating a diminution of the interaction of carrier charges with phonons. For each ionic radius r(Ln+3), Tc increases remarkably by 10 K, 6 K and 6 K to Tc[AO] = 78 K, 85 K and 87 K, respectively for Ln = Nd, Sm and Eu. Tc(chi') and Tc(p = 0) were in good agreement. There was a remarkable improvement in the shielding effect in the case of the samples [AO] at all T < Tc and for any applied field. An enhancement of the irreversibility line was observed due to the argon treatment. A remarkable correlation was observed between Tc(r) and the number psh(r) of holes by Cu(2) - O2 superconducting planes. A combination of several factors such as the ionic size of the rare earth, increase in cationic and chain oxygen ordering; psh and in-phase purity for the [AO] samples may account for the observed data.

We describe a way to obtain the degradation, induced by proton and electron irradiations, of solar cell parameters (short-circuit current, open-circuit voltage and maximum power) versus fluence, directly from the calculation of the characteristics of the cell and of the irradiation-induced recombination centres. The calculation can be performed for any energy of the irradiating particle and for any specific thicknesses and doping levels of the base and emitters. The validity of this approach is illustrated in the case of GaAs cells of different origins and extended to GaInP cells. It will allow us to deduce the degradation of multijunction cells.

We demonstrate how, using electroluminescence, the parameters characterizing the recombination center induced by irradiation in a solar cell can be measured. Because electroluminescence is able to provide information on an individual cell in a multijunction (MJ) cell device, independently of the others, we apply this technique to measure these parameters in InGaP/GaAs/Ge MJ cells. We then calculate the variations of the open-circuit voltage and short-circuit current of such cells versus fluence. The results are compared with experimental data obtained for 1 MeV electron irradiations.

Monolithically stacked multijunction solar cells based on III–V semiconductors materials are the state-of-art of approach for high efficiency photovoltaic energy conversion, in particular for space applications. The individual subcells of the multi-junction structure are interconnected via tunnel diodes which must be optically transparent and connect the component cells with a minimum electrical resistance. The quality of these diodes determines the output performance of the solar cell. The purpose of this work is to contribute to the investigation of the tunnel electrical resistance of such a multi-junction cell through the analysis of the current-voltage (J-V) characteristics under illumination. Our approach is based on an equivalent circuit model of a diode for each subcell. We examine the effect of tunnel resistance on the performance of a multi-junction cell using minimization of the least squares technique.

The simple and efficient method for the extraction of all the parameters of a solar cell from a single current-voltage curve under one constant illumination level based on the Lambert W function. On calculating the lsqcurvefit function with constraints, between the experimental current-voltage characteristic and a theoretical arbitrary characteristic based on Lambert W-function. It is significant to understand the effect of the light intensity and temperature on output performance of the crystalline solar cells. The effect of light intensity and temperature on performance parameters of mc-si and pc-si solar cells is discusses. The experiments have been carried out under a solar simulator for various intensity levels in the range 1-2.5 sun and 25-60°C, respectively. The experiment was carried out employing solar cell simulator with varying cell temperature at constant light intensity. The results show that cell temperature has a significant effect on the photovoltaic parameters and it controls the quality and performance of the solar cell. The maximum power and efficiency are found to be decreased with cell temperature and the temperature coefficient of the efficiency and maximum output power is found to be negative.

The defect responsible for the minority‐carrier lifetime in p‐type Czochralski silicon introduced by electron irradiation has been detected and characterized by deep‐level transient spectroscopy and spin‐dependent recombination. From the isotropic g value (2.0055), the defect is tentatively identified as a Si dangling bond originating from a vacancy cluster. Its energetic location in the gap is at 630 meV below the conduction band. The electron and hole cross sections and their variation with temperature have been determined, and found to account for the minority‐carrier lifetime of the material.

We propose the use of electroluminescence to measure irradiation-induced degradation of multijunction photovoltaic cells in order to probe the degradation of each individual junction. We illustrate the technique by studying the decrease of the luminescence of GaInP, GaAs and Ge junctions of a triple-junction solar cell produced by 1 MeV electrons for fluences corresponding to space conditions.

It has already been shown that there are defects in semiconductors for which the capture of an electron from the conduction band occurs via a band other than the lowest one. We show here that electron emission from such defects also occurs toward this higher band. This is illustrated in the case of the Te-associated DX center in ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As of various alloy compositions by a comparison between ionization energies measured in a situation of thermal equilibrium and during the process of emission. In that case, the barrier associated with electron capture varies with the alloy composition, since it depends directly on the band structure. The barrier height does not take its origin in the large lattice distortion around the defect. This has been verified by comparing the temperature dependence of the barrier height with a theoretical calculation of the capture by multiphonon emission.

We analyze electron capture on a defect that exhibits no electron-phonon interaction. In this case, capture occurs by a cascade mechanism via the defect excited states. In direct-band-gap materials, when the temperature is too high to allow the filling of the \ensuremath{\Gamma} excited states at the bottom of conduction band, capture takes place via the excited states of a higher band, provided that they are deep enough. Experimental evidence for capture via the excited states of the L and X bands is provided for several defects or impurities in InP, GaAs, and related alloys.