Influence of charge carrier mobility on the performance of organic solar cells

The power conversion efficiency of organic solar cells based on donor–acceptor blends is governed by an interplay of polaron pair dissociation and bimolecular polaron recombination. Both processes are strongly dependent on the charge carrier mobility, the dissociation increasing with faster charge transport, with raised recombination losses at the same time. Using a macroscopic effective medium simulation, we calculate the optimum charge carrier mobility for the highest power conversion efficiency, for the first time accounting for injection barriers and a reduced Langevin‐type recombination. An enhancement of the charge carrier mobility from 10^–8 m²/V s for state of the art polymer–fullerene solar cells to about 10^–6 m²/V s, which yields the maximum efficiency, corresponds to an improvement of only about 20% for the given parameter set. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of adding salt on ultrasonic atomization in an ethanol-water solution

Ethanol was enriched by ultrasonic atomization. Enrichment ratios were increased by adding salt to the ethanol solution. Different enrichment ratios were observed for different types of salts in a range of low ethanol concentrations. The enrichment ratio was significantly improved by adding K(2)CO(3) or (NH(4))(2)SO(4). It is concluded that this is due to enhanced interfacial adsorption of the ethanol. Addition of Na(2)CO(3) to the ethanol solution also enhanced the interfacial adsorption of the ethanol, but the effect was relatively small. Addition of NaCl to the ethanol solution did not enhance the interfacial adsorption of the ethanol.     

长寿命吸收过程对超快动力学过程测量的影响

使用飞秒时间分辨抽运-探测透射光谱技术,实验研究了GaAs体材料中光激发载流子的超快弛豫动力学的波长依赖.在相同的光激发载流子浓度和抽运/探测比时,发现760 nm和780 nm两中心波长处的瞬态透射变化延迟扫描信号出现负的和振荡的信号.与模拟计算结果对比,判定该实验瞬态信号是错误的.分析探测器输出波形,发现是由于反相波形导致的,而引起反相波形的原因在于样品中存在长寿命的吸收过程.指出通过提高探测器上的抽运/探测比能够矫正反相波形,从而获得正确的瞬态透射变化动力学.提高探测器上的抽运/探测比与目前的应尽量减小抽运光对探测器的散射贡献的观点是对立的.文章的研究结果对应用抽运-探测时间分辨光谱技术正确地测量超快瞬态动力学过程具有重要的参考价值. 关键词： 时间分辨抽运-探测透射光谱 饱和吸收 吸收增强 GaAs体材料     

Influence of negative-U centers on the temperature dependence of the carrier concentration in the normal HTSC phase

The temperature dependence of the hole concentration in high-temperature superconductors is considered in terms of the model of negative-U centers. It is shown that this dependence can be nonmonotonic due to the interaction of electron subsystems from the valence band with negative-U centers and the conditions necessary for this have been established. The results obtained are compared with experimental data on the Hall coefficient in cuprates.     

Influence of carrier cations on the intensity of spectral lines of microelements in atomic-emission spectral analysis

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 18–21, January, 1991.     

Influence of carrier correlations on the excitonic optical response including disorder and microcavity effects

A model study of the characteristic signatures of carrier-correlation effects on the excitonic differential absorption spectra in semiconductors is presented. Using an effectively one-dimensional tight-binding system Coulomb-induced carrier-correlations up to third-order in the optical field are treated without additional approximations. To illustrate the influence of the different many-body contributions excitonic differential absorption spectra are computed for various polarizations and pump-probe time delays. The simultaneous influence of energetic disorder and correlations on the differential absorption spectra is discussed. Also presented are numerical results for the case when the semiconductor system is placed inside a microcavity in the strong-coupling regime. It is shown that the correlations induce characteristic signatures in the normal mode spectra. Received 22 January 1999     

Effect of free carrier screening on the binding energy of D− centers in polar semiconductors

A calculation of the binding energy of a D^? center, defined as the energy required to remove one of the two electrons from the D^? center to infinity, in the presence of other free carriers is reported in polar crystals. It is assumed that the effective interaction between each of the two electrons and the positive ion is described by Thomas-Fermi potential. The effective interaction between the two electrons in polar crystals is, however, described by two recently proposed potentials. The binding energy of a D^? ion is calculated variationally in several polar crystals as a function of the screening parameter δ and the value of δ at which the binding energy goes to zero (D^? Mott transition) is determined. A possible experimental situations where this system may be studied is discussed.     

Influence of the carrier concentration on the optical absorption edge of n-CuInSe2

The absorption spectra of as-grown and copper-annealed n-CuInSe₂ samples were obtained at room temperature. A shift of the absorption edge to higher energy for the annealed sample as compared to its value in the as-grown sample, is observed in the measurements. This behaviour can be explained as due to the fact that n-CuInSe₂ becomes degenerate at relatively low electron concentration because of its small electron effective mass.     

Influence of the soft phonon mode on charge carrier hopping transfer in bismuth-containing layered ferroelectric ceramic oxides

Formulas and calculations explaining the experimental data on maxima frequency displacement for imaginary dielectric components in a low frequency range with a rise in temperature within the limits of the ferroelectric phase were obtained for the ceramic structure SrBi₂(W _x/2Ti _x/2Nb_{1 − x} )₂O₉. At the heart of our consideration lies our assumption of the interaction of jumping charge carriers with a soft phonon mode.     

Influence of side electric potential on hysteresis loop parameters and electric permittivity in the Rochelle salt

It has been shown that the application of an electric potential to relatively narrow side electrodes of a thin perpendicular parallelepiped Rochelle salt sample plate leads to the disappearance of the hysteresis loop. The effect is permanent and can be observed after the side potential disconnection. Moreover, a reduction of both zero-field longitudinal permittivity maxima at the critical points is visible then. A non-zero remanent polarization and a non-zero coercive field are then able to be observed only at temperatures higher than that of the lower critical point and lower than that of the upper critical one. No corresponding temperature shift in reduced permittivity maxima has been noticed. A transition to below the lower critical point for the next few hours does not lead to restoration of the original properties formerly lost during the side potential application in the ferroelectric phase. Such restoration is possible by annealing the sample above the upper critical temperature.     

Influence of charge carrier diffusion on the stability of a charged drop of a finite-conductivity liquid

A dispersion relation for the capillary oscillations of a spherical drop of a viscous incompressible liquid with a charge transfer finite rate is derived and analyzed with emphasis on the role of diffusion. It is shown that diffusion has the strongest influence on the stability of rapidly damped quasi-periodic motions of a low-conductivity liquid. The instability growth rate of capillary oscillations grows with the charge diffusion coefficient and decreases with rising conductivity of the liquid.     

Influence of gain saturation and carrier dynamic models on the modulation response of quantum well lasers

The main problem for creation of optical communication systems is how quickly the light intensity can be changed under radiation from a laser diode. The modulation capability of lasers with separate confinement heterostructure depends strongly on carrier transport and gain saturation phenomena. Nonlinear gain saturation model in connection with dynamic behavior at high-frequency modulation is discussed and peculiarities of application of a new dynamic model with partial differential equation for the carrier transport in SCH region are shown.     

Influence of dispersion on the physicochemical properties of metatitanic acid

Li₂TiO₃ and H₂TiO₃ samples with various degrees of dispersion were investigated by X-ray diffraction, NMR spectroscopy, and electronic microscopy. It was shown that H₂TiO₃ has a distinct structure and exhibits high sorption activity in relation to rare earth elements. The sorption activity of H₂TiO₃ grows due to the increase in specific surface of samples.     

Influence of the external noise intensity on the kinetics of ligands binding to receptors

The average, variance, correlation function and the spectral density of ligand–receptor complexes in the presence of the external Langevin noise are calculated and their characteristics are defined. The analysis of the experimental data using the formulas derived in this work enables one to obtain a new information on the process of forming of ligand–receptor complex, namely, the constants rates of formation and the decay of the ligand–receptor complex.     

Interaction of aconitine with bovine serum albumin and effect of atropine sulphate and glycyrrhizic acid on the binding

The interaction of aconitine with bovine serum albumin (BSA) and effect of atropine sulphate and glycyrrhizic acid on binding constant, binding sites, and conformation were studied in an aqueous buffer solution (pH 7.40) by ultraviolet absorption and fluorescence spectroscopy. The study results show that aconitine quenched the endogenous fluorescence of BSA via a dynamic quenching procedure. Predominant intermolecular forces between aconitine and BSA were hydrophobic interactions, which stabilized the complex of aconitine–BSA. The distance between the donor and acceptor was 2.62 nm. The conformation of BSA was investigated by synchronous fluorescence techniques, indicating that the microenvironment around tryptophan (Trp) residues was changed. Furthermore, with the addition of atropine sulphate or glycyrrhizic acid, binding constant and the number of binding sites of aconitine to BSA were decreased, and the conformation had no change, which provide an important theoretical support for aconitine detoxification by atropine sulphate and glycyrrhizic acid.     

Influence of nonequilibrium charge carrier recombination on the signal shape and magnitude in the photodeflection spectroscopy method under pulse excitation

A theory of signal shaping is proposed for semiconductor investigation by the method of photodeflection spectroscopy with pulse excitation that would take account of the influence of charge carrier recombination on the temperature distribution in the specimen. Quantitative computations are performed for silicon that demonstrate the change in PDS signal amplitude and shape when taking account of bulk carrier recombination. It is shown that taking account of the influence of bulk recombination discloses the possibility of obtaining additional quantitative information about the charge carrier lifetime in the specimen.Translated from Izvestiya Vysshikh Uchebnykh zavedenii, Fizika, No. 1, pp. 41–45, January, 1991.     

Influence of Sr doping on the free carrier absorption in high-T c superconductors La2−x SrxCuO4

The reflectance spectra of polycrystalline La_2–x Sr _x CuO₄ samples were investigated in the energy range between 50 meV and 4 eV in dependence of the Sr content. The spectra are attributed to free carrier absorption of the Drude type, superimposed by optical phonon excitations below 0.1 eV and intrinsic absorption above 1 eV. From the influence of Sr doping onto the plasma energy it is deduced that La_2–x Sr _x CuO₄ is ap-type conductor with a maximum carrier concentration of 2.0×10²¹ cm^–3 forx=0.15. The results are interpreted in terms of a Hubbard model with an empty upper and ap-doped lower Hubbard band with a width of 1.9 eV.