This work emp loys extracts fro m Walnuts, Rhubarb, and Po megranate as natural dyes for fabricat ion of dye-sensitized solar cells (DSSCs). ZnO nanoparticles with crystallite mean value 12 n m as confirmed fro m XRD data have been synthesized at pH 12. SEM p icture of the ZnO powder reveals ho mogeneous and well defined nanoparticles with size of about 15 n m. TEM micrograph shows that the powder has a porous agglomerate structure consisting main ly of spherical crystalline particles with about 15-20 n m diameter. ZnO films were deposited on Fluorinated Tin Oxide (FTO) coated glass sheets followed by sintering at 450℃. The samples were sensitized by soaking in the dye solution. A Graphite slab was used as a back electrode, and redo x was employed as an electrolyte. Each cell was illu minated with light intensities in the range 40,000-100,000 Lux to measure the photovoltaic parameters. The experimental results shows that the highest I sc value is obtained fro m the DSSC sensitized with Rhubarb extract while the highest V oc value is obtained from the DSSC sensitized with the Walnuts extract. The P max of the DSSC sensitized by the Walnuts extract is greater than those sensitized by Rhubarb and Po megranate ext racts. Moreover, the open circuit voltage V oc decay was found to closely fo llo w a pseudo single exponential form.

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In this article an approach based on the Lambert W function is applied to analysis of various types solar cells and solar modules at a given insolation level and temperature; it can be used to extract accurate values of the parameters of a solar cell/module using experimental data or information available from the datasheet. These parameters are the photocurrent I ph , the reverse saturation current Io , the diode ideality factor a , the series resistance Rs , and the shunt resistance R sh . The parameters Io , a , Rs , and R sh are calculated with the aid of 4 equations that can be solved simultaneously while increasing the value of I ph in small increments. The calculated parameters are found to be in good agreement with those obtained in the literature. The experimental data of various solar cells/modules devices are obtained from the literature. Some of these devices are silicon solar cells and modules in addition to organic and DSSC solar cells. The mathematical I − V characteristics and the mathematical P − V characteristics are found to be in good agreement with the experimental data.

We propose theoretically an improved spectroscopic ellipsometer to study the optical properties of solids. In this system, the polarizer and the analyzer are rotating synchronously in the same direction at a speed ratio 1:3. The light intensity received by the detector contains six Fourier coefficients, one dc and five ac. One can independently extract the ellipsometric parameters as well as the optical constants of a sample using any of six different sets of the Fourier coefficients. A comparison among these sets is presented to find the optimal set corresponding to the minimum percent error in the calculation of the real and imaginary parts of the dielectric function. The results from the simulated spectra of the complex refractive index of c-Si, ZnSe, and GaP are presented.

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