S.N. Alamri

Modeling of photovoltaic module and experimental determination of serial resistance

Abstract An explicit model is presented for accurate simulation of the I-V curve characteristic of photovoltaic (PV) module. The model is compared with the traditional I-V curve characteristic and to some experimental results to show the accuracy of the method. The explicit model proposed is found to be reliable and accurate in situations where this model is a good approximation of cell or module performance. Also, an experimental method is presented to determine the series resistance and shunt resistance of the PV cells and PV modules.

A study on isothermal kinetics of glassy Sb9.1Te20.1Se70.8 alloy

Abstract In this research, the activation energy of amorphous Sb9.1 Te20.1 Se70.8 crystallization was studied under isothermal conditions using a differential scanning calorimetric (DSC) technique. The activation energy for Sb9.1 Te20.1 Se70.8 crystallization was determined to be 124 ± 4 kJ mol-1. The Avrami exponent was observed to decrease from 2.22 to 1.88 as the annealing temperature was increased from 413 to 421 K, and remained constant at higher temperatures. The local Avrami exponent was investigated and was observed to primarily indicate two-dimensional growth. The effects of annealing were revealed by studying the morphology of the samples with a scanning electron microscope (SEM).

Smart Windows with Different Thicknesses of V2O5 as Ion Storage Layers

Smart windows were fabricated with different thicknesses of amorphous V2O5, which acts as an ion storage layer. In these devices, V2O5 was deposited by thermal evaporation at a substrate temperature of 200 oC, and an electrochromic layer (WO3) was deposited by electron beam evaporation at a substrate temperature of 250 oC. Both layers were amorphous. V2O5 was found to exhibit direct-forbidden electron transitions, whereas the WO3 layer exhibited indirect-allowed electron transitions. An increase in the thickness of V2O5 from 78 nm to 313 nm reduced the colouration efficiency from 64 to 48 cm2/C, and the time of the transmission variation curve from the coloured state to the bleached state was increased from 82.41 s to 558 s.

Ammonia free growth of CdS thin films by Chemical Bath Technique

CdS thin films were deposited by a chemical bath deposition technique (CBD). The bath solution is composed of CdCl2 (0.1 M) salt as a source for Cd and thiourea (0.1M) as a source of sulphur (S). To avoid the toxicity and volatility of the commonly used ammonia, ethanolamine (ETA ) is used as complexing agent. Films were deposited with different times from 30 to 120 minutes in order to study the films growth mechanism. The solution temperature was fixed at 60°C. The structural and morphological films characterizations were carried by XRD analysis and AFM observations. From the XRD analysis we inferred that obtained CdS films have a pure hexagonal structure with the preferential orientation along the plane (101). The pure hexagonal structure is highly recommended for the realization of CdTe/ CdS or CuInSe/CdS solar cells. The presence of the hexagonal structure and the low growth rate in order of 1nm/min suggest that the growth mechanism is achieved through the ion by ion process. The optical characterizat...

Preparation of the Three Main Layers of CdS/CdTe Thin Film Solar Cells Using a Single Vacuum System

This study investigates the preparation of the three main layers of a CdS/CdTe thin film solar cell using a single vacuum system. A Close Space Sublimation System was constructed to deposit CdS, CdTe and CdCl2 solar cell layers. Two hot plates were used to heat the source and the substrate. Three fused silica melting dishes were used as containers for the sources. The properties of the deposited CdS and CdTe films were determined via Atomic force microscopy, scanning electron microscopy, X-ray diffraction and optical transmission spectroscopy. An J-V characterization of the fabricated CdS/CdTe solar cells was performed under solar radiation. The short-circuit current density, Jsc, the open-circuit voltage, Voc, fill factor, FF and conversion efficiency, η, were measured and yielded values of 27 mA/cm2, 0.619 V, 58% and 9.8%, respectively.

The hexagonal to discotic phase transition in 1,4,8,11,15,18,22,25‐octahexylphthalocyanine studied by differential scanning calorimetry

The phase change in metal‐free 1,4,8,11,15,18,22,25‐octahexylphthalocyanine compound with eight non‐peripheral hexyl chains was investigated under non‐isothermal conditions by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Two endothermic changes were reported. The first one between 332 and 350 K relates to the transition from the hexagonal columnar mesophase to a less ordered crystalline phase, P1. The second endothermic transition from 408 to 417 K is due to the transition to the discotic columnar mesophase, P2. The isoconversional methods of Friedman, and Kissinger, Akahira and Sunose (KAS) were used to determine the variation of the activation energy for crystallisation with temperature, E α(T). Using the Friedman method the average values of E α(T) were 121.31 and 352.77 kJ mol−1 for the first and second peaks, respectively. The KAS method gave higher values of E α(T) with averages of 173.25 and 411.44 kJ mol−1, respectively. The specific heat was measured and found to vary with temperature.

Structural and optical properties of 1, 4, 8, 11, 15, 18, 22, 25-octahexylphthalocyanine: A comparison between thermally evaporated and spin-coated thin films

Abstract Thin films of 1, 4, 8, 11, 15, 18, 22, 25-octahexylphthalocyanine were deposited on glass substrates by the thermal evaporation and spin coating techniques. The structure of the both types of films was found to be in a form. The crystallite size assumed the values of 88.65 and 44.32 nm for thermal and spin coated films, respectively. The surface morphology of the thin films was investigated by atomic force microscopy and showed that the molecules of 1, 4, 8, 11, 15, 18, 22, 25-octahexylphthalocyanine grew in stacks of parallel rows. The optical properties of thermally evaporated and spin coated films are reported here. The spectrophotometric measurements of transmittance and reflectance were carried out at UV-Vis-NIR region for the films that showed two absorption bands, namely the Q- and Soret bands. The mechanism of the optical absorption follows the indirect transitions. Almost there was no remarkable difference was observed between the two types of films. Other optical parameters, such as absorption coefficients α, the absorption index, k, and refractive index, n, were also determined.