CW-Department of Physics

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Browsing CW-Department of Physics by Author "Musembi, R. J."

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    Analysis of Optimuzed Deposition Temperature of ZnO:Al Thin Film on SnSe ZnO:Al P-N Juction Solar Cell
    (2014) Munji, M. K.; Mbae, J. G.; Musembi, R. J.
    Solar energy has revolutionized the energy sector in the entire world by offering affordable, abundant and safe power source to the growing demands. The technology in solar cell production has advanced considerably in recent years Solar cell with very high conversion efficiency has been manufactured The efficiencies of solar cells depend on materials used. Deposition method and deposition conditions as they control the optoelectronic properties of the layers. Solar cell samples pre pared with a coat of ZnO)/AI exhibit 100 little degradation and very good solar cell properties (2hao et 01.,20(2). In this research Zinc Oxide will be doped in various percentages alluminurn ranging from 0% to 6% by mass to increase charge carriers. To obtain the optimum doping concentration, the optical and electrical properties of ZnO: AI thin film samples will be analyzed using a solid spec 3700 DUV optical spectrum analyzer and four point probe method respectively. The thin films of optimized Al doped 2nO will be deposited at different deposition temperature ranging from .4OOK-6OOK and tin selenide by reactive evaporation and evaporation technique respectively using Edward 306.Aulo evaporation system. The absorptance transrnittance and reflectance data of opitim ized ZnOA I in the range from 300nlll-2500nfll Will be obtained using UV-VIS NIR spectrophotometer solid state 3700 DUV. The resulting optical measurements will be analyzed using scout software to determine optical constant for thin solar cells The electrical properties of SnxSey and ZnO Al thin films w ill studied using four points probe method using Keithley 400 source meter using Lab View programme SnxSey-ZnO:AI solar cell will be fabricated using the optimized eloping concentration of AI and deposition temperature The performance of the p-n junction such as short circuit current (l sc). open circuit voltage (Voc ). fill factor (FF) and conversion efficiency (11) will be studied using a solar cell simulator
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    Effect of Sn Doping on the Electrical Properties of as Prepared and annealed ZnO thin films Prepared by Reactive Evaporation
    (2014) Munji, M. K.; Nyaga, P. K.; Musembi, R. J.
    Layers of transparent and conductive Sn-doped Zinc oxide (lnO) have been prepared by reacti. e evaporation on glass substrates. The deposition has been done at various doping levels ranging from J % to 8%. Annealing of samples was done using Rapid Thermal Processing (RTP). In this work, Nabertherrn Programmable Furnace system was used and annealing done at 300°C for one hour. Electrical characterization has been done for both prepared and annealed samples using four point probe configuration at room temperature (25°C) to obtain the sheet resistance. The sheet resistance for tin doped zinc oxide reduced with increase in tin doping to a minimum of J J .920cm at 4% tin doping for as prepared samples and I I .890cl11 for annealed samples.
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    Optimization of Sn.Se, Deposited by Reactive Thermal Evaporation for Solar cell Application
    (2014) Njoroge, W. K.; Munguti, L. K.; Musembi, R. J.
    Abstract In this study, tin selenide was prepared at different ratios using tin and selenium pellets in glass tube filled with argon and then heated up to 350'C. The resulting materials were cut Into ingots which were used in preparation of thin films by thermal evaporation. The evaporation was done using Edwards auto 306 coating unit. The chamber pressure was maintained at 5.0 x 10"mbars during the film deposition. Thin films of tin-selenide produced using various ratios were characterized for optical properties and sheet resistance. The optical measurements were done using UV-VJS-NIR spectrophotometer Solid State 3700 DUV in the visible range (380-750nm) and the transmittance spectra data obtained was analyzed using the SCOUT software. The films with ratio of J.I showed the highest transmittance of 85% with a band gap energy obtained 3S 140eV. The electrical characterization measurements were carried out using a four point probe at room temperature (25°(,) to obtain the sheet resistivity. The value of resistivity for was 20.1 .oem.
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    Optoelectronic Properties of Palladium Doped Tin (IV) Oxide (Pd: Sn02) Tlfin Films Deposited by Spray Pyrolysis
    (2013) Munji, M. K.; Mwathe, P. M.; Musembi, R. J.; Odari, B.V.
    Palladium Doped Tin (lV) Oxide (Pd: Sn02) thin films were deposited by Spray Pyrolysis technique using an alcoholic precursor solution consisting of Stannic chloride (SnCl~.5H20) and Palladium Chloride (PdCI?j The effect of increasing palladium concentration 011 optical and electrical properties was investigated. Sheet resistivity of the thin films was measured using the four point probe method and laid in the range of 0027- 3.43 Dcm for Pd: SnO:, thin films with Pd content of 0 - 6931% Pd prepared under optimized conditions. The optical properties were studied ill the UV/V1SiN1R region The Optical Band gap of the thin films was ill the range of3.73 - 4.11 eV