There is a substantial amount of literature dealing with many aspects of synthesis and characterization of pure and doped binary compounds including Mn-doped ZnO which has been widely studied due to its superb properties as a dilute magnetic semiconductor (DMS). Aspects concerning doping limits for these compounds is an important stage in the search for new materials. Samples of Zn1-xMnxO nanocrystal were synthesized at temperatures of 180 °C and 200 °C using wet or liquid phase synthesis method. Dopant concentrations x=0.5, 1, 1.5, 2, 2.5, 5, 10, 20, 30, 40 and 50 per cent were studied. Powder x-ray diffraction (PXRD) patterns of the samples were analyzed with a view to determining the onset of secondary phases and hence the solubility limit of the dopant. The solubility limit for Mn in ZnO samples synthesized at temperature of 200 °C is realized at x <20%. For samples synthesized at temperature of 180 °C, the solubility limit is x <0.5%.

IntroductionIt is generally thought that countries that experience extended periods of sunshine might better enjoy the benefit of solar energy. Nevertheless, the performance of photovoltaic (PV) devices is critically dependent on the ambient temperature and the operating temperature of a given device. Also, irradiance, relative humidity and harmattan dust particles, and several other parameters such as wind speed, wind chill and direction, seasonal variation of sunrise and sunset, rainfall, and how the module is installed (rooftop, ground system, orientation, etc.) can be expected to influence the performance of a solar panel.Generally, sunny climates are most often hot, with a large variation in relative humidity, ranking from dry to humid. It is necessary, therefore, to carry out in situ studies of the parameters of PV devices under controlled and varying conditions. Such a study of the seasonal variation of the operating temperature of solar PV panels was undertaken in Southern Ghana.Ghana's climate depends on three types of air masses. Consequently, Ghana has three distinct types of climate (Varley and White 1958, 34-50):

IntroductionThe basic idea behind modelling a solar cell is to obtain the values of the operating parameters for the device. To that extent, the most popular of the existing models is the Shockley five-parameter model in which the equation governing the behaviour of the cell is formulated as a transcendental exponential equation involving five parameters, which are I L , the light-generated current, I s , the reverse saturation current, R s , the series resistance, R sh , the shunt resistance and T, the operating temperature.In the conventional approach to solving the fiveparameter model equation, it is often assumed that the light-generated current is most approximately equal to the short-circuit current. However, Da Rosa (2009, 552-553) has pointed out that in the presence of a large series resistance, there is a significant difference between the light-generated current and the short-circuit current due to the conversion of noticeable incident photon energy to heat.Different approaches to the solution of the equation have been developed. Several of these approaches have proved somewhat cumbersome (Hart 1982, 281-288; Lasnier 1990, 65-76). This paper discusses an alternative formulation of the model. This formulation leads to a relationship which allows an easy determination of the light-generated current.

Transparent conducting oxide material, ZnO nanoparticles has been synthesized using inexpensive and eco-friendly synthesis procedures with less or environmental pollutants and no liquid waste products. The effect of the temperatures on the structural properties for the synthesized ZnO nanocrystals has been investigated. In this study, we report an easy, low-cost, re-producible method for synthesizing ZnO nanoparticles by means of the liquid phase method. The ZnO nanocrystals were synthesized using the wet chemical route and the effect of temperature variation on the structural properties of investigated synthesized using powder x-ray diffractogram (XRD). The temperatures for the synthesis were varied from 120 °C to 200 °C in steps of 20 °C. The results show that, during the first stage of the synthesis of ZnO (at 120 °C), the XRD diffraction pattern confirms the cubic structure of zinc peroxide and the XRD pattern of the samples obtained at temperatures of 140 °C, 160 °C, 180 °C and 200 °C were confirmed to be hexagonal (wurtzite) crystal structure of ZnO. The XRD diffraction patterns of the 140 °C and 160 °C samples show some impurity phases which were associated with the zinc acetate by-product which is a colloid complex of water and methyl succinate and were removed by evaporation as temperatures were increased to 180 °C and 200 °C respectively. As temperature increases, the peak of the diffractograms of the sample becomes sharper and narrow indicating a decrease in width. A shift in peak positions to higher angles was observed and the positional parameter, bond angle, β, average crystallite size, APF, number of unit cells and density generally increase with temperature. However, the lattice parameters ‘a’ and ‘c’, bond lengths b and b1, bond angle, α, dislocation density, strain and unit cell volume were found to generally decrease with temperature.

No abstract