Magnesium doped thin films of CuCrO2 and CuAl0.5Cr0.5O2, both exhibiting delafossite structure, were synthesized via sol-gel processing. The influence of the dopant on the phase development during the subsequent 2-step annealing procedure was monitored by X-ray diffraction. Systematic variation of the dopant concentration between 2.5 and 15% revealed that the Mg inhibits crystallization and stabilizes spinel phases against thermal decomposition, whereby the amount of impurities in the delafossite films is increased. Nevertheless the p-type conductivity and surprisingly the transmittance of the CuCrO2 films were improved by Mg doping by two orders of magnitude and 16%, respectively. On the contrary the performance of the CuAl0.5Cr0.5O2 films hardly profits from Mg doping. The Seebeck-coefficients of this system even imply a decreasing charge carrier density with increasing dopant concentration, which can only be interpreted as an expulsion of the native defects acting as strong intrinsic doping. The band gap of both oxides remains constant, however

We present an enhanced method to form stable dispersions of medium-sized silicon nanoparticles for solar cell applications by thermally induced grafting of acrylic acid to the nanoparticle surface. In order to confirm their covalent attachment on the silicon nanoparticles and to assess the quality of the functionalization, X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier spectroscopy measurements were carried out. The stability of the dispersion was elucidated by dynamic light scattering and Zeta-potential measurements, showing no sign of degradation for months.

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We report on the observation of a surprisingly high specific capacitance of β-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with β-FeSi2 particles by drop or spin casting. The β-FeSi2-nanoparticles, with crystallite sizes in the range of 10–30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3–4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.