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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 62 (1996), S. 181-185 
    ISSN: 1432-0630
    Keywords: 72.70 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Heterojunctions, such as ZnO/CdS/CuGaSe2, were fabricated for photovoltaic applications. Optimization of device structures based on monocrystalline CuGaSe2 led to the highest-to-date power conversion efficiencies for CuGaSe2 solar cells. At room temperature under 100 mW/cm2 AM1.5 illumination a maximum cell efficiency of 9.7% was achieved, given by an open-circuit voltage of 946 mV, a short circuit current density of 15.5 mA/cm2, and a fill factor of 66.5%. Preparation and performance of the optimum device are described. Current voltage characteristics dependent on illumination intensity and temperature, spectral response and electron-beam-induced current measurements were performed to determine the device parameters as well as to analyse the current transport and loss mechanisms. Tunneling, assisted by defect levels in the CdS layer, seems to play a major role. High injection effects are observed at forward bias ofV 〉 0.5 V or an illumination level ofP 〉 10 mW/cm2. Under such conditions, as well as at low temperatures, the non-zero series resistance comes into play. Effects of the shunt resistance, however, are negligible in all cases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Crystal surfaces of the layered dichalcogenide semiconductor rehenium disulphide (ReS2) grown by the vapour-phase transport technique were investigated by combined atomic force microscopy (AFM), lateral (—friction) force microscopy (LFM) and force modulation (—local elasticity) microscopy as well as scanning electron microscopy (SEM). The as-grown crystals exhibit atomically flat surfaces, on which circular islands with a typical diameter of 0.3 μm and a height of 30-50 nm have grown. While AFM only yields the topographic information, the simultaneously recorded lateral force and force modulation images give a clear material contrast, showing that on the islands the lateral forces are higher and the local elasticity is lower than on the bare ReS2 surface. The dependence of both the topographic and the lateral force images on the scanning direction is investigated. The results indicate that during crystal growth a different material, presumably ReBr3, has segregated on the surface of the ReS2 crystals. It is demonstrated that AFM in combination with LFM and force modulation microscopy can provide information on the composition of heterogeneous samples as well as the local mechanical properties of the different components.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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