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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.03.003 Byline: F.M. Gaitho, F.G. Ndiritu, P.M. Muriithi, R.G. Ngumbu, J.K. Ngareh Keywords: Thermal conductivity; Single crystal silicon; Solar cell efficiency; Anti-reflective thin film Abstract: This paper presents the working of a single crystal silicon solar cell coated with a zinc oxide thin film. Single crystalline silicon is the absorber of incident solar radiation, while the zinc oxide film - an optically black film, offers optical improvement. Thermal conductivity measurements were made using the transient line heat source (TLHS) method, where the heat source is placed against the inner and outer surfaces of the solar cell to provide heating and to sense the temperature changes at the same time. In the temperature range 297-360K, values of thermal conductivities for the silicon material, zinc oxide and the surrounding air at atmospheric pressure were found to be 0.884-1.26x10.sup.3 Wm.sup.-1 K.sup.-1. By comparing the calculation results for the highest and lowest values of thermal conductivities, against the solar cell output, the value of collection efficiency for photo-generated carriers in the cell is seen to be varied. At moderate values of thermal conductivity - corresponding to mid temperatures, the cell output power and hence efficiency is observed to be high. Author Affiliation: Department of Physical Sciences, Masinde Muliro University of Science and Technology, P.O. Box 190, Kakamega-50100, Kenya Department of Physics and Computer Science, Egerton University, P.O. Box 536, Njoro, Kenya Article History: Received 11 May 2008; Revised 2 February 2009; Accepted 2 March 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Elias Stefanakos

Dynamical mechanical analysis yields information about the mechanical properties of a material as a function of deforming factors, such as temperature, oscillating stress and strain amplitudes. GaAs and Mn-doped GaAs at varied levels, used in making electronic devices, suffer from damage due to changes in environmental temperatures. This is a defective factor experienced during winter and summer seasons. Hence, there was a need to establish the best amount of manganese to be doped in GaAs so as to obtain a mechanically stable spin injector material to make electronic devices. Mechanical properties of Ga1-xMnxAs spin injector were studied in relation to temperatures above room temperature (25 °C). Here, creep compliance, Young's moduli and creep recovery for all studied samples with different manganese doping levels (MDLs) were determined using DMA 2980 Instrument from TA instruments Inc. The study was conducted using displace-recover programme on DMA creep mode with a single cantilever clamp. The samples were prepared using RF sputtering techniques. From the creep compliance study it was found that MDL of 10 % was appropriate at 30 °C and 40 °C. The data obtained can be useful to the spintronic and electronic device engineers in designing the appropriate devices to use at 30 °C and above or equal to 40 °C. [ABSTRACT FROM AUTHOR]

Plastic bags, mostly made of polyethylene, cause pollution as solid waste due to their nondegradable nature. Accelerated degradation, as a solution to mitigate the menace, can be achieved through moisture enhanced photolysis. This study evaluated the effect of three relative humidity environments, i.e., 25%, 40%, and 60% RH, at a constant temperature of 55°C. The effect was studied for ultraviolet (UV) irradiated and nonirradiated samples of polyethylene (PE) films processed under conventional ways. Photodegradation was initiated using ultraviolet irradiation in the ranges (200–300) nm and (300–400) nm for two hours and the effects of subsequent humidity treatment analyzed. Dynamic mechanical analysis was used to measure the dynamic storage modulus to monitor degradation. For nonirradiated samples, there was essentially no change in storage modulus at the three relative humidity environments after 550 hrs. Irradiation in the (300–400) nm range showed faster degradation than for the (200–300)nm range with the highest drop in storage modulus being 67% after 550 hrs. Raising the humidity from 25% to 40% and 60% RH resulted in 41%, 62%, and 67% drop of storage modulus, respectively, at the 550 hrs. [ABSTRACT FROM PUBLISHER]