The paper deals with investigation of electrical, structural and optical properties of very thin oxide/a-Si:H interfaces passivated by chemical treatment by KCN and HCN solutions. The oxide layers were prepared by thermal, chemical and plasma or ion beam assisted oxidations. Interface properties were evaluated by charge version of deep level transient spectroscopy, C-V measurements, X-ray diffraction (in both Bragg-Brentano and grazing incidence modes), optical reflectance (based on genetic algorithm) and photoluminescence. Considerable interest was devoted to distribution of three dominant groups of a-Si:H defect states in the band gap of the semiconductor as well as their response to bias annealing and light soaking experiments. We will present also dominant result - increase of the efficiency of a-Si:H based solar cells after chemical treatment. Finally, we will present the chemical passivation and oxidization as promising techniques suitable for applications in the field of nanotechnology.
Self-assembled monolayers (SAMs) have recently attracted much attention as a new methodology among a variety of thin film preparation. There have been several reports of fullerene SAM. These fullerene thin films seem to be the most promising candidates for realizing photovoltaic and optoelectronic devices at the nano-scale level. We have applied this technique to donor-linked fullerene systems and have developed supramolecular porphyrin-C60 molecules that are designed to be self-assembled on gold surface. Such systems are expected to mimic supramolecular photoinduced charge-separation events in photosynthesis. Porphyrin-linked C60 bearing a methylthio group was prepared by 1,3- dipolar cycloaddition of the azomethine ylide porphyrin with C60. SAM was formed by soaking Au electrode into a CH2Cl2 solution of the porphyrin-C60 dyad. Structure of the SAM was investigated by spectroscopic methods including X-ray photoelectron spectroscopy and ellipsometry and electrochemical studies. The large photocurrent with a level of sub-(mu) A/cm2 was observed for the photochemical cell in the presence of methyl viologen under illumination with approximately 10 mW/cm2. Possible mechanism for the photocurrent generation is discussed in terms of the photodynamics of porphyrin-linked fullerenes.
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