Showing 4 results for Ghorashi
M. Neghabi, A. Behjat, S.m.b. Ghorashi,
Volume 4, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 4, No. 2, Summer-Fall 2010)
Abstract
ZnS/metal/ZnS (ZMZ) nanomultilayer films with Au, Ag and Cu as a metal layer have been deposited on a glass substrate by thermal evaporation and then, were annealed in air at different temperatures from 100 to 300 ºC for one hour. Several analytical tools such as X-ray diffraction, four point probe and spectrophotometer were used to study the changes in structural, electrical and optical properties of the samples. XRD patterns show that the crystallinity of structures and also grain size of particles increases with increasing the annealing temperature. Improved electrical property (a sheet resistance of 7 Ω/sq for ZnS/Au/ZnS) and considerable improvement in the transmittance curves (86% maximum transmittance for ZnS/Au/ZnS) of the samples after heat treatment at 200ºC was observed. Also, the optical constants of the ZMZ multilayer samples were calculated from transmittance and reflectance measurements. The figure of merit was applied on the ZMZ coatings and the most suitable films and annealing temperature for the application as transparent conductive electrodes were determined.
Nayyereh Daroogheh, Elham Karimi, S.m. Bagher Ghorashi,
Volume 13, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 13, No 2, Summer-Fall 2019)
Abstract
In this study, a sol-gel peroxotungstic acid sol was employed to deposit tungsten oxide (WO3) films by the spin-coating technique. In view of smart window applications, electrochromic windows were then designed and fabricated using a thin tungsten oxide film. For this purpose, Glass/ FTO/ WO3/ electrolyte/ FTO/Glass could be of use due to its special structure that consists of an electrochromic layer (WO3) on a transparent conductor (FTO), an electrolyte containing Li+ cations, and a transparent conductor layer. A voltage was applied on the fabricated sample, which was later assesed for its transmission, switching speed, and coloration efficiency. An increase in the coloration efficiency from 87 cm2/C-1 to 99.1 cm2/C-1 was found associated with an increase in the deposition speed. Moreover, the increase in the deposition speed led to a decrease in the coloration and bleaching time duration from 11.4 s to 6.2 s and from 12.8 s to 5.2 s respectively. The results obtained on the thin film WO3 can be useful for electrochromic applications.
Elham Karimi, Seyed Mohamad Bagher Ghorashi, Maryam Hashemi,
Volume 14, Issue 1 (Winter-Spring 2020)
Abstract
Recently, organo–metal halide perovskites have attracted much attention of the scientific community relating to their successful application in the absorber layer of low-cost solar cells. However, enough is known about the material and device properties, to realize that much remains to be learned.
In this paper, the electrical and optical properties of perovskite solar cells are investigated
using the COMSOL Multiphysics simulation program. It is a study of the influences
of carrier diffusion length (L), dielectric constant (ε
r), the valence band offset (VBO) of absorber/hole transport materials (HTM) and illumination intensity on fill factor (FF), short-circuit current density(J
SC), performance (PCE), and open-circuit voltage(V
OC). Also, J-V characteristics are calculated for diff
erent ε
r values. The simulation results point to the great dependence of efficiency on the carrier diffusion length of absorber layers. It is shown that, to obtain a high rate of efficiency, the relative permittivity should not be higher than 45.
Asieh Nazari Mofrad, S.m. Bagher Ghorashi, Farhad Jahantigh,
Volume 15, Issue 1 (Winter-Spring 2021)
Abstract
One of the main challenges for perovskite solar cell (PSCs) structures is their high sensitivity to humidity and ambient temperature, which significantly lowers the lifespan of these devices. Low stability of this devices is considered one of the principal limitations to make them commercialized. To increase the stability of the solar cell is to encapsulate the solar cell. The encapsulation is to cover the device with a non-reactive material, which prevents the penetration of ambient moisture and increases the thermal stability of the cell. If the uncoated device is exposed to continuous incident light for several hours, its structure is damaged while encapsulated device has a longer duration time. Several methods have been proposed for encapsulating a perovskite solar cell. The principal strategy of these methods involves deposition of a thin layer of polycarbonate polymer on the perovskite solar cell structure, resulting in layers of the desired structure. After fabrication and encapsulation process, the order of the various layers are FTO / bl-TiO2 / mp-TiO2 / Perovskite (CH3NH3PbI3) / Spiro-OMETAD / Au / Polycarbonate Polymer. To increase the effective stability, the glass coating is placed on the polycarbonate polymer. After acquiring sufficient adhesion between the glass coating and the polymer layer on the structure of PSCs, UV epoxy is used to seal the whole structure. Having performed the encapsulation, the samples were exposed every day to 85% constant humidity and 85°C temperature for 10 hours and it was observed that the cell efficiency, under the mentioned conditions and after successive measurements, maintained to a high extent.
