The project aims at exploring the use of nanovoids and nanodots prepared as plasmonic structures to enhance the efficiency of Si single-crystalline photovoltaic (PV) devices. Fabrication and experimental investigation of plasmonic structures in strained Si/SiGe multilayered structures will be carried to enhance light harvesting in solar cells due to both near-field and far-field effects. The main idea behind the production of nanovoids and nanodots is based on the ability of compressively strained thin SiGe alloy layers, incorporated in a Si matrix during epitaxial growth, to collect small-sized molecules (H, He, C) or vacancies, induced by irradiation. Further, thermal treatment results in the formation of nano-voids which are strictly assembled within the strained SiGe layers. The following key processes will be used: Molecular beam epitaxy of strained Si/SiGe/Si structures followed by irradiation with light ions (hydrogen, carbon) and rapid thermal treatment. This structure will then be additionally used as a template for segregation and self-assembling of metallic or carbon nanodots. The fundamental investigations of the structural, optical and electronic properties of the strained Si/SiGe layers will be carried out with a range of available methods for structural, electronical and optical characterization. By placing the nanovoids and nanodots in a highly doped emitter layer close enough to the p-n-junction that the near-fields will extend into the depletion layer, the effects of near-fields will be obtained. This will give a contribution to the electron-hole pair generation, and this will be additional to the far field effects. Being formed periodically, strained layers with self-assembled nanovoids or nanodots will display fundamentally unusual electronic and optical properties. These effects have not previously been experimentally studied in a solar cell configuration. The present system offers a unique configuration for such investigation.
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