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Abstract: Impedance measurements at wet chemically etched n-Si(111):H surfaces in contact with the aqueous electrolyte 0.1M H2SO4 reveal a surface state related capacitance extending over a potential range of 350mV in the n-Si(111):H band gap. A detailed analysis of the impedance data allows to identify three different surface state energy levels contributing to the observed surface state capacitance. These energy levels coincide with electronic states of hydrogen interdiffused into the n-Si(111):H subsurface region, which occurs, for example, during the wet chemical preparation of n-Si(111):H surfaces. The density of the observed states in the n-Si(111):H subsurface region is of the order of (1014–1015)cm−3. [Copyright &y& Elsevier]

Abstract: Stable and efficient organic solar cells with Mg (20 at. %): Ag alloy cathodes and bulk-heterojunction absorber layers from metal (e.g., Cu, Zn)-phthalocyanine and C60 small molecules are demonstrated. Device efficiencies of 4.0% under an illumination of 100 mW/cm2 at 25̊C were achieved as a result of the fine adjustment of the cathode work function as well as of the absorber design. By combining low and high work function materials, the work function in both Mg/Ag bilayer and Mg:Ag alloy layer cathodes was adjusted for optimum photovoltaic parameters. The electric and photovoltaic properties of the devices are discussed with respect to the cathode layer structure. The formation of the absorber/cathode interface was investigated by x-ray photoelectron spectroscopy measurements (XPS). The work function of the absorber and cathode layers were determined from the XPS high binding energy cutoff (HBEC) spectra. For optimized devices, the work function of the cathode at the side adjacent to the absorber layer equals 4.0…4.1 eV. While devices with Mg/Ag bilayer contacts exhibit a 65% efficiency drop in the first month after the preparation, devices with Mg:Ag alloy contacts demonstrate stable photovoltaic parameters within the time of the study of ∼ 1 year. [Copyright &y& Elsevier]

Abstract: Electrochemistry provides unique features for the preparation of low-dimensional structures, but in situ spectroscopy with atomic/molecular resolution at such structures is at present not well established yet. This paper shows that in situ scanning probe spectroscopy at solid/liquid interfaces can be utilized to study electronic properties at nanoscale, if appropriate conditions are applied. Tunneling spectroscopy provides information about tunneling barrier heights and electronic states in the tunneling gap, as shown on Au(111) substrates, contact spectroscopy allows for transport measurements at single nanostructures, as shown at Au/n-Si(111) nanodiodes. The influence of the electrolytic environment on spectroscopic investigations is not a principal limitation, but offers additional degrees of freedom, which allow, for example, spectroscopic studies of potential dependent surface phenomena at solid/liquid interfaces. [Copyright &y& Elsevier]