Dark Depolarization Research Articles

Self-Aggregation-Controlled Rapid Chemical Bath Deposition of SnO2 Layers and Stable Dark Depolarization Process for Highly Efficient Planar Perovskite Solar Cells.

Planar perovskite solar cells (PSCs) incorporating n-type SnO2 have attracted significant interest because of their excellent photovoltaic performance. However, the film fabrication of SnO2 is limited by self-aggregation and inhomogeneous growth of the intermediate phase, which produces poor morphology and properties. In this study, a self-controlled SnO2 layer is fabricated directly on a fluorine-doped tin oxide (FTO) surface through simple and rapid chemical bath deposition. The PSCs based on this hydrolyzed SnO2 layer exhibit an excellent power conversion efficiency of 20.21 % with negligible hysteresis. Analysis of the electrochemical impedance spectroscopy on the charge transport dynamics indicates that the bias voltage influences both interfacial charge transportation and the ionic double layer under illumination. The hydrolyzed SnO2 -based PSCs demonstrate a faster ionic charge response time of 2.5 ms in comparison with 100.5 ms for the hydrolyzed TiO2 -based hysteretic PSCs. The results of quasi-steady-state carrier transportation indicate that a dynamic hysteresis in the J-V curves can be explained by complex ionic-electronic kinetics owing to the slow ionic charge redistribution and hole accumulation caused by electrode polarization, which causes an increase in charge recombination. This study reveals that SnO2 -based PSCs lead to a stabilized dark depolarization process compared with TiO2 -based PSCs, which is relevant to the charge transport dynamics in the high-performing planar SnO2 -based PSCs.

The Measurement of Intracellular Sodium Ion Concentration in the Horizontal Cells of the Stingray Retina

Membrane potentials, and intracellular concentrations of sodium ions in the horizontal cells of the stingray retina were measured directly by means of ion-selective microelectrodes. The electrodes used were of the double-barreled type and bis[(12-crown-4)methyl]methyldodecylmalonate was used as the ion-selective resin. The average intracellular concentration of Na+ ions in the horizontal cells and the extracellular concentration of Na+ ions near the horizontal cells were 123 mM and 351 mM, respectively (n = 27), The equilibrium potential was estimated to be +27·3 mV. Although each value of the equilibrium potential was scattered over a wide range, they were always positive regardless of the membrane potential. This was the first direct measurement of the sodium ion-concentration for the retinal horizontal cells. The results support the idea that the origin of the dark depolarization of the stingray horizontal cell is caused by the glutamate-induced high-sodium conductance of the membrane.

Ionizable groups and conductances of the rod photoreceptor membrane.

The ionizable groups and conductances of the rod plasma membrane were studied by measuring membrane potential and input impedance with micropipettes that were placed in the rod outer segments. Reduction of the pH from 8.0 to 6.8 or from 7.8 to 7.3 resulted in membrane depolarization in the dark from 8.0 to 6.8 or from 7.8 to 7.3 resulted in membrane depolarization in the dark (by 2- 3 mV) and an increased size of the light response (also by 2-3 mV). The dark depolarization was accompanied by and increased resting input impedance (by 11-35 Momega). When the pH was decreased in a perfusate in which Cl(-) was replaced by isethionate, the membrane depolarized. When the pH was decreased in a perfusate in which Na(+) was replaced by choline, an increase of input impedance was observed (11-50 Momega) even though a depolarization did not occur. These results are consistent with the interpretation that the effects of decreased extracellular pH result mainly from a decrease in rod membrane K(+) conductance that is presumably cause by protonation of ionizable groups having a pK(a) between 7.3 and 7.8. Furthermore, from these results and results obtained by using CO(2) and NH(3) to affect specifically the internal pH of the cell, it seems unlikely that altered cytoplasmic [H(+)] is a cytoplasmic messenger for excitation of the rod. When the rods were exposed to perfusate in which Na(+) was replaced by choline, the resting (dark) input impedance increased (by 26 Momega +/- 5 Momega SE), and the light-induced changes in input impedance became undetectable. Replacement of Cl(-) by isethionate had no detectable effect on either the resting input impedance or the light-induced changes in input impedance. These results confirm previous findings that the primary effect of light is to decrease the membrane conductance to Na(+) and show that, if any other changes in conductance occur, they depend upon the change in Na(+) conductance. The results are consistent with the following relative resting conductances of the rod membrane: G(Na(+)) similar to G(K(+)) more than 2-5 G(Cl(-)).

Prolonged depolarising afterpotentials in red-eyed Drosophila

After prolonged exposure to blue light, retinula cells R1 to R6 of white-eyed Drosophila remain depolarised in darkness. Long wavelength light (e.g. orange) reverts this dark depolarization. We have reproduced these results in red-eyed Drosophila (wild-type and cinnabar) by using whole field illumination. Even under these conditions, red-eyed flies require an order of magnitude more light than white-eyed flies. This is attributed to the presence of the screening pigment.

Photoinduced polarization properties of LilO_3 single crystal

Photoinduced polarization is achieved in a lithium iodate single crystal by the simultaneous application of a dc field and illumination from a uv source. The dark depolarization and photodepolarization current decay characteristics of the polarized samples have been studied in detail in this paper.

Investigation of time-dependent current inversion of the dark depolarization of the photoelectret state in polymorphic lead oxide

Investigation of time-dependent current inversion of the dark depolarization of the photoelectret state in polymorphic lead oxide

Electrophotographic processes using a dielectric layer bonded to a photoconductive layer as in the Katsuragawa process

With a photosensitive plate having a dielectric overcoating, an electrophotographic process available for repeated operation is developed. This process consists of three steps, utilizing the effect of photopolarization. An important feature is to allow the employment of higher photoconductive layers. As a result, high photosensitivity and high electrostatic contrast in electrophotography are achieved with this process. Factors determining the sensitivity are the rate of dark depolarization and light polarization and, in addition, the corona charging rate. This process may make possible applications in fields where only a slight exposure is allowed. What occurs in each step of this process is investigated analytically and experimentally.

Study of photoelectret phenomenon and dark depolarization current in evaporated semiconductor films of CdS

The photoelectret properties of vacuum evaporated CdS films on Pyrex glass plate have been studied. The deposition conditions were controlled to obtain high resistivity CdS films (resistivity of the order of 10 7 Ω cm). The photoelectret polarization was carried out by simultaneous application of electric field and white light illumination from tungsten lamp source. The polarization exhibits the linear dependence upon the polarizing voltage and polarizing time, with saturation effects for large values of these parameters. The polarization in films is found to be four orders of magnitude higher than the corresponding value in thick CdS crystals or powders. The dark depolarization current decay is very slow, and time for current, to decay to approximately half of its initial value varies between 1 and 8 min. This large decay time is correlated to the presence of deep trap levels in the CdS films. The study is of significance to improve the performance of thin film CdS devices.

Occurrence of Polarized Space Charge in Vapor Deposited Selenium Layers During Electrophotographic Processes

Persistent polarization due to polarized space charge in a selenium layer has been measured in combina-ation with corona charge and in relation to depositing condition. As the result, it has been found that intense persistent polarization can appear in the layer which depends upon vapor depositing and charging conditions. Furthermore, from measurements of the magnitude, dark depolarization, and photo-depolarization, some important results have been obtained on distribution of space charges, carrier injection, and carrier ejection in relation to the depositing condition. A process for latent image formation as well as for another observation of the persistent polarization without using the electrode is presented and analyzed. This analysis predicts the formation of an attractive latent image. A comparison between the analysis and an experiment has been made on selenium layers.

Schnelle photoelektrische Effekte der Alge Acetabularia

In the Alga Acetabularia intense light flashes produce transient depolarizing potentials which can be recorded intracellularly with 3 molar KCl glassmicroelectrodes. This rapid photoelectric effect has a latency of not more than 40 µsec. Spectral measurement showed a maximal sensitivity near 540 mµ. There is a second depolarization in the dark period after the flash. Lowering the temperature increases the amplitude of the fast depolarization and decreases the amplitude of the dark depolarization. Presumably the pigment and generator of the fast light-induced potential are associated with the cell membrane.