Simulation of TiO2/CuO solar cells with SCAPS-1D software

HighlightsTheory of electrically driven single-photon sources based on color centers in silicon carbide p–i–n diodes.New method of determining the electron and hole capture cross sections by an optically active point defect (color center) from the experimental measurements of the single-photon electroluminescence rate and second-order coherence.The developed method is based on the measurements at the single defect level. Therefore, in contrast to other approaches, one point defect is sufficient to measure its electron and hole capture cross sections.Point defects in the crystal lattice of SiC, known as color centers, have recently emerged as one of the most promising single-photon emitters for non-classical light sources. However, the search for the best color center that satisfies all the requirements of practical applications has only just begun. Many color centers in SiC have been recently discovered but not yet identified. Therefore, it is extremely challenging to understand their optoelectronic properties and evaluate their potential for use in practical single-photon sources. Here, we present a theoretical approach that explains the experiments on single-photon electroluminescence (SPEL) of novel color centers in SiC p–i–n diodes and gives the possibility to engineer highly efficient single-photon emitting diodes based on them. Moreover, we develop a novel method of determining the electron and hole capture cross sections by the color center from experimental measurements of the SPEL rate and second-order coherence. Unlike other methods, the developed approach uses the experimental results at the single defect level that can be easily obtained as soon as a single-color center is identified in the i-type region of the SiC p–i–n diode.Graphic

Thermal emission of electrons and holes from the ${\mathrm{Fe}}^{2+}$-${\mathrm{Fe}}^{3+}$ level in ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As is investigated in detail. Iron is found to act as a recombination center in this material, since majority carrier emission is observed in n- and in p-type layers. The interaction of the Fe level with free carriers is strongly localized, resulting in statistical distributions of the apparent activation energy and the electron and hole capture cross sections due to the statistical distribution of the occupancy of the cation sites by indium and gallium ions. A detailed general model for carrier capture and emission of a recombination center in a ternary alloy as observed by deep-level transient spectroscopy (DLTS) is developed. The mean energy position of ${\mathrm{Fe}}^{2+}$-${\mathrm{Fe}}^{3+}$ is determined as 0.39\ifmmode\pm\else\textpm\fi{}0.02 eV above the valence-band edge. This value agrees perfectly with the prediction of the internal reference rule. The electron and hole capture cross sections are distributed over nearly two orders of magnitude, causing a shift of the DLTS peaks with filling pulse width and nonexponential refilling of the traps. The mean values at 250 K are ${\mathrm{\ensuremath{\sigma}}}_{\mathit{n}}$=8\ifmmode\pm\else\textpm\fi{}5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$ ${\mathrm{cm}}^{2}$ and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{p}}$=2\ifmmode\pm\else\textpm\fi{}1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}17}$ ${\mathrm{cm}}^{2}$ for the electron and hole capture cross sections, respectively.

The effect of different meteorological conditions on Schottky-barrier solar-cell outputs has been investigated, using a model for an n-type solar cell. Similar results to those for p-n junction cells have been obtained, namely that although the output power density is reduced, a much higher conversion efficiency is possible when the solar cell is illuminated with diffuse radiation. The effect of the density of interfacial states, and the metal work function, upon the J/V characteristics and on the conversion efficiency is shown to be an important feature of Schottky-barrier solar cells.

A highly sensitive, contactless defect characterization technique, temperature- and injection-dependent lifetime spectroscopy (TIDLS), is introduced. In this method, the injection-level-dependent carrier lifetime curves of a semiconductor are measured at various temperatures by means of an inductively coupled resonant circuit. In order to illustrate certain features of the TIDLS, the lifetime-limiting defect center in aluminum-doped Czochralski silicon is analyzed. It is shown that, compared to previous lifetime spectroscopy techniques, TIDLS not only determines the defect energy level with improved accuracy, but is also capable of determining the temperature dependence of the electron and hole capture cross sections. In addition, the method permits the separation between shallow and deep-level centers.

In order to reduce current leakage and improve electron transfer in solar cells, charge transport layers (CTL), mainly hybrid electron transport layers (h-ETL), are considered as a solution. In this research contribution, computational analysis using SCAPS-1D software is performed to explore the output photovoltaic parameters of a Sb2S3-based solar cell with h-ETL. No theoretical works on this configuration have been previously reported. The main objectives of the present work are to propose a h-ETL with good band alignment with the Sb2S3 absorber, high transparency, and Cd free; to mitigate the instability and cost issues associated with using Spiro-OMeTAD HTL; and to optimize the solar cell. Thus, we calibrated the J-V characteristics and electrical parameters of the FTO/(ZnO/TiO2)/Sb2S3/Spiro-OMeTAD/Au solar cell by numerical simulation and compared them with those of the experiment. Subsequently, our simulations show that to replace the TiO2 ETL used in the experiment and to form the h-ETL with ZnO, IGZO is found to be a good candidate. It has better band alignment with the Sb2S3 absorber than TiO2 ETL, which reduces the trap states at the ETL/Sb2S3 interface; it has high transparency due to its wide bandgap; and an intense electric field is generated at the IGZO/Sb2S3 interface, which reduces the recombination phenomenon at this interface. MoO3, MASnBr3, Cu2O, CuI, and CuSCN HTL were also tested to replace the Spiro-OMeTAD HTL. Simulation results show that the cell with MoO3 HTL achieves higher performance due to its high hole mobility and high quantum efficiency in the visible region; it also allows the solar cell to have better thermal stability (TC=−0.32%/K) than the cell with Spiro-OMeTAD HTL (TC=−0.53%/K). The parameters that could improve the solar cell efficiency (η) obtained after these substitutions were also optimized. In particular, the parameters of the Sb2S3 absorber layer (thickness, defect density, and doping), ETL and HTL layer thicknesses, h-ETL/Sb2S3 interface defect density, and series and shunt resistances have been optimized. Finally, by combining high performance and thermal stability, the results show that the thermal stability of the solar cell depends on the back contact type; thus, nickel (Ni) was found to combine high performance and better thermal stability among the back contacts investigated. After these improvements, the efficiency of the Sb2S3-based solar cell increased from 5.08% (JSC=16.19 mA/cm2, VOC=0.56 V, and FF=55.40%) to 15.43% (JSC=18.51 mA/cm2, VOC=1.11 V, and FF=74.76%). This study proposes an approach to optimize the Sb2S3 upper subcell for tandem solar cells.

Capacitance and conductance measurements are presented for dc-driven Au/ZnS:Mn/p-Si electroluminescence metal-insulator-semiconductor (MIS) devices, where the ZnS:Mn films are deposited by radio frequency sputtering. Stable dc operation is achieved by introducing oxygen into the film during deposition and subsequently annealing. The effect of the post-deposition annealing upon the density of states at the ZnS:Mn/p-Si interface is investigated. As deposited, the devices show unusual MIS C-V characteristics, that indicate a very high interface state density. Annealing at 700 °C, normal C-V characteristics are observed, indicating that the very high density of states is greatly reduced. For these films the conductance technique has been used to measure the density of states at the interface between the ZnS:Mn and p-Si. The statistical model is found to describe most accurately the interface state conductance response. The interface state density consists of a tail of states that varies between 3.7×1013 cm−2 eV−1 at the silicon Fermi level and 1.1×1013 cm−2 eV−1 at the silicon mid-gap. A small peak is superimposed upon this tail at (−0.16±0.01) eV below mid-gap. The tail of states is believed to be intrinsic to the ZnS:Mn/p-Si interface, but evidence suggests that the small peak is due to the presence of oxygen, which is shown by secondary-ion mass spectrometry analysis to accumulate at the interface after annealing at 700 °C. It seems likely that the very high density of interface states in as deposited devices is a consequence of a plasma damage to the silicon surface during growth, creating defects such as silicon dangling bonds. One possible explanation for the decrease in this density is that by annealing at 700 °C, oxygen in the bulk of the film diffuses to the interface, where it mops up these defects by forming compounds such as SiOx. A simpler model of interface recrystallization is also suggested. The doping density in the depletion region of the silicon is calculated as (7.5±0.5)×1014 cm−3, and the interface state capture cross section for holes is found to have mean value of approximately 10−15 cm−2.

A great number of review articles have been devoted to the capture and ionization processes in collisions between multiply charged ions and atoms which play an important role in controlled thermonuclear fusion, astrophysics, and the development of short wavelength lasers, see for instance Invited Papers and Progress Reports at ICPEAC XI and ICPEAC XII1,2 , the IAEA Technical Committee Meeting on Atomic and Molecular Data for Fusion3, H.B. Gilbody4, A. Dalgarno5, Janev and Hvelplund6, A.V. Vinogradov and I.I. Sobel’man7 and R.W. Waynant and R.C. Elton8. In this paper we shall follow the scheme of a review article, which we have written three years ago9. There we discussed the experimental methods which have been used for the determination of electron capture and ionization cross sections and experimental results were given, which were compared with theory. The different behaviour of singly and multiply charged ions was explained and attention was given to the formation of excited states, decaying by photon or electron emission. Separate attention was given to experiments with atomic and molecular hydrogen as a target and to the scaling of electron loss and electron capture cross sections. In this paper we shall discuss the progress in the different fields of our previous paper9, further indicated by I. Therefore, it may be useful to use I as an introduction.

The second Born cross section for electron capture from a hydrogenlike atom of atomic number Z/sub T/ by a bare ion of atomic number Z/sub P/ and speed ..nu.. is evaluated for (Z/sub p/e/sup 2//h..nu..) very-much-less-than 1 and Z/sub T/ arbitrary. The ratio of the second to first Born cross sections increases rapidly as Z/sub T/ increases; for (Z/sub T/e/sup 2//h..nu..) > or approx. =1 this ratio is very large. These results indicate that second- and higher-order Born terms must be considered in calculating the cross section for inner-shell electron capture (or the time-reversed process).

Degradation behavior of CIGS solar Cells: A parametric analysis

Photoconduction of natural cinnabar (α-HgS)

Neutralization and ash products due to electron capture processes in plasmas reduce the efficiency of energy generation in fusion Tokamak reactors. Therefore, lithium ions have been used to improve the efficiency of energy generation where good control of the electron capture process is required. Here, we show that an intense ( W cm−2), ultra-short (1 fs at full width half-maximum) Gaussian laser pulse in the UV region can enhance the electron capture process on in the low collision keV energy region. We find a factor of 10 enhancement in electron capture cross-section at impact energies lower than 10 keV amu−1 for an 80 nm wavelength laser and a factor of 2 for the excitation process in the hydrogen atom as compared to the laser-free case. In contrast, for a 200 nm wavelength laser the increase of the electron capture cross-sections takes place around 1 keV amu−1 by a factor of 3 and no enhancement for the excitation process. Our results show that the UV assisted production of Li can be controlled, particularly for short UV wave-length for a specific collision energy range. We anticipate that our findings will facilitate UV laser control of the Li production in Tokamak reactors and encourage further experimental work in this system.

In this paper, the ionization and recombination coefficients of dense semiclassical hydrogen plasma on the basis of the effective interaction potential have been investigated. For this goal the Bohr – Lindhard method and method phase function have been applied to obtain the electron capture and ionization cross sections. The electron capture cross section has been calculated in the framework of the perturbation theory. The effective interaction potential, which takes into account the screening effects at large distances and quantum diffraction effects at short distances, was used. The results of the investigation show the behaviour of the calculated kinetic coefficients with a change in the plasma parameters: the ionization coefficient decreases with increasing density and (or) coupling parameter while the recombination coefficient increases.

Intensity enhancement of self-activated blue luminescence of ZnS phosphors by Mg 2+ions

Behaviour of an amphoteric defect under standard DLTS and beam injection DLTS, respectively

Characterization of charge injection and trapping in scaled SONOS/MONOS memory devices